rtlsdr library example compiles

1 files changed, 2023 insertions, 0 deletions

diff --git a/Radio/HW/RtlSdr/r820/src/librtlsdr.c b/Radio/HW/RtlSdr/r820/src/librtlsdr.c
new file mode 100644
index 0000000..2deb38c
--- /dev/null
+++ b/Radio/HW/RtlSdr/r820/src/librtlsdr.c
@@ -0,0 +1,2023 @@
+/*
+ * rtl-sdr, turns your Realtek RTL2832 based DVB dongle into a SDR receiver
+ * Copyright (C) 2012-2014 by Steve Markgraf <steve@steve-m.de>
+ * Copyright (C) 2012 by Dimitri Stolnikov <horiz0n@gmx.net>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <errno.h>
+#include <signal.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#ifndef _WIN32
+#include <unistd.h>
+#define min(a, b) (((a) < (b)) ? (a) : (b))
+#endif
+
+#include "libusb.h"
+
+/*
+ * All libusb callback functions should be marked with the LIBUSB_CALL macro
+ * to ensure that they are compiled with the same calling convention as libusb.
+ *
+ * If the macro isn't available in older libusb versions, we simply define it.
+ */
+#ifndef LIBUSB_CALL
+#define LIBUSB_CALL
+#endif
+
+/* two raised to the power of n */
+#define TWO_POW(n)		((double)(1ULL<<(n)))
+
+#include "rtl-sdr.h"
+#include "tuner_e4k.h"
+#include "tuner_fc0012.h"
+#include "tuner_fc0013.h"
+#include "tuner_fc2580.h"
+#include "tuner_r82xx.h"
+
+typedef struct rtlsdr_tuner_iface {
+	/* tuner interface */
+	int (*init)(void *);
+	int (*exit)(void *);
+	int (*set_freq)(void *, uint32_t freq /* Hz */);
+	int (*set_bw)(void *, int bw /* Hz */);
+	int (*set_gain)(void *, int gain /* tenth dB */);
+	int (*set_if_gain)(void *, int stage, int gain /* tenth dB */);
+	int (*set_gain_mode)(void *, int manual);
+} rtlsdr_tuner_iface_t;
+
+enum rtlsdr_async_status {
+	RTLSDR_INACTIVE = 0,
+	RTLSDR_CANCELING,
+	RTLSDR_RUNNING
+};
+
+#define FIR_LEN 16
+
+/*
+ * FIR coefficients.
+ *
+ * The filter is running at XTal frequency. It is symmetric filter with 32
+ * coefficients. Only first 16 coefficients are specified, the other 16
+ * use the same values but in reversed order. The first coefficient in
+ * the array is the outer one, the last, the last is the inner one.
+ * First 8 coefficients are 8 bit signed integers, the next 8 coefficients
+ * are 12 bit signed integers. All coefficients have the same weight.
+ *
+ * Default FIR coefficients used for DAB/FM by the Windows driver,
+ * the DVB driver uses different ones
+ */
+static const int fir_default[FIR_LEN] = {
+	-54, -36, -41, -40, -32, -14, 14, 53,	/* 8 bit signed */
+	101, 156, 215, 273, 327, 372, 404, 421	/* 12 bit signed */
+};
+
+struct rtlsdr_dev {
+	libusb_context *ctx;
+	struct libusb_device_handle *devh;
+	uint32_t xfer_buf_num;
+	uint32_t xfer_buf_len;
+	struct libusb_transfer **xfer;
+	unsigned char **xfer_buf;
+	rtlsdr_read_async_cb_t cb;
+	void *cb_ctx;
+	enum rtlsdr_async_status async_status;
+	int async_cancel;
+	int use_zerocopy;
+	/* rtl demod context */
+	uint32_t rate; /* Hz */
+	uint32_t rtl_xtal; /* Hz */
+	int fir[FIR_LEN];
+	int direct_sampling;
+	/* tuner context */
+	enum rtlsdr_tuner tuner_type;
+	rtlsdr_tuner_iface_t *tuner;
+	uint32_t tun_xtal; /* Hz */
+	uint32_t freq; /* Hz */
+	uint32_t bw;
+	uint32_t offs_freq; /* Hz */
+	int corr; /* ppm */
+	int gain; /* tenth dB */
+	struct e4k_state e4k_s;
+	struct r82xx_config r82xx_c;
+	struct r82xx_priv r82xx_p;
+	/* status */
+	int dev_lost;
+	int driver_active;
+	unsigned int xfer_errors;
+};
+
+void rtlsdr_set_gpio_bit(rtlsdr_dev_t *dev, uint8_t gpio, int val);
+static int rtlsdr_set_if_freq(rtlsdr_dev_t *dev, uint32_t freq);
+
+/* generic tuner interface functions, shall be moved to the tuner implementations */
+int e4000_init(void *dev) {
+	rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
+	devt->e4k_s.i2c_addr = E4K_I2C_ADDR;
+	rtlsdr_get_xtal_freq(devt, NULL, &devt->e4k_s.vco.fosc);
+	devt->e4k_s.rtl_dev = dev;
+	return e4k_init(&devt->e4k_s);
+}
+int e4000_exit(void *dev) {
+	rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
+	return e4k_standby(&devt->e4k_s, 1);
+}
+int e4000_set_freq(void *dev, uint32_t freq) {
+	rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
+	return e4k_tune_freq(&devt->e4k_s, freq);
+}
+
+int e4000_set_bw(void *dev, int bw) {
+	int r = 0;
+	rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
+
+	r |= e4k_if_filter_bw_set(&devt->e4k_s, E4K_IF_FILTER_MIX, bw);
+	r |= e4k_if_filter_bw_set(&devt->e4k_s, E4K_IF_FILTER_RC, bw);
+	r |= e4k_if_filter_bw_set(&devt->e4k_s, E4K_IF_FILTER_CHAN, bw);
+
+	return r;
+}
+
+int e4000_set_gain(void *dev, int gain) {
+	rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
+	int mixgain = (gain > 340) ? 12 : 4;
+#if 0
+	int enhgain = (gain - 420);
+#endif
+	if(e4k_set_lna_gain(&devt->e4k_s, min(300, gain - mixgain * 10)) == -EINVAL)
+		return -1;
+	if(e4k_mixer_gain_set(&devt->e4k_s, mixgain) == -EINVAL)
+		return -1;
+#if 0 /* enhanced mixer gain seems to have no effect */
+	if(enhgain >= 0)
+		if(e4k_set_enh_gain(&devt->e4k_s, enhgain) == -EINVAL)
+			return -1;
+#endif
+	return 0;
+}
+int e4000_set_if_gain(void *dev, int stage, int gain) {
+	rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
+	return e4k_if_gain_set(&devt->e4k_s, (uint8_t)stage, (int8_t)(gain / 10));
+}
+int e4000_set_gain_mode(void *dev, int manual) {
+	rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
+	return e4k_enable_manual_gain(&devt->e4k_s, manual);
+}
+
+int _fc0012_init(void *dev) { return fc0012_init(dev); }
+int fc0012_exit(void *dev) { return 0; }
+int fc0012_set_freq(void *dev, uint32_t freq) {
+	/* select V-band/U-band filter */
+	rtlsdr_set_gpio_bit(dev, 6, (freq > 300000000) ? 1 : 0);
+	return fc0012_set_params(dev, freq, 6000000);
+}
+int fc0012_set_bw(void *dev, int bw) { return 0; }
+int _fc0012_set_gain(void *dev, int gain) { return fc0012_set_gain(dev, gain); }
+int fc0012_set_gain_mode(void *dev, int manual) { return 0; }
+
+int _fc0013_init(void *dev) { return fc0013_init(dev); }
+int fc0013_exit(void *dev) { return 0; }
+int fc0013_set_freq(void *dev, uint32_t freq) {
+	return fc0013_set_params(dev, freq, 6000000);
+}
+int fc0013_set_bw(void *dev, int bw) { return 0; }
+int _fc0013_set_gain(void *dev, int gain) { return fc0013_set_lna_gain(dev, gain); }
+
+int fc2580_init(void *dev) { return fc2580_Initialize(dev); }
+int fc2580_exit(void *dev) { return 0; }
+int _fc2580_set_freq(void *dev, uint32_t freq) {
+	return fc2580_SetRfFreqHz(dev, freq);
+}
+int fc2580_set_bw(void *dev, int bw) { return fc2580_SetBandwidthMode(dev, 1); }
+int fc2580_set_gain(void *dev, int gain) { return 0; }
+int fc2580_set_gain_mode(void *dev, int manual) { return 0; }
+
+int r820t_init(void *dev) {
+	rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
+	devt->r82xx_p.rtl_dev = dev;
+
+	if (devt->tuner_type == RTLSDR_TUNER_R828D) {
+		devt->r82xx_c.i2c_addr = R828D_I2C_ADDR;
+		devt->r82xx_c.rafael_chip = CHIP_R828D;
+	} else {
+		devt->r82xx_c.i2c_addr = R820T_I2C_ADDR;
+		devt->r82xx_c.rafael_chip = CHIP_R820T;
+	}
+
+	rtlsdr_get_xtal_freq(devt, NULL, &devt->r82xx_c.xtal);
+
+	devt->r82xx_c.max_i2c_msg_len = 8;
+	devt->r82xx_c.use_predetect = 0;
+	devt->r82xx_p.cfg = &devt->r82xx_c;
+
+	return r82xx_init(&devt->r82xx_p);
+}
+int r820t_exit(void *dev) {
+	rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
+	return r82xx_standby(&devt->r82xx_p);
+}
+
+int r820t_set_freq(void *dev, uint32_t freq) {
+	rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
+	return r82xx_set_freq(&devt->r82xx_p, freq);
+}
+
+int r820t_set_bw(void *dev, int bw) {
+	int r;
+	rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
+
+	r = r82xx_set_bandwidth(&devt->r82xx_p, bw, devt->rate);
+	if(r < 0)
+		return r;
+	r = rtlsdr_set_if_freq(devt, r);
+	if (r)
+		return r;
+	return rtlsdr_set_center_freq(devt, devt->freq);
+}
+
+int r820t_set_gain(void *dev, int gain) {
+	rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
+	return r82xx_set_gain(&devt->r82xx_p, 1, gain);
+}
+int r820t_set_gain_mode(void *dev, int manual) {
+	rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev;
+	return r82xx_set_gain(&devt->r82xx_p, manual, 0);
+}
+
+/* definition order must match enum rtlsdr_tuner */
+static rtlsdr_tuner_iface_t tuners[] = {
+	{
+		NULL, NULL, NULL, NULL, NULL, NULL, NULL /* dummy for unknown tuners */
+	},
+	{
+		e4000_init, e4000_exit,
+		e4000_set_freq, e4000_set_bw, e4000_set_gain, e4000_set_if_gain,
+		e4000_set_gain_mode
+	},
+	{
+		_fc0012_init, fc0012_exit,
+		fc0012_set_freq, fc0012_set_bw, _fc0012_set_gain, NULL,
+		fc0012_set_gain_mode
+	},
+	{
+		_fc0013_init, fc0013_exit,
+		fc0013_set_freq, fc0013_set_bw, _fc0013_set_gain, NULL,
+		fc0013_set_gain_mode
+	},
+	{
+		fc2580_init, fc2580_exit,
+		_fc2580_set_freq, fc2580_set_bw, fc2580_set_gain, NULL,
+		fc2580_set_gain_mode
+	},
+	{
+		r820t_init, r820t_exit,
+		r820t_set_freq, r820t_set_bw, r820t_set_gain, NULL,
+		r820t_set_gain_mode
+	},
+	{
+		r820t_init, r820t_exit,
+		r820t_set_freq, r820t_set_bw, r820t_set_gain, NULL,
+		r820t_set_gain_mode
+	},
+};
+
+typedef struct rtlsdr_dongle {
+	uint16_t vid;
+	uint16_t pid;
+	const char *name;
+} rtlsdr_dongle_t;
+
+/*
+ * Please add your device here and send a patch to osmocom-sdr@lists.osmocom.org
+ */
+static rtlsdr_dongle_t known_devices[] = {
+	{ 0x0bda, 0x2832, "Generic RTL2832U" },
+	{ 0x0bda, 0x2838, "Generic RTL2832U OEM" },
+	{ 0x0413, 0x6680, "DigitalNow Quad DVB-T PCI-E card" },
+	{ 0x0413, 0x6f0f, "Leadtek WinFast DTV Dongle mini D" },
+	{ 0x0458, 0x707f, "Genius TVGo DVB-T03 USB dongle (Ver. B)" },
+	{ 0x0ccd, 0x00a9, "Terratec Cinergy T Stick Black (rev 1)" },
+	{ 0x0ccd, 0x00b3, "Terratec NOXON DAB/DAB+ USB dongle (rev 1)" },
+	{ 0x0ccd, 0x00b4, "Terratec Deutschlandradio DAB Stick" },
+	{ 0x0ccd, 0x00b5, "Terratec NOXON DAB Stick - Radio Energy" },
+	{ 0x0ccd, 0x00b7, "Terratec Media Broadcast DAB Stick" },
+	{ 0x0ccd, 0x00b8, "Terratec BR DAB Stick" },
+	{ 0x0ccd, 0x00b9, "Terratec WDR DAB Stick" },
+	{ 0x0ccd, 0x00c0, "Terratec MuellerVerlag DAB Stick" },
+	{ 0x0ccd, 0x00c6, "Terratec Fraunhofer DAB Stick" },
+	{ 0x0ccd, 0x00d3, "Terratec Cinergy T Stick RC (Rev.3)" },
+	{ 0x0ccd, 0x00d7, "Terratec T Stick PLUS" },
+	{ 0x0ccd, 0x00e0, "Terratec NOXON DAB/DAB+ USB dongle (rev 2)" },
+	{ 0x1554, 0x5020, "PixelView PV-DT235U(RN)" },
+	{ 0x15f4, 0x0131, "Astrometa DVB-T/DVB-T2" },
+	{ 0x15f4, 0x0133, "HanfTek DAB+FM+DVB-T" },
+	{ 0x185b, 0x0620, "Compro Videomate U620F"},
+	{ 0x185b, 0x0650, "Compro Videomate U650F"},
+	{ 0x185b, 0x0680, "Compro Videomate U680F"},
+	{ 0x1b80, 0xd393, "GIGABYTE GT-U7300" },
+	{ 0x1b80, 0xd394, "DIKOM USB-DVBT HD" },
+	{ 0x1b80, 0xd395, "Peak 102569AGPK" },
+	{ 0x1b80, 0xd397, "KWorld KW-UB450-T USB DVB-T Pico TV" },
+	{ 0x1b80, 0xd398, "Zaapa ZT-MINDVBZP" },
+	{ 0x1b80, 0xd39d, "SVEON STV20 DVB-T USB & FM" },
+	{ 0x1b80, 0xd3a4, "Twintech UT-40" },
+	{ 0x1b80, 0xd3a8, "ASUS U3100MINI_PLUS_V2" },
+	{ 0x1b80, 0xd3af, "SVEON STV27 DVB-T USB & FM" },
+	{ 0x1b80, 0xd3b0, "SVEON STV21 DVB-T USB & FM" },
+	{ 0x1d19, 0x1101, "Dexatek DK DVB-T Dongle (Logilink VG0002A)" },
+	{ 0x1d19, 0x1102, "Dexatek DK DVB-T Dongle (MSI DigiVox mini II V3.0)" },
+	{ 0x1d19, 0x1103, "Dexatek Technology Ltd. DK 5217 DVB-T Dongle" },
+	{ 0x1d19, 0x1104, "MSI DigiVox Micro HD" },
+	{ 0x1f4d, 0xa803, "Sweex DVB-T USB" },
+	{ 0x1f4d, 0xb803, "GTek T803" },
+	{ 0x1f4d, 0xc803, "Lifeview LV5TDeluxe" },
+	{ 0x1f4d, 0xd286, "MyGica TD312" },
+	{ 0x1f4d, 0xd803, "PROlectrix DV107669" },
+};
+
+#define DEFAULT_BUF_NUMBER	15
+#define DEFAULT_BUF_LENGTH	(16 * 32 * 512)
+
+#define DEF_RTL_XTAL_FREQ	28800000
+#define MIN_RTL_XTAL_FREQ	(DEF_RTL_XTAL_FREQ - 1000)
+#define MAX_RTL_XTAL_FREQ	(DEF_RTL_XTAL_FREQ + 1000)
+
+#define CTRL_IN		(LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_ENDPOINT_IN)
+#define CTRL_OUT	(LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_ENDPOINT_OUT)
+#define CTRL_TIMEOUT	300
+#define BULK_TIMEOUT	0
+
+#define EEPROM_ADDR	0xa0
+
+enum usb_reg {
+	USB_SYSCTL		= 0x2000,
+	USB_CTRL		= 0x2010,
+	USB_STAT		= 0x2014,
+	USB_EPA_CFG		= 0x2144,
+	USB_EPA_CTL		= 0x2148,
+	USB_EPA_MAXPKT		= 0x2158,
+	USB_EPA_MAXPKT_2	= 0x215a,
+	USB_EPA_FIFO_CFG	= 0x2160,
+};
+
+enum sys_reg {
+	DEMOD_CTL		= 0x3000,
+	GPO			= 0x3001,
+	GPI			= 0x3002,
+	GPOE			= 0x3003,
+	GPD			= 0x3004,
+	SYSINTE			= 0x3005,
+	SYSINTS			= 0x3006,
+	GP_CFG0			= 0x3007,
+	GP_CFG1			= 0x3008,
+	SYSINTE_1		= 0x3009,
+	SYSINTS_1		= 0x300a,
+	DEMOD_CTL_1		= 0x300b,
+	IR_SUSPEND		= 0x300c,
+};
+
+enum blocks {
+	DEMODB			= 0,
+	USBB			= 1,
+	SYSB			= 2,
+	TUNB			= 3,
+	ROMB			= 4,
+	IRB			= 5,
+	IICB			= 6,
+};
+
+int rtlsdr_read_array(rtlsdr_dev_t *dev, uint8_t block, uint16_t addr, uint8_t *array, uint8_t len)
+{
+	int r;
+	uint16_t index = (block << 8);
+
+	r = libusb_control_transfer(dev->devh, CTRL_IN, 0, addr, index, array, len, CTRL_TIMEOUT);
+#if 0
+	if (r < 0)
+		fprintf(stderr, "%s failed with %d\n", __FUNCTION__, r);
+#endif
+	return r;
+}
+
+int rtlsdr_write_array(rtlsdr_dev_t *dev, uint8_t block, uint16_t addr, uint8_t *array, uint8_t len)
+{
+	int r;
+	uint16_t index = (block << 8) | 0x10;
+
+	r = libusb_control_transfer(dev->devh, CTRL_OUT, 0, addr, index, array, len, CTRL_TIMEOUT);
+#if 0
+	if (r < 0)
+		fprintf(stderr, "%s failed with %d\n", __FUNCTION__, r);
+#endif
+	return r;
+}
+
+int rtlsdr_i2c_write_reg(rtlsdr_dev_t *dev, uint8_t i2c_addr, uint8_t reg, uint8_t val)
+{
+	uint16_t addr = i2c_addr;
+	uint8_t data[2];
+
+	data[0] = reg;
+	data[1] = val;
+	return rtlsdr_write_array(dev, IICB, addr, (uint8_t *)&data, 2);
+}
+
+uint8_t rtlsdr_i2c_read_reg(rtlsdr_dev_t *dev, uint8_t i2c_addr, uint8_t reg)
+{
+	uint16_t addr = i2c_addr;
+	uint8_t data = 0;
+
+	rtlsdr_write_array(dev, IICB, addr, &reg, 1);
+	rtlsdr_read_array(dev, IICB, addr, &data, 1);
+
+	return data;
+}
+
+int rtlsdr_i2c_write(rtlsdr_dev_t *dev, uint8_t i2c_addr, uint8_t *buffer, int len)
+{
+	uint16_t addr = i2c_addr;
+
+	if (!dev)
+		return -1;
+
+	return rtlsdr_write_array(dev, IICB, addr, buffer, len);
+}
+
+int rtlsdr_i2c_read(rtlsdr_dev_t *dev, uint8_t i2c_addr, uint8_t *buffer, int len)
+{
+	uint16_t addr = i2c_addr;
+
+	if (!dev)
+		return -1;
+
+	return rtlsdr_read_array(dev, IICB, addr, buffer, len);
+}
+
+uint16_t rtlsdr_read_reg(rtlsdr_dev_t *dev, uint8_t block, uint16_t addr, uint8_t len)
+{
+	int r;
+	unsigned char data[2];
+	uint16_t index = (block << 8);
+	uint16_t reg;
+
+	r = libusb_control_transfer(dev->devh, CTRL_IN, 0, addr, index, data, len, CTRL_TIMEOUT);
+
+	if (r < 0)
+		fprintf(stderr, "%s failed with %d\n", __FUNCTION__, r);
+
+	reg = (data[1] << 8) | data[0];
+
+	return reg;
+}
+
+int rtlsdr_write_reg(rtlsdr_dev_t *dev, uint8_t block, uint16_t addr, uint16_t val, uint8_t len)
+{
+	int r;
+	unsigned char data[2];
+
+	uint16_t index = (block << 8) | 0x10;
+
+	if (len == 1)
+		data[0] = val & 0xff;
+	else
+		data[0] = val >> 8;
+
+	data[1] = val & 0xff;
+
+	r = libusb_control_transfer(dev->devh, CTRL_OUT, 0, addr, index, data, len, CTRL_TIMEOUT);
+
+	if (r < 0)
+		fprintf(stderr, "%s failed with %d\n", __FUNCTION__, r);
+
+	return r;
+}
+
+uint16_t rtlsdr_demod_read_reg(rtlsdr_dev_t *dev, uint8_t page, uint16_t addr, uint8_t len)
+{
+	int r;
+	unsigned char data[2];
+
+	uint16_t index = page;
+	uint16_t reg;
+	addr = (addr << 8) | 0x20;
+
+	r = libusb_control_transfer(dev->devh, CTRL_IN, 0, addr, index, data, len, CTRL_TIMEOUT);
+
+	if (r < 0)
+		fprintf(stderr, "%s failed with %d\n", __FUNCTION__, r);
+
+	reg = (data[1] << 8) | data[0];
+
+	return reg;
+}
+
+int rtlsdr_demod_write_reg(rtlsdr_dev_t *dev, uint8_t page, uint16_t addr, uint16_t val, uint8_t len)
+{
+	int r;
+	unsigned char data[2];
+	uint16_t index = 0x10 | page;
+	addr = (addr << 8) | 0x20;
+
+	if (len == 1)
+		data[0] = val & 0xff;
+	else
+		data[0] = val >> 8;
+
+	data[1] = val & 0xff;
+
+	r = libusb_control_transfer(dev->devh, CTRL_OUT, 0, addr, index, data, len, CTRL_TIMEOUT);
+
+	if (r < 0)
+		fprintf(stderr, "%s failed with %d\n", __FUNCTION__, r);
+
+	rtlsdr_demod_read_reg(dev, 0x0a, 0x01, 1);
+
+	return (r == len) ? 0 : -1;
+}
+
+void rtlsdr_set_gpio_bit(rtlsdr_dev_t *dev, uint8_t gpio, int val)
+{
+	uint16_t r;
+
+	gpio = 1 << gpio;
+	r = rtlsdr_read_reg(dev, SYSB, GPO, 1);
+	r = val ? (r | gpio) : (r & ~gpio);
+	rtlsdr_write_reg(dev, SYSB, GPO, r, 1);
+}
+
+void rtlsdr_set_gpio_output(rtlsdr_dev_t *dev, uint8_t gpio)
+{
+	int r;
+	gpio = 1 << gpio;
+
+	r = rtlsdr_read_reg(dev, SYSB, GPD, 1);
+	rtlsdr_write_reg(dev, SYSB, GPD, r & ~gpio, 1);
+	r = rtlsdr_read_reg(dev, SYSB, GPOE, 1);
+	rtlsdr_write_reg(dev, SYSB, GPOE, r | gpio, 1);
+}
+
+void rtlsdr_set_i2c_repeater(rtlsdr_dev_t *dev, int on)
+{
+	rtlsdr_demod_write_reg(dev, 1, 0x01, on ? 0x18 : 0x10, 1);
+}
+
+int rtlsdr_set_fir(rtlsdr_dev_t *dev)
+{
+	uint8_t fir[20];
+
+	int i;
+	/* format: int8_t[8] */
+	for (i = 0; i < 8; ++i) {
+		const int val = dev->fir[i];
+		if (val < -128 || val > 127) {
+			return -1;
+		}
+		fir[i] = val;
+	}
+	/* format: int12_t[8] */
+	for (i = 0; i < 8; i += 2) {
+		const int val0 = dev->fir[8+i];
+		const int val1 = dev->fir[8+i+1];
+		if (val0 < -2048 || val0 > 2047 || val1 < -2048 || val1 > 2047) {
+			return -1;
+		}
+		fir[8+i*3/2] = val0 >> 4;
+		fir[8+i*3/2+1] = (val0 << 4) | ((val1 >> 8) & 0x0f);
+		fir[8+i*3/2+2] = val1;
+	}
+
+	for (i = 0; i < (int)sizeof(fir); i++) {
+		if (rtlsdr_demod_write_reg(dev, 1, 0x1c + i, fir[i], 1))
+				return -1;
+	}
+
+	return 0;
+}
+
+void rtlsdr_init_baseband(rtlsdr_dev_t *dev)
+{
+	unsigned int i;
+
+	/* initialize USB */
+	rtlsdr_write_reg(dev, USBB, USB_SYSCTL, 0x09, 1);
+	rtlsdr_write_reg(dev, USBB, USB_EPA_MAXPKT, 0x0002, 2);
+	rtlsdr_write_reg(dev, USBB, USB_EPA_CTL, 0x1002, 2);
+
+	/* poweron demod */
+	rtlsdr_write_reg(dev, SYSB, DEMOD_CTL_1, 0x22, 1);
+	rtlsdr_write_reg(dev, SYSB, DEMOD_CTL, 0xe8, 1);
+
+	/* reset demod (bit 3, soft_rst) */
+	rtlsdr_demod_write_reg(dev, 1, 0x01, 0x14, 1);
+	rtlsdr_demod_write_reg(dev, 1, 0x01, 0x10, 1);
+
+	/* disable spectrum inversion and adjacent channel rejection */
+	rtlsdr_demod_write_reg(dev, 1, 0x15, 0x00, 1);
+	rtlsdr_demod_write_reg(dev, 1, 0x16, 0x0000, 2);
+
+	/* clear both DDC shift and IF frequency registers  */
+	for (i = 0; i < 6; i++)
+		rtlsdr_demod_write_reg(dev, 1, 0x16 + i, 0x00, 1);
+
+	rtlsdr_set_fir(dev);
+
+	/* enable SDR mode, disable DAGC (bit 5) */
+	rtlsdr_demod_write_reg(dev, 0, 0x19, 0x05, 1);
+
+	/* init FSM state-holding register */
+	rtlsdr_demod_write_reg(dev, 1, 0x93, 0xf0, 1);
+	rtlsdr_demod_write_reg(dev, 1, 0x94, 0x0f, 1);
+
+	/* disable AGC (en_dagc, bit 0) (this seems to have no effect) */
+	rtlsdr_demod_write_reg(dev, 1, 0x11, 0x00, 1);
+
+	/* disable RF and IF AGC loop */
+	rtlsdr_demod_write_reg(dev, 1, 0x04, 0x00, 1);
+
+	/* disable PID filter (enable_PID = 0) */
+	rtlsdr_demod_write_reg(dev, 0, 0x61, 0x60, 1);
+
+	/* opt_adc_iq = 0, default ADC_I/ADC_Q datapath */
+	rtlsdr_demod_write_reg(dev, 0, 0x06, 0x80, 1);
+
+	/* Enable Zero-IF mode (en_bbin bit), DC cancellation (en_dc_est),
+	 * IQ estimation/compensation (en_iq_comp, en_iq_est) */
+	rtlsdr_demod_write_reg(dev, 1, 0xb1, 0x1b, 1);
+
+	/* disable 4.096 MHz clock output on pin TP_CK0 */
+	rtlsdr_demod_write_reg(dev, 0, 0x0d, 0x83, 1);
+}
+
+int rtlsdr_deinit_baseband(rtlsdr_dev_t *dev)
+{
+	int r = 0;
+
+	if (!dev)
+		return -1;
+
+	if (dev->tuner && dev->tuner->exit) {
+		rtlsdr_set_i2c_repeater(dev, 1);
+		r = dev->tuner->exit(dev); /* deinitialize tuner */
+		rtlsdr_set_i2c_repeater(dev, 0);
+	}
+
+	/* poweroff demodulator and ADCs */
+	rtlsdr_write_reg(dev, SYSB, DEMOD_CTL, 0x20, 1);
+
+	return r;
+}
+
+static int rtlsdr_set_if_freq(rtlsdr_dev_t *dev, uint32_t freq)
+{
+	uint32_t rtl_xtal;
+	int32_t if_freq;
+	uint8_t tmp;
+	int r;
+
+	if (!dev)
+		return -1;
+
+	/* read corrected clock value */
+	if (rtlsdr_get_xtal_freq(dev, &rtl_xtal, NULL))
+		return -2;
+
+	if_freq = ((freq * TWO_POW(22)) / rtl_xtal) * (-1);
+
+	tmp = (if_freq >> 16) & 0x3f;
+	r = rtlsdr_demod_write_reg(dev, 1, 0x19, tmp, 1);
+	tmp = (if_freq >> 8) & 0xff;
+	r |= rtlsdr_demod_write_reg(dev, 1, 0x1a, tmp, 1);
+	tmp = if_freq & 0xff;
+	r |= rtlsdr_demod_write_reg(dev, 1, 0x1b, tmp, 1);
+
+	return r;
+}
+
+int rtlsdr_set_sample_freq_correction(rtlsdr_dev_t *dev, int ppm)
+{
+	int r = 0;
+	uint8_t tmp;
+	int16_t offs = ppm * (-1) * TWO_POW(24) / 1000000;
+
+	tmp = offs & 0xff;
+	r |= rtlsdr_demod_write_reg(dev, 1, 0x3f, tmp, 1);
+	tmp = (offs >> 8) & 0x3f;
+	r |= rtlsdr_demod_write_reg(dev, 1, 0x3e, tmp, 1);
+
+	return r;
+}
+
+int rtlsdr_set_xtal_freq(rtlsdr_dev_t *dev, uint32_t rtl_freq, uint32_t tuner_freq)
+{
+	int r = 0;
+
+	if (!dev)
+		return -1;
+
+	if (rtl_freq > 0 &&
+		(rtl_freq < MIN_RTL_XTAL_FREQ || rtl_freq > MAX_RTL_XTAL_FREQ))
+		return -2;
+
+	if (rtl_freq > 0 && dev->rtl_xtal != rtl_freq) {
+		dev->rtl_xtal = rtl_freq;
+
+		/* update xtal-dependent settings */
+		if (dev->rate)
+			r = rtlsdr_set_sample_rate(dev, dev->rate);
+	}
+
+	if (dev->tun_xtal != tuner_freq) {
+		if (0 == tuner_freq)
+			dev->tun_xtal = dev->rtl_xtal;
+		else
+			dev->tun_xtal = tuner_freq;
+
+		/* read corrected clock value into e4k and r82xx structure */
+		if (rtlsdr_get_xtal_freq(dev, NULL, &dev->e4k_s.vco.fosc) ||
+		    rtlsdr_get_xtal_freq(dev, NULL, &dev->r82xx_c.xtal))
+			return -3;
+
+		/* update xtal-dependent settings */
+		if (dev->freq)
+			r = rtlsdr_set_center_freq(dev, dev->freq);
+	}
+
+	return r;
+}
+
+int rtlsdr_get_xtal_freq(rtlsdr_dev_t *dev, uint32_t *rtl_freq, uint32_t *tuner_freq)
+{
+	if (!dev)
+		return -1;
+
+	#define APPLY_PPM_CORR(val,ppm) (((val) * (1.0 + (ppm) / 1e6)))
+
+	if (rtl_freq)
+		*rtl_freq = (uint32_t) APPLY_PPM_CORR(dev->rtl_xtal, dev->corr);
+
+	if (tuner_freq)
+		*tuner_freq = (uint32_t) APPLY_PPM_CORR(dev->tun_xtal, dev->corr);
+
+	return 0;
+}
+
+int rtlsdr_get_usb_strings(rtlsdr_dev_t *dev, char *manufact, char *product,
+			    char *serial)
+{
+	struct libusb_device_descriptor dd;
+	libusb_device *device = NULL;
+	const int buf_max = 256;
+	int r = 0;
+
+	if (!dev || !dev->devh)
+		return -1;
+
+	device = libusb_get_device(dev->devh);
+
+	r = libusb_get_device_descriptor(device, &dd);
+	if (r < 0)
+		return -1;
+
+	if (manufact) {
+		memset(manufact, 0, buf_max);
+		libusb_get_string_descriptor_ascii(dev->devh, dd.iManufacturer,
+						   (unsigned char *)manufact,
+						   buf_max);
+	}
+
+	if (product) {
+		memset(product, 0, buf_max);
+		libusb_get_string_descriptor_ascii(dev->devh, dd.iProduct,
+						   (unsigned char *)product,
+						   buf_max);
+	}
+
+	if (serial) {
+		memset(serial, 0, buf_max);
+		libusb_get_string_descriptor_ascii(dev->devh, dd.iSerialNumber,
+						   (unsigned char *)serial,
+						   buf_max);
+	}
+
+	return 0;
+}
+
+int rtlsdr_write_eeprom(rtlsdr_dev_t *dev, uint8_t *data, uint8_t offset, uint16_t len)
+{
+	int r = 0;
+	int i;
+	uint8_t cmd[2];
+
+	if (!dev)
+		return -1;
+
+	if ((len + offset) > 256)
+		return -2;
+
+	for (i = 0; i < len; i++) {
+		cmd[0] = i + offset;
+		r = rtlsdr_write_array(dev, IICB, EEPROM_ADDR, cmd, 1);
+		r = rtlsdr_read_array(dev, IICB, EEPROM_ADDR, &cmd[1], 1);
+
+		/* only write the byte if it differs */
+		if (cmd[1] == data[i])
+			continue;
+
+		cmd[1] = data[i];
+		r = rtlsdr_write_array(dev, IICB, EEPROM_ADDR, cmd, 2);
+		if (r != sizeof(cmd))
+			return -3;
+
+		/* for some EEPROMs (e.g. ATC 240LC02) we need a delay
+		 * between write operations, otherwise they will fail */
+#ifdef _WIN32
+		Sleep(5);
+#else
+		usleep(5000);
+#endif
+	}
+
+	return 0;
+}
+
+int rtlsdr_read_eeprom(rtlsdr_dev_t *dev, uint8_t *data, uint8_t offset, uint16_t len)
+{
+	int r = 0;
+	int i;
+
+	if (!dev)
+		return -1;
+
+	if ((len + offset) > 256)
+		return -2;
+
+	r = rtlsdr_write_array(dev, IICB, EEPROM_ADDR, &offset, 1);
+	if (r < 0)
+		return -3;
+
+	for (i = 0; i < len; i++) {
+		r = rtlsdr_read_array(dev, IICB, EEPROM_ADDR, data + i, 1);
+
+		if (r < 0)
+			return -3;
+	}
+
+	return r;
+}
+
+int rtlsdr_set_center_freq(rtlsdr_dev_t *dev, uint32_t freq)
+{
+	int r = -1;
+
+	if (!dev || !dev->tuner)
+		return -1;
+
+	if (dev->direct_sampling) {
+		r = rtlsdr_set_if_freq(dev, freq);
+	} else if (dev->tuner && dev->tuner->set_freq) {
+		rtlsdr_set_i2c_repeater(dev, 1);
+		r = dev->tuner->set_freq(dev, freq - dev->offs_freq);
+		rtlsdr_set_i2c_repeater(dev, 0);
+	}
+
+	if (!r)
+		dev->freq = freq;
+	else
+		dev->freq = 0;
+
+	return r;
+}
+
+uint32_t rtlsdr_get_center_freq(rtlsdr_dev_t *dev)
+{
+	if (!dev)
+		return 0;
+
+	return dev->freq;
+}
+
+int rtlsdr_set_freq_correction(rtlsdr_dev_t *dev, int ppm)
+{
+	int r = 0;
+
+	if (!dev)
+		return -1;
+
+	if (dev->corr == ppm)
+		return -2;
+
+	dev->corr = ppm;
+
+	r |= rtlsdr_set_sample_freq_correction(dev, ppm);
+
+	/* read corrected clock value into e4k and r82xx structure */
+	if (rtlsdr_get_xtal_freq(dev, NULL, &dev->e4k_s.vco.fosc) ||
+	    rtlsdr_get_xtal_freq(dev, NULL, &dev->r82xx_c.xtal))
+		return -3;
+
+	if (dev->freq) /* retune to apply new correction value */
+		r |= rtlsdr_set_center_freq(dev, dev->freq);
+
+	return r;
+}
+
+int rtlsdr_get_freq_correction(rtlsdr_dev_t *dev)
+{
+	if (!dev)
+		return 0;
+
+	return dev->corr;
+}
+
+enum rtlsdr_tuner rtlsdr_get_tuner_type(rtlsdr_dev_t *dev)
+{
+	if (!dev)
+		return RTLSDR_TUNER_UNKNOWN;
+
+	return dev->tuner_type;
+}
+
+int rtlsdr_get_tuner_gains(rtlsdr_dev_t *dev, int *gains)
+{
+	/* all gain values are expressed in tenths of a dB */
+	const int e4k_gains[] = { -10, 15, 40, 65, 90, 115, 140, 165, 190, 215,
+				  240, 290, 340, 420 };
+	const int fc0012_gains[] = { -99, -40, 71, 179, 192 };
+	const int fc0013_gains[] = { -99, -73, -65, -63, -60, -58, -54, 58, 61,
+				       63, 65, 67, 68, 70, 71, 179, 181, 182,
+				       184, 186, 188, 191, 197 };
+	const int fc2580_gains[] = { 0 /* no gain values */ };
+	const int r82xx_gains[] = { 0, 9, 14, 27, 37, 77, 87, 125, 144, 157,
+				     166, 197, 207, 229, 254, 280, 297, 328,
+				     338, 364, 372, 386, 402, 421, 434, 439,
+				     445, 480, 496 };
+	const int unknown_gains[] = { 0 /* no gain values */ };
+
+	const int *ptr = NULL;
+	int len = 0;
+
+	if (!dev)
+		return -1;
+
+	switch (dev->tuner_type) {
+	case RTLSDR_TUNER_E4000:
+		ptr = e4k_gains; len = sizeof(e4k_gains);
+		break;
+	case RTLSDR_TUNER_FC0012:
+		ptr = fc0012_gains; len = sizeof(fc0012_gains);
+		break;
+	case RTLSDR_TUNER_FC0013:
+		ptr = fc0013_gains; len = sizeof(fc0013_gains);
+		break;
+	case RTLSDR_TUNER_FC2580:
+		ptr = fc2580_gains; len = sizeof(fc2580_gains);
+		break;
+	case RTLSDR_TUNER_R820T:
+	case RTLSDR_TUNER_R828D:
+		ptr = r82xx_gains; len = sizeof(r82xx_gains);
+		break;
+	default:
+		ptr = unknown_gains; len = sizeof(unknown_gains);
+		break;
+	}
+
+	if (!gains) { /* no buffer provided, just return the count */
+		return len / sizeof(int);
+	} else {
+		if (len)
+			memcpy(gains, ptr, len);
+
+		return len / sizeof(int);
+	}
+}
+
+int rtlsdr_set_tuner_bandwidth(rtlsdr_dev_t *dev, uint32_t bw)
+{
+	int r = 0;
+
+	if (!dev || !dev->tuner)
+		return -1;
+
+	if (dev->tuner->set_bw) {
+		rtlsdr_set_i2c_repeater(dev, 1);
+		r = dev->tuner->set_bw(dev, bw > 0 ? bw : dev->rate);
+		rtlsdr_set_i2c_repeater(dev, 0);
+		if (r)
+			return r;
+		dev->bw = bw;
+	}
+	return r;
+}
+
+int rtlsdr_set_tuner_gain(rtlsdr_dev_t *dev, int gain)
+{
+	int r = 0;
+
+	if (!dev || !dev->tuner)
+		return -1;
+
+	if (dev->tuner->set_gain) {
+		rtlsdr_set_i2c_repeater(dev, 1);
+		r = dev->tuner->set_gain((void *)dev, gain);
+		rtlsdr_set_i2c_repeater(dev, 0);
+	}
+
+	if (!r)
+		dev->gain = gain;
+	else
+		dev->gain = 0;
+
+	return r;
+}
+
+int rtlsdr_get_tuner_gain(rtlsdr_dev_t *dev)
+{
+	if (!dev)
+		return 0;
+
+	return dev->gain;
+}
+
+int rtlsdr_set_tuner_if_gain(rtlsdr_dev_t *dev, int stage, int gain)
+{
+	int r = 0;
+
+	if (!dev || !dev->tuner)
+		return -1;
+
+	if (dev->tuner->set_if_gain) {
+		rtlsdr_set_i2c_repeater(dev, 1);
+		r = dev->tuner->set_if_gain(dev, stage, gain);
+		rtlsdr_set_i2c_repeater(dev, 0);
+	}
+
+	return r;
+}
+
+int rtlsdr_set_tuner_gain_mode(rtlsdr_dev_t *dev, int mode)
+{
+	int r = 0;
+
+	if (!dev || !dev->tuner)
+		return -1;
+
+	if (dev->tuner->set_gain_mode) {
+		rtlsdr_set_i2c_repeater(dev, 1);
+		r = dev->tuner->set_gain_mode((void *)dev, mode);
+		rtlsdr_set_i2c_repeater(dev, 0);
+	}
+
+	return r;
+}
+
+int rtlsdr_set_sample_rate(rtlsdr_dev_t *dev, uint32_t samp_rate)
+{
+	int r = 0;
+	uint16_t tmp;
+	uint32_t rsamp_ratio, real_rsamp_ratio;
+	double real_rate;
+
+	if (!dev)
+		return -1;
+
+	/* check if the rate is supported by the resampler */
+	if ((samp_rate <= 225000) || (samp_rate > 3200000) ||
+	   ((samp_rate > 300000) && (samp_rate <= 900000))) {
+		fprintf(stderr, "Invalid sample rate: %u Hz\n", samp_rate);
+		return -EINVAL;
+	}
+
+	rsamp_ratio = (dev->rtl_xtal * TWO_POW(22)) / samp_rate;
+	rsamp_ratio &= 0x0ffffffc;
+
+	real_rsamp_ratio = rsamp_ratio | ((rsamp_ratio & 0x08000000) << 1);
+	real_rate = (dev->rtl_xtal * TWO_POW(22)) / real_rsamp_ratio;
+
+	if ( ((double)samp_rate) != real_rate )
+		fprintf(stderr, "Exact sample rate is: %f Hz\n", real_rate);
+
+	dev->rate = (uint32_t)real_rate;
+
+	if (dev->tuner && dev->tuner->set_bw) {
+		rtlsdr_set_i2c_repeater(dev, 1);
+		dev->tuner->set_bw(dev, dev->bw > 0 ? dev->bw : dev->rate);
+		rtlsdr_set_i2c_repeater(dev, 0);
+	}
+
+	tmp = (rsamp_ratio >> 16);
+	r |= rtlsdr_demod_write_reg(dev, 1, 0x9f, tmp, 2);
+	tmp = rsamp_ratio & 0xffff;
+	r |= rtlsdr_demod_write_reg(dev, 1, 0xa1, tmp, 2);
+
+	r |= rtlsdr_set_sample_freq_correction(dev, dev->corr);
+
+	/* reset demod (bit 3, soft_rst) */
+	r |= rtlsdr_demod_write_reg(dev, 1, 0x01, 0x14, 1);
+	r |= rtlsdr_demod_write_reg(dev, 1, 0x01, 0x10, 1);
+
+	/* recalculate offset frequency if offset tuning is enabled */
+	if (dev->offs_freq)
+		rtlsdr_set_offset_tuning(dev, 1);
+
+	return r;
+}
+
+uint32_t rtlsdr_get_sample_rate(rtlsdr_dev_t *dev)
+{
+	if (!dev)
+		return 0;
+
+	return dev->rate;
+}
+
+int rtlsdr_set_testmode(rtlsdr_dev_t *dev, int on)
+{
+	if (!dev)
+		return -1;
+
+	return rtlsdr_demod_write_reg(dev, 0, 0x19, on ? 0x03 : 0x05, 1);
+}
+
+int rtlsdr_set_agc_mode(rtlsdr_dev_t *dev, int on)
+{
+	if (!dev)
+		return -1;
+
+	return rtlsdr_demod_write_reg(dev, 0, 0x19, on ? 0x25 : 0x05, 1);
+}
+
+int rtlsdr_set_direct_sampling(rtlsdr_dev_t *dev, int on)
+{
+	int r = 0;
+
+	if (!dev)
+		return -1;
+
+	if (on) {
+		if (dev->tuner && dev->tuner->exit) {
+			rtlsdr_set_i2c_repeater(dev, 1);
+			r = dev->tuner->exit(dev);
+			rtlsdr_set_i2c_repeater(dev, 0);
+		}
+
+		/* disable Zero-IF mode */
+		r |= rtlsdr_demod_write_reg(dev, 1, 0xb1, 0x1a, 1);
+
+		/* disable spectrum inversion */
+		r |= rtlsdr_demod_write_reg(dev, 1, 0x15, 0x00, 1);
+
+		/* only enable In-phase ADC input */
+		r |= rtlsdr_demod_write_reg(dev, 0, 0x08, 0x4d, 1);
+
+		/* swap I and Q ADC, this allows to select between two inputs */
+		r |= rtlsdr_demod_write_reg(dev, 0, 0x06, (on > 1) ? 0x90 : 0x80, 1);
+
+		fprintf(stderr, "Enabled direct sampling mode, input %i\n", on);
+		dev->direct_sampling = on;
+	} else {
+		if (dev->tuner && dev->tuner->init) {
+			rtlsdr_set_i2c_repeater(dev, 1);
+			r |= dev->tuner->init(dev);
+			rtlsdr_set_i2c_repeater(dev, 0);
+		}
+
+		if ((dev->tuner_type == RTLSDR_TUNER_R820T) ||
+		    (dev->tuner_type == RTLSDR_TUNER_R828D)) {
+			r |= rtlsdr_set_if_freq(dev, R82XX_IF_FREQ);
+
+			/* enable spectrum inversion */
+			r |= rtlsdr_demod_write_reg(dev, 1, 0x15, 0x01, 1);
+		} else {
+			r |= rtlsdr_set_if_freq(dev, 0);
+
+			/* enable In-phase + Quadrature ADC input */
+			r |= rtlsdr_demod_write_reg(dev, 0, 0x08, 0xcd, 1);
+
+			/* Enable Zero-IF mode */
+			r |= rtlsdr_demod_write_reg(dev, 1, 0xb1, 0x1b, 1);
+		}
+
+		/* opt_adc_iq = 0, default ADC_I/ADC_Q datapath */
+		r |= rtlsdr_demod_write_reg(dev, 0, 0x06, 0x80, 1);
+
+		fprintf(stderr, "Disabled direct sampling mode\n");
+		dev->direct_sampling = 0;
+	}
+
+	r |= rtlsdr_set_center_freq(dev, dev->freq);
+
+	return r;
+}
+
+int rtlsdr_get_direct_sampling(rtlsdr_dev_t *dev)
+{
+	if (!dev)
+		return -1;
+
+	return dev->direct_sampling;
+}
+
+int rtlsdr_set_offset_tuning(rtlsdr_dev_t *dev, int on)
+{
+	int r = 0;
+	int bw;
+
+	if (!dev)
+		return -1;
+
+	if ((dev->tuner_type == RTLSDR_TUNER_R820T) ||
+	    (dev->tuner_type == RTLSDR_TUNER_R828D))
+		return -2;
+
+	if (dev->direct_sampling)
+		return -3;
+
+	/* based on keenerds 1/f noise measurements */
+	dev->offs_freq = on ? ((dev->rate / 2) * 170 / 100) : 0;
+	r |= rtlsdr_set_if_freq(dev, dev->offs_freq);
+
+	if (dev->tuner && dev->tuner->set_bw) {
+		rtlsdr_set_i2c_repeater(dev, 1);
+		if (on) {
+			bw = 2 * dev->offs_freq;
+		} else if (dev->bw > 0) {
+			bw = dev->bw;
+		} else {
+			bw = dev->rate;
+		}
+		dev->tuner->set_bw(dev, bw);
+		rtlsdr_set_i2c_repeater(dev, 0);
+	}
+
+	if (dev->freq > dev->offs_freq)
+		r |= rtlsdr_set_center_freq(dev, dev->freq);
+
+	return r;
+}
+
+int rtlsdr_get_offset_tuning(rtlsdr_dev_t *dev)
+{
+	if (!dev)
+		return -1;
+
+	return (dev->offs_freq) ? 1 : 0;
+}
+
+static rtlsdr_dongle_t *find_known_device(uint16_t vid, uint16_t pid)
+{
+	unsigned int i;
+	rtlsdr_dongle_t *device = NULL;
+
+	for (i = 0; i < sizeof(known_devices)/sizeof(rtlsdr_dongle_t); i++ ) {
+		if (known_devices[i].vid == vid && known_devices[i].pid == pid) {
+			device = &known_devices[i];
+			break;
+		}
+	}
+
+	return device;
+}
+
+uint32_t rtlsdr_get_device_count(void)
+{
+	int i,r;
+	libusb_context *ctx;
+	libusb_device **list;
+	uint32_t device_count = 0;
+	struct libusb_device_descriptor dd;
+	ssize_t cnt;
+
+	r = libusb_init(&ctx);
+	if(r < 0)
+		return 0;
+
+	cnt = libusb_get_device_list(ctx, &list);
+
+	for (i = 0; i < cnt; i++) {
+		libusb_get_device_descriptor(list[i], &dd);
+
+		if (find_known_device(dd.idVendor, dd.idProduct))
+			device_count++;
+	}
+
+	libusb_free_device_list(list, 1);
+
+	libusb_exit(ctx);
+
+	return device_count;
+}
+
+const char *rtlsdr_get_device_name(uint32_t index)
+{
+	int i,r;
+	libusb_context *ctx;
+	libusb_device **list;
+	struct libusb_device_descriptor dd;
+	rtlsdr_dongle_t *device = NULL;
+	uint32_t device_count = 0;
+	ssize_t cnt;
+
+	r = libusb_init(&ctx);
+	if(r < 0)
+		return "";
+
+	cnt = libusb_get_device_list(ctx, &list);
+
+	for (i = 0; i < cnt; i++) {
+		libusb_get_device_descriptor(list[i], &dd);
+
+		device = find_known_device(dd.idVendor, dd.idProduct);
+
+		if (device) {
+			device_count++;
+
+			if (index == device_count - 1)
+				break;
+		}
+	}
+
+	libusb_free_device_list(list, 1);
+
+	libusb_exit(ctx);
+
+	if (device)
+		return device->name;
+	else
+		return "";
+}
+
+int rtlsdr_get_device_usb_strings(uint32_t index, char *manufact,
+				   char *product, char *serial)
+{
+	int r = -2;
+	int i;
+	libusb_context *ctx;
+	libusb_device **list;
+	struct libusb_device_descriptor dd;
+	rtlsdr_dongle_t *device = NULL;
+	rtlsdr_dev_t devt;
+	uint32_t device_count = 0;
+	ssize_t cnt;
+
+	r = libusb_init(&ctx);
+	if(r < 0)
+		return r;
+
+	cnt = libusb_get_device_list(ctx, &list);
+
+	for (i = 0; i < cnt; i++) {
+		libusb_get_device_descriptor(list[i], &dd);
+
+		device = find_known_device(dd.idVendor, dd.idProduct);
+
+		if (device) {
+			device_count++;
+
+			if (index == device_count - 1) {
+				r = libusb_open(list[i], &devt.devh);
+				if (!r) {
+					r = rtlsdr_get_usb_strings(&devt,
+								   manufact,
+								   product,
+								   serial);
+					libusb_close(devt.devh);
+				}
+				break;
+			}
+		}
+	}
+
+	libusb_free_device_list(list, 1);
+
+	libusb_exit(ctx);
+
+	return r;
+}
+
+int rtlsdr_get_index_by_serial(const char *serial)
+{
+	int i, cnt, r;
+	char str[256];
+
+	if (!serial)
+		return -1;
+
+	cnt = rtlsdr_get_device_count();
+
+	if (!cnt)
+		return -2;
+
+	for (i = 0; i < cnt; i++) {
+		r = rtlsdr_get_device_usb_strings(i, NULL, NULL, str);
+		if (!r && !strcmp(serial, str))
+			return i;
+	}
+
+	return -3;
+}
+
+int rtlsdr_open(rtlsdr_dev_t **out_dev, uint32_t index)
+{
+	int r;
+	int i;
+	libusb_device **list;
+	rtlsdr_dev_t *dev = NULL;
+	libusb_device *device = NULL;
+	uint32_t device_count = 0;
+	struct libusb_device_descriptor dd;
+	uint8_t reg;
+	ssize_t cnt;
+
+	dev = malloc(sizeof(rtlsdr_dev_t));
+	if (NULL == dev)
+		return -ENOMEM;
+
+	memset(dev, 0, sizeof(rtlsdr_dev_t));
+	memcpy(dev->fir, fir_default, sizeof(fir_default));
+
+	r = libusb_init(&dev->ctx);
+	if(r < 0){
+		free(dev);
+		return -1;
+	}
+
+	dev->dev_lost = 1;
+
+	cnt = libusb_get_device_list(dev->ctx, &list);
+
+	for (i = 0; i < cnt; i++) {
+		device = list[i];
+
+		libusb_get_device_descriptor(list[i], &dd);
+
+		if (find_known_device(dd.idVendor, dd.idProduct)) {
+			device_count++;
+		}
+
+		if (index == device_count - 1)
+			break;
+
+		device = NULL;
+	}
+
+	if (!device) {
+		r = -1;
+		goto err;
+	}
+
+	r = libusb_open(device, &dev->devh);
+	if (r < 0) {
+		libusb_free_device_list(list, 1);
+		fprintf(stderr, "usb_open error %d\n", r);
+		if(r == LIBUSB_ERROR_ACCESS)
+			fprintf(stderr, "Please fix the device permissions, e.g. "
+			"by installing the udev rules file rtl-sdr.rules\n");
+		goto err;
+	}
+
+	libusb_free_device_list(list, 1);
+
+	if (libusb_kernel_driver_active(dev->devh, 0) == 1) {
+		dev->driver_active = 1;
+
+#ifdef DETACH_KERNEL_DRIVER
+		if (!libusb_detach_kernel_driver(dev->devh, 0)) {
+			fprintf(stderr, "Detached kernel driver\n");
+		} else {
+			fprintf(stderr, "Detaching kernel driver failed!");
+			goto err;
+		}
+#else
+		fprintf(stderr, "\nKernel driver is active, or device is "
+				"claimed by second instance of librtlsdr."
+				"\nIn the first case, please either detach"
+				" or blacklist the kernel module\n"
+				"(dvb_usb_rtl28xxu), or enable automatic"
+				" detaching at compile time.\n\n");
+#endif
+	}
+
+	r = libusb_claim_interface(dev->devh, 0);
+	if (r < 0) {
+		fprintf(stderr, "usb_claim_interface error %d\n", r);
+		goto err;
+	}
+
+	dev->rtl_xtal = DEF_RTL_XTAL_FREQ;
+
+	/* perform a dummy write, if it fails, reset the device */
+	if (rtlsdr_write_reg(dev, USBB, USB_SYSCTL, 0x09, 1) < 0) {
+		fprintf(stderr, "Resetting device...\n");
+		libusb_reset_device(dev->devh);
+	}
+
+	rtlsdr_init_baseband(dev);
+	dev->dev_lost = 0;
+
+	/* Probe tuners */
+	rtlsdr_set_i2c_repeater(dev, 1);
+
+	reg = rtlsdr_i2c_read_reg(dev, E4K_I2C_ADDR, E4K_CHECK_ADDR);
+	if (reg == E4K_CHECK_VAL) {
+		fprintf(stderr, "Found Elonics E4000 tuner\n");
+		dev->tuner_type = RTLSDR_TUNER_E4000;
+		goto found;
+	}
+
+	reg = rtlsdr_i2c_read_reg(dev, FC0013_I2C_ADDR, FC0013_CHECK_ADDR);
+	if (reg == FC0013_CHECK_VAL) {
+		fprintf(stderr, "Found Fitipower FC0013 tuner\n");
+		dev->tuner_type = RTLSDR_TUNER_FC0013;
+		goto found;
+	}
+
+	reg = rtlsdr_i2c_read_reg(dev, R820T_I2C_ADDR, R82XX_CHECK_ADDR);
+	if (reg == R82XX_CHECK_VAL) {
+		fprintf(stderr, "Found Rafael Micro R820T tuner\n");
+		dev->tuner_type = RTLSDR_TUNER_R820T;
+		goto found;
+	}
+
+	reg = rtlsdr_i2c_read_reg(dev, R828D_I2C_ADDR, R82XX_CHECK_ADDR);
+	if (reg == R82XX_CHECK_VAL) {
+		fprintf(stderr, "Found Rafael Micro R828D tuner\n");
+		dev->tuner_type = RTLSDR_TUNER_R828D;
+		goto found;
+	}
+
+	/* initialise GPIOs */
+	rtlsdr_set_gpio_output(dev, 4);
+
+	/* reset tuner before probing */
+	rtlsdr_set_gpio_bit(dev, 4, 1);
+	rtlsdr_set_gpio_bit(dev, 4, 0);
+
+	reg = rtlsdr_i2c_read_reg(dev, FC2580_I2C_ADDR, FC2580_CHECK_ADDR);
+	if ((reg & 0x7f) == FC2580_CHECK_VAL) {
+		fprintf(stderr, "Found FCI 2580 tuner\n");
+		dev->tuner_type = RTLSDR_TUNER_FC2580;
+		goto found;
+	}
+
+	reg = rtlsdr_i2c_read_reg(dev, FC0012_I2C_ADDR, FC0012_CHECK_ADDR);
+	if (reg == FC0012_CHECK_VAL) {
+		fprintf(stderr, "Found Fitipower FC0012 tuner\n");
+		rtlsdr_set_gpio_output(dev, 6);
+		dev->tuner_type = RTLSDR_TUNER_FC0012;
+		goto found;
+	}
+
+found:
+	/* use the rtl clock value by default */
+	dev->tun_xtal = dev->rtl_xtal;
+	dev->tuner = &tuners[dev->tuner_type];
+
+	switch (dev->tuner_type) {
+	case RTLSDR_TUNER_R828D:
+		dev->tun_xtal = R828D_XTAL_FREQ;
+		/* fall-through */
+	case RTLSDR_TUNER_R820T:
+		/* disable Zero-IF mode */
+		rtlsdr_demod_write_reg(dev, 1, 0xb1, 0x1a, 1);
+
+		/* only enable In-phase ADC input */
+		rtlsdr_demod_write_reg(dev, 0, 0x08, 0x4d, 1);
+
+		/* the R82XX use 3.57 MHz IF for the DVB-T 6 MHz mode, and
+		 * 4.57 MHz for the 8 MHz mode */
+		rtlsdr_set_if_freq(dev, R82XX_IF_FREQ);
+
+		/* enable spectrum inversion */
+		rtlsdr_demod_write_reg(dev, 1, 0x15, 0x01, 1);
+		break;
+	case RTLSDR_TUNER_UNKNOWN:
+		fprintf(stderr, "No supported tuner found\n");
+		rtlsdr_set_direct_sampling(dev, 1);
+		break;
+	default:
+		break;
+	}
+
+	if (dev->tuner->init)
+		r = dev->tuner->init(dev);
+
+	rtlsdr_set_i2c_repeater(dev, 0);
+
+	*out_dev = dev;
+
+	return 0;
+err:
+	if (dev) {
+		if (dev->devh)
+			libusb_close(dev->devh);
+
+		if (dev->ctx)
+			libusb_exit(dev->ctx);
+
+		free(dev);
+	}
+
+	return r;
+}
+
+int rtlsdr_close(rtlsdr_dev_t *dev)
+{
+	if (!dev)
+		return -1;
+
+	if(!dev->dev_lost) {
+		/* block until all async operations have been completed (if any) */
+		while (RTLSDR_INACTIVE != dev->async_status) {
+#ifdef _WIN32
+			Sleep(1);
+#else
+			usleep(1000);
+#endif
+		}
+
+		rtlsdr_deinit_baseband(dev);
+	}
+
+	libusb_release_interface(dev->devh, 0);
+
+#ifdef DETACH_KERNEL_DRIVER
+	if (dev->driver_active) {
+		if (!libusb_attach_kernel_driver(dev->devh, 0))
+			fprintf(stderr, "Reattached kernel driver\n");
+		else
+			fprintf(stderr, "Reattaching kernel driver failed!\n");
+	}
+#endif
+
+	libusb_close(dev->devh);
+
+	libusb_exit(dev->ctx);
+
+	free(dev);
+
+	return 0;
+}
+
+int rtlsdr_reset_buffer(rtlsdr_dev_t *dev)
+{
+	if (!dev)
+		return -1;
+
+	rtlsdr_write_reg(dev, USBB, USB_EPA_CTL, 0x1002, 2);
+	rtlsdr_write_reg(dev, USBB, USB_EPA_CTL, 0x0000, 2);
+
+	return 0;
+}
+
+int rtlsdr_read_sync(rtlsdr_dev_t *dev, void *buf, int len, int *n_read)
+{
+	if (!dev)
+		return -1;
+
+	return libusb_bulk_transfer(dev->devh, 0x81, buf, len, n_read, BULK_TIMEOUT);
+}
+
+static void LIBUSB_CALL _libusb_callback(struct libusb_transfer *xfer)
+{
+	rtlsdr_dev_t *dev = (rtlsdr_dev_t *)xfer->user_data;
+
+	if (LIBUSB_TRANSFER_COMPLETED == xfer->status) {
+		if (dev->cb)
+			dev->cb(xfer->buffer, xfer->actual_length, dev->cb_ctx);
+
+		libusb_submit_transfer(xfer); /* resubmit transfer */
+		dev->xfer_errors = 0;
+	} else if (LIBUSB_TRANSFER_CANCELLED != xfer->status) {
+#ifndef _WIN32
+		if (LIBUSB_TRANSFER_ERROR == xfer->status)
+			dev->xfer_errors++;
+
+		if (dev->xfer_errors >= dev->xfer_buf_num ||
+		    LIBUSB_TRANSFER_NO_DEVICE == xfer->status) {
+#endif
+			dev->dev_lost = 1;
+			rtlsdr_cancel_async(dev);
+			fprintf(stderr, "cb transfer status: %d, "
+				"canceling...\n", xfer->status);
+#ifndef _WIN32
+		}
+#endif
+	}
+}
+
+int rtlsdr_wait_async(rtlsdr_dev_t *dev, rtlsdr_read_async_cb_t cb, void *ctx)
+{
+	return rtlsdr_read_async(dev, cb, ctx, 0, 0);
+}
+
+static int _rtlsdr_alloc_async_buffers(rtlsdr_dev_t *dev)
+{
+	unsigned int i;
+
+	if (!dev)
+		return -1;
+
+	if (!dev->xfer) {
+		dev->xfer = malloc(dev->xfer_buf_num *
+				   sizeof(struct libusb_transfer *));
+
+		for(i = 0; i < dev->xfer_buf_num; ++i)
+			dev->xfer[i] = libusb_alloc_transfer(0);
+	}
+
+	if (dev->xfer_buf)
+		return -2;
+
+	dev->xfer_buf = malloc(dev->xfer_buf_num * sizeof(unsigned char *));
+	memset(dev->xfer_buf, 0, dev->xfer_buf_num * sizeof(unsigned char *));
+
+#if defined(ENABLE_ZEROCOPY) && defined (__linux__) && LIBUSB_API_VERSION >= 0x01000105
+	fprintf(stderr, "Allocating %d zero-copy buffers\n", dev->xfer_buf_num);
+
+	dev->use_zerocopy = 1;
+	for (i = 0; i < dev->xfer_buf_num; ++i) {
+		dev->xfer_buf[i] = libusb_dev_mem_alloc(dev->devh, dev->xfer_buf_len);
+
+		if (dev->xfer_buf[i]) {
+			/* Check if Kernel usbfs mmap() bug is present: if the
+			 * mapping is correct, the buffers point to memory that
+			 * was memset to 0 by the Kernel, otherwise, they point
+			 * to random memory. We check if the buffers are zeroed
+			 * and otherwise fall back to buffers in userspace.
+			 */
+			if (dev->xfer_buf[i][0] || memcmp(dev->xfer_buf[i],
+							  dev->xfer_buf[i] + 1,
+							  dev->xfer_buf_len - 1)) {
+				fprintf(stderr, "Detected Kernel usbfs mmap() "
+						"bug, falling back to buffers "
+						"in userspace\n");
+				dev->use_zerocopy = 0;
+				break;
+			}
+		} else {
+			fprintf(stderr, "Failed to allocate zero-copy "
+					"buffer for transfer %d\nFalling "
+					"back to buffers in userspace\n", i);
+			dev->use_zerocopy = 0;
+			break;
+		}
+	}
+
+	/* zero-copy buffer allocation failed (partially or completely)
+	 * we need to free the buffers again if already allocated */
+	if (!dev->use_zerocopy) {
+		for (i = 0; i < dev->xfer_buf_num; ++i) {
+			if (dev->xfer_buf[i])
+				libusb_dev_mem_free(dev->devh,
+						    dev->xfer_buf[i],
+						    dev->xfer_buf_len);
+		}
+	}
+#endif
+
+	/* no zero-copy available, allocate buffers in userspace */
+	if (!dev->use_zerocopy) {
+		for (i = 0; i < dev->xfer_buf_num; ++i) {
+			dev->xfer_buf[i] = malloc(dev->xfer_buf_len);
+
+			if (!dev->xfer_buf[i])
+				return -ENOMEM;
+		}
+	}
+
+	return 0;
+}
+
+static int _rtlsdr_free_async_buffers(rtlsdr_dev_t *dev)
+{
+	unsigned int i;
+
+	if (!dev)
+		return -1;
+
+	if (dev->xfer) {
+		for(i = 0; i < dev->xfer_buf_num; ++i) {
+			if (dev->xfer[i]) {
+				libusb_free_transfer(dev->xfer[i]);
+			}
+		}
+
+		free(dev->xfer);
+		dev->xfer = NULL;
+	}
+
+	if (dev->xfer_buf) {
+		for (i = 0; i < dev->xfer_buf_num; ++i) {
+			if (dev->xfer_buf[i]) {
+				if (dev->use_zerocopy) {
+#if defined (__linux__) && LIBUSB_API_VERSION >= 0x01000105
+					libusb_dev_mem_free(dev->devh,
+							    dev->xfer_buf[i],
+							    dev->xfer_buf_len);
+#endif
+				} else {
+					free(dev->xfer_buf[i]);
+				}
+			}
+		}
+
+		free(dev->xfer_buf);
+		dev->xfer_buf = NULL;
+	}
+
+	return 0;
+}
+
+int rtlsdr_read_async(rtlsdr_dev_t *dev, rtlsdr_read_async_cb_t cb, void *ctx,
+			  uint32_t buf_num, uint32_t buf_len)
+{
+	unsigned int i;
+	int r = 0;
+	struct timeval tv = { 1, 0 };
+	struct timeval zerotv = { 0, 0 };
+	enum rtlsdr_async_status next_status = RTLSDR_INACTIVE;
+
+	if (!dev)
+		return -1;
+
+	if (RTLSDR_INACTIVE != dev->async_status)
+		return -2;
+
+	dev->async_status = RTLSDR_RUNNING;
+	dev->async_cancel = 0;
+
+	dev->cb = cb;
+	dev->cb_ctx = ctx;
+
+	if (buf_num > 0)
+		dev->xfer_buf_num = buf_num;
+	else
+		dev->xfer_buf_num = DEFAULT_BUF_NUMBER;
+
+	if (buf_len > 0 && buf_len % 512 == 0) /* len must be multiple of 512 */
+		dev->xfer_buf_len = buf_len;
+	else
+		dev->xfer_buf_len = DEFAULT_BUF_LENGTH;
+
+	_rtlsdr_alloc_async_buffers(dev);
+
+	for(i = 0; i < dev->xfer_buf_num; ++i) {
+		libusb_fill_bulk_transfer(dev->xfer[i],
+					  dev->devh,
+					  0x81,
+					  dev->xfer_buf[i],
+					  dev->xfer_buf_len,
+					  _libusb_callback,
+					  (void *)dev,
+					  BULK_TIMEOUT);
+
+		r = libusb_submit_transfer(dev->xfer[i]);
+		if (r < 0) {
+			fprintf(stderr, "Failed to submit transfer %i\n"
+					"Please increase your allowed " 
+					"usbfs buffer size with the "
+					"following command:\n"
+					"echo 0 > /sys/module/usbcore"
+					"/parameters/usbfs_memory_mb\n", i);
+			dev->async_status = RTLSDR_CANCELING;
+			break;
+		}
+	}
+
+	while (RTLSDR_INACTIVE != dev->async_status) {
+		r = libusb_handle_events_timeout_completed(dev->ctx, &tv,
+							   &dev->async_cancel);
+		if (r < 0) {
+			/*fprintf(stderr, "handle_events returned: %d\n", r);*/
+			if (r == LIBUSB_ERROR_INTERRUPTED) /* stray signal */
+				continue;
+			break;
+		}
+
+		if (RTLSDR_CANCELING == dev->async_status) {
+			next_status = RTLSDR_INACTIVE;
+
+			if (!dev->xfer)
+				break;
+
+			for(i = 0; i < dev->xfer_buf_num; ++i) {
+				if (!dev->xfer[i])
+					continue;
+
+				if (LIBUSB_TRANSFER_CANCELLED !=
+						dev->xfer[i]->status) {
+					r = libusb_cancel_transfer(dev->xfer[i]);
+					/* handle events after canceling
+					 * to allow transfer status to
+					 * propagate */
+#ifdef _WIN32
+					Sleep(1);
+#endif
+					libusb_handle_events_timeout_completed(dev->ctx,
+									       &zerotv, NULL);
+					if (r < 0)
+						continue;
+
+					next_status = RTLSDR_CANCELING;
+				}
+			}
+
+			if (dev->dev_lost || RTLSDR_INACTIVE == next_status) {
+				/* handle any events that still need to
+				 * be handled before exiting after we
+				 * just cancelled all transfers */
+				libusb_handle_events_timeout_completed(dev->ctx,
+								       &zerotv, NULL);
+				break;
+			}
+		}
+	}
+
+	_rtlsdr_free_async_buffers(dev);
+
+	dev->async_status = next_status;
+
+	return r;
+}
+
+int rtlsdr_cancel_async(rtlsdr_dev_t *dev)
+{
+	if (!dev)
+		return -1;
+
+	/* if streaming, try to cancel gracefully */
+	if (RTLSDR_RUNNING == dev->async_status) {
+		dev->async_status = RTLSDR_CANCELING;
+		dev->async_cancel = 1;
+		return 0;
+	}
+
+	/* if called while in pending state, change the state forcefully */
+#if 0
+	if (RTLSDR_INACTIVE != dev->async_status) {
+		dev->async_status = RTLSDR_INACTIVE;
+		return 0;
+	}
+#endif
+	return -2;
+}
+
+uint32_t rtlsdr_get_tuner_clock(void *dev)
+{
+	uint32_t tuner_freq;
+
+	if (!dev)
+		return 0;
+
+	/* read corrected clock value */
+	if (rtlsdr_get_xtal_freq((rtlsdr_dev_t *)dev, NULL, &tuner_freq))
+		return 0;
+
+	return tuner_freq;
+}
+
+int rtlsdr_i2c_write_fn(void *dev, uint8_t addr, uint8_t *buf, int len)
+{
+	if (dev)
+		return rtlsdr_i2c_write(((rtlsdr_dev_t *)dev), addr, buf, len);
+
+	return -1;
+}
+
+int rtlsdr_i2c_read_fn(void *dev, uint8_t addr, uint8_t *buf, int len)
+{
+	if (dev)
+		return rtlsdr_i2c_read(((rtlsdr_dev_t *)dev), addr, buf, len);
+
+	return -1;
+}
+
+int rtlsdr_set_bias_tee_gpio(rtlsdr_dev_t *dev, int gpio, int on)
+{
+	if (!dev)
+		return -1;
+
+	rtlsdr_set_gpio_output(dev, gpio);
+	rtlsdr_set_gpio_bit(dev, gpio, on);
+
+	return 0;
+}
+
+int rtlsdr_set_bias_tee(rtlsdr_dev_t *dev, int on)
+{
+	return rtlsdr_set_bias_tee_gpio(dev, 0, on);
+}