A modern Node.js wrapper around the librtlsdr library
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README.md

rtl-sdr

A low level binding to the librtlsdr library for Node.js.

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Prerequisites

This module requires that you have librtlsdr installed on your system. In turn librtlsdr requires libusb.

You can install librtlsdr with most package managers which will ensure you have the right dependencies.

Homebrew (macOS):

brew install librtlsdr

Debian based Linux distros:

apt-get install librtlsdr-dev

Installation

npm install rtl-sdr --save

Usage

const rtlsdr = require('rtl-sdr')

// Get number of connected RTLSDR devices
const deviceCount = rtlsdr.get_device_count()

if (!deviceCount) {
  console.log('No supported RTLSDR devices found')
  process.exit(1)
}

console.log('Found %d device(s):', deviceCount)

For a complete running example, see example.js.

API

The API is thin wrapper on top of the librltsdr API as found in the rtl-sdr.h file. All functions exposed by this module are named the same as their librtlsdr counterparts, except for the rtlsdr_ prefix.

Only a few changes have been made to the return values and function arguments in order to make this suitable for JavaScript.

Tuner Constants

The following constants are exposed on the rtlsdr object:

  • TUNER_UNKNOWN
  • TUNER_E4000
  • TUNER_FC0012
  • TUNER_FC0013
  • TUNER_FC2580
  • TUNER_R820T
  • TUNER_R828D

Functions

count = get_device_count()

Return number of devices found.

name = get_device_name(index)

Return name of device at index

error = get_device_usb_strings(index, manufact, product, serial)

Get manufacturer, product and serial number from device at index.

Arguments:

  • index - Device index
  • manufact - An zero filled Buffer with space for up to 256 bytes to which the manufacturer name will be written (may be null)
  • product - An zero filled Buffer with space for up to 256 bytes to which the product name will be written (may be null)
  • serial - An zero filled Buffer with space for up to 256 bytes to which the serial number will be written (may be null)

Returns 0 on success.

error = get_index_by_serial(serial)

Get device index by USB serial string descriptor.

Returns 0 on success, -1 if name is null, -2 if no devices were found at all, and -3 if devices were found, but nonee with mathcing name.

device = open(index)

Open device at index.

Returns a device handle that can be used as an argument to other functions.

error = close(device)

Close device.

Arguments:

  • device - The device handle given by open()

Returns 0 on success.

error = set_xtal_freq(device, rtl_freq, tuner_freq)

Set crystal oscillator frequencies used for the RTL2832 and the tuner IC.

Usually both ICs use the same clock. Changing the clock may make sense if you are applying an external clock to the tuner or to compensate the frequency (and samplerate) error caused by the original (cheap) crystal.

NOTE: Call this function only if you fully understand the implications.

Arguments:

  • device - The device handle given by open()
  • rtl_freq - Frequency value used to clock the RTL2832 in Hz
  • tuner_freq - Frequency value used to clock the tuner IC in Hz

Returns 0 on success.

error = get_xtal_freq(device, rtl_freq, tuner_freq)

Get crystal oscillator frequencies used for the RTL2832 and the tuner IC.

Usually both ICs use the same clock.

Arguments:

  • device - The device handle given by open()
  • rtl_freq - A 32 bit Buffer object to which a 32 bit unsigned integer will be written with the frequency value used to clock the RTL2832 in Hz
  • tuner_freq - A 32 bit Buffer object to which a 32 bit unsigned integer will be written with the frequency value used to clock the tuner IC in Hz

Returns 0 on success.

error = get_usb_strings(device, manufact, product, serial)

Get USB device strings.

NOTE: The string arguments must provide space for up to 256 bytes.

Arguments:

  • device - The device handle given by open()
  • manufact - An zero filled Buffer with space for up to 256 bytes to which the manufacturer name will be written (may be null)
  • product - An zero filled Buffer with space for up to 256 bytes to which the product name will be written (may be null)
  • serial - An zero filled Buffer with space for up to 256 bytes to which the serial number will be written (may be null)

Returns 0 on success

error = write_eeprom(device, data, offset, len)

Write the device EEPROM.

Arguments:

  • device - The device handle given by open()
  • data - Buffer of data to be written
  • offset - Address where the data should be written
  • len - Length of the data

Returns 0 on success, -1 if device handle is invalid, -2 if EEPROM size is exceeded, or -3 if no EEPROM was found.

error = read_eeprom(device, data, offset, len)

Read the device EEPROM.

Arguments:

  • device - The device handle given by open()
  • data - Buffer where the data should be written
  • offset - Address where the data should be read from
  • len - Length of the data

Returns 0 on success, -1 if device handle is invalid, -2 if EEPROM size is exceeded, or -3 if no EEPROM was found.

error = set_center_freq(device, freq)

Tune device to the given frequency.

Arguments:

  • freq - The center frequency to tune to

Returns 0 on success.

freq = get_center_freq(device)

Get actual frequency the device is tuned to.

Arguments:

  • device - The device handle given by open()

Returns 0 on error, frequency in Hz otherwise.

error = set_freq_correction(device, ppm)

Set the frequency correction value for the device.

Arguments:

  • device - The device handle given by open()
  • ppm - Correction value in parts per million (ppm)

Returns 0 on success.

ppm = get_freq_correction(device)

Get actual frequency correction value of the device.

Arguments:

  • device - The device handle given by open()

Returns correction value in parts per million (ppm).

type = get_tuner_type(device)

Get the tuner type.

Arguments:

  • device - The device handle given by open()

Returns TUNER_UNKNOWN on error, tuner type otherwise (see list of tuner constants above).

numGains = get_tuner_gains(device, gains)

Get a list of gains supported by the tuner.

NOTE: The gains argument must be preallocated by the caller. If null is being given instead, the number of available gain values will be returned.

Arguments:

  • device - The device handle given by open()
  • gains - Empty array provided by the caller to which the list of gain values will be written. In tenths of a dB, 115 means 11.5 dB. If using a TypedArray, use an Int32Array with enough room to fill in the available gains, e.g. size 100.

Returns <= 0 on error, number of available (returned) gain values otherwise.

error = set_tuner_gain(device, gain)

Set the gain for the device.

Manual gain mode must be enabled for this to work.

Valid gain values (in tenths of a dB) for the E4000 tuner: -10, 15, 40, 65, 90, 115, 140, 165, 190, 215, 240, 290, 340, 420, 430, 450, 470, 490.

Valid gain values may be queried with get_tuner_gains function.

Arguments:

  • device - The device handle given by open()
  • gain - In tenths of a dB, 115 means 11.5 dB

Returns 0 on success.

gain = get_tuner_gain(device)

Get actual gain the device is configured to.

Arguments:

  • device - The device handle given by open()

Returns 0 on error, otherwise gain in tenths of a dB, 115 means 11.5 dB.

error = set_tuner_if_gain(device, stage, gain)

Set the intermediate frequency gain for the device.

Arguments:

  • device - The device handle given by open()
  • stage - Intermediate frequency gain stage number (1 to 6 for E4000)
  • gain - In tenths of a dB, -30 means -3.0 dB

Returns 0 on success.

error = set_tuner_gain_mode(device, stage, gain)

Set the gain mode (automatic/manual) for the device. Manual gain mode must be enabled for the gain setter function to work.

Arguments:

  • device - The device handle given by open()
  • manual - Gain mode, 1 means manual gain mode shall be enabled.

Returns 0 on success.

error = set_sample_rate(device, samp_rate)

Set the sample rate for the device, also selects the baseband filters according to the requested sample rate for tuners where this is possible.

Arguments:

  • device - The device handle given by open()
  • samp_rate - The sample rate to be set, possible values are: 225001 - 300000 Hz and 900001 - 3200000 Hz. Sample loss is to be expected for rates > 2400000

Returns 0 on success, -EINVAL on invalid rate

hz = get_sample_rate(device)

Get actual sample rate the device is configured to.

Arguments:

  • device - The device handle given by open()

Returns 0 on error, sample rate in Hz otherwise.

error = set_testmode(device, test)

Enable test mode that returns an 8 bit counter instead of the samples. The counter is generated inside the RTL2832.

Arguments:

  • device - The device handle given by open()
  • test - Mode, 1 means enabled, 0 disabled

Returns 0 on success.

error = set_agc_mode(device, digital)

Enable or disable the internal digital AGC of the RTL2832.

Arguments:

  • device - The device handle given by open()
  • digital - AGC mode, 1 means enabled, 0 disabled

Returns 0 on success.

error = set_direct_sampling(device, on)

Enable or disable the direct sampling mode. When enabled, the IF mode of the RTL2832 is activated, and set_center_freq() will control the IF-frequency of the DDC, which can be used to tune from 0 to 28.8 MHz (xtal frequency of the RTL2832).

Arguments:

  • device - The device handle given by open()
  • on - 0 means disabled, 1 I-ADC input enabled, 2 Q-ADC input enabled

Returns 0 on success.

state = get_direct_sampling(device)

Get state of the direct sampling mode

Arguments:

  • device - The device handle given by open()

Returns -1 on error, 0 means disabled, 1 I-ADC input enabled, 2 Q-ADC input enabled.

error = set_offset_tuning(device, on)

Enable or disable offset tuning for zero-IF tuners, which allows to avoid problems caused by the DC offset of the ADCs and 1/f noise.

Arguments:

  • device - The device handle given by open()
  • on - 0 means disabled, 1 enabled

Returns 0 on success.

state = get_offset_tuning(device)

Get state of the offset tuning mode.

Arguments:

  • device - The device handle given by open()

Returns -1 on error, 0 means disabled, 1 enabled

error = reset_buffer(device)

Reset the internal buffer.

Arguments:

  • device - The device handle given by open()

Returns 0 on success.

error = read_sync(device, buf, len, n_read)

Read samples from the device synchronously.

NOTE: Make sure the buffer is big enough.

Arguments:

  • device - The device handle given by open()
  • buf - The buffer to read into
  • len - The size of the buffer
  • n_read - A Buffer.alloc(4) object to which a 32 bit integer will be written containing the size of the data that have been written to buf

Returns 0 on success.

read_async(device, on_data, on_end, buf_num, buf_len)

Read samples from the device asynchronously. Data will be read until it is being canceled using cancel_async()

Arguments:

  • device - The device handle given by open()
  • on_data - Callback function to return received samples. The callback will be called with a buffer as the first arguemnt and the size of the buffer as the second
  • on_end - Callback function to be called once no more samples will be read
  • buf_num - Optional buffer count, buf_num * buf_len = overall buffer size set to 0 for default buffer count (15)
  • buf_len - Optional buffer length, must be multiple of 512, should be a multiple of 16384 (URB size), set to 0 for default buffer length (16 * 32 * 512)

Returns 0 on success.

error = cancel_async(device)

Cancel all pending asynchronous operations on the device.

Arguments:

  • device - The device handle given by open()

Returns 0 on success.

License

MIT