sdrangel/plugins/samplesource/bladerf1input

BladeRF classic (v1) input plugin

Introduction

This input sample source plugin gets its samples from a BladeRF1 device using LibbladeRF v.2. This is available in Linux distributions only.

Build

The plugin will be built only if the BladeRF host library is installed in your system. If you build it from source and install it in a custom location say: /opt/install/libbladeRF you will have to add -DBLADERF_INCLUDE_DIR=/opt/install/libbladeRF to the cmake command line.

Note that libbladeRF v2 with git tag 2018.08 should be used (official release). The FPGA image v0.7.3 should be used accordingly. The FPGA .rbf file should be copied to the folder where the sdrangel binary resides. You can download FPGA images from here

The BladeRF Host library is also provided by many Linux distributions (check its version) and is built in the SDRangel binary releases.

Interface

1: Common stream parameters

1.1: Frequency

This is the center frequency of reception in kHz.

1.2: Start/Stop

Device start / stop button.

• Blue triangle icon: device is ready and can be started
• Green square icon: device is running and can be stopped
• Magenta (or pink) square icon: an error occurred. In the case the device was accidentally disconnected you may click on the icon, plug back in and start again.

1.3: Record

Record baseband I/Q stream toggle button

1.4: Stream sample rate

In device to host sample rate input mode (4A) this is the baseband I/Q sample rate in kS/s. This is the device to host sample rate (4) divided by the decimation factor (5).

In baseband sample rate input mode (4A) this is the device to host sample rate in kS/s. This is the baseband sample rate (4) multiplied by the decimation factor (5)

2: Auto correction options

These buttons control the local DSP auto correction options:

• DC: auto remove DC component
• IQ: auto make I/Q balance. The DC correction must be enabled for this to be effective.

3: XB-200 add-on control

This controls the optional XB-200 add-on when it is fitted to the BladeRF main board. These controls have no effect if the XB-200 board is absent. Options are:

• None: XB-200 is ignored
• Bypass: XB-200 is passed through
• Auto 1dB: The 50, 144 and 220 MHz filters are switched on automatically according to the frequency of reception when it is within the -1 dB passband of the filters
• Auto 3dB: The 50, 144 and 220 MHz filters are switched on automatically according to the frequency of reception when it is within the -3 dB passband of the filters
• Custom: The signal is routed through a custom filter
• 50M: The signal is routed through the 50 MHz filter
• 144M: The signal is routed through the 144 MHz filter
• 222M: The signal is routed through the 222 MHz filter

4A: Device sample rate / Baseband sample rate input toggle

Use this toggle button to switch the sample rate input next (4) between device sample rate and baseband sample rate input. The button shows the current mode:

• SR: device sample rate input mode. The baseband sample rate (1.4) is the device sample rate (4) divided by the decimation factor (5).
• BB: baseband sample rate input mode. The device sample rate (1.4) is the baseband sample rate (4) multiplied by the decimation factor (5).

4: Sample rate

This is the BladeRF device ADC sample rate or baseband sample rate in samples per second (S/s). The control (4A) is used to switch between the two input modes.

The limits are adjusted automatically. In baseband input mode the limits are driven by the decimation factor (5). You may need to increase this decimation factor to be able to reach lower values.

Use the wheels to adjust the sample rate. Left click on a digit sets the cursor position at this digit. Right click on a digit sets all digits on the right to zero. This effectively floors value at the digit position. Wheels are moved with the mousewheel while pointing at the wheel or by selecting the wheel with the left mouse click and using the keyboard arrows. Pressing shift simultaneously moves digit by 5 and pressing control moves it by 2.

5: Decimation factor

The I/Q stream from the BladeRF ADC is downsampled by a power of two before being sent to the baseband. Possible values are increasing powers of two: 1 (no decimation), 2, 4, 8, 16, 32, 64.

6: Baseband center frequency position relative the the BladeRF Rx center frequency

Possible values are:

• Cen: the decimation operation takes place around the BladeRF Rx center frequency Fs
• Inf: the decimation operation takes place around Fs - Fc.
• Sup: the decimation operation takes place around Fs + Fc.

With SR as the sample rate before decimation Fc is calculated as:

• if decimation n is 4 or lower: Fc = SR/2^(log2(n)-1). The device center frequency is on the side of the baseband. You need a RF filter bandwidth at least twice the baseband.
• if decimation n is 8 or higher: Fc = SR/n. The device center frequency is half the baseband away from the side of the baseband. You need a RF filter bandwidth at least 3 times the baseband.

7: Rx filter bandwidth

This is the Rx filter bandwidth in kHz in the LMS6002D device. Possible values are: 1500, 1750, 2500, 2750, 3000, 3840, 5000, 5500, 6000, 7000, 8750, 10000, 12000, 14000, 20000, 28000 kHz.

8: LNA gain

This is the LNA gain in dB. LNA is inside the LMS6002D chip and is placed before the RF mixer. Possible values are:

• 0dB: no gain
• 3dB
• 6dB

9: Variable gain amplifier #1 gain

The VGA1 gain can be adjusted from 5 dB to 30 dB in 1 dB steps. The VGA1 is inside the LMS6002D chip and is placed between the RF mixer and the baseband filter.

10: Variable gain amplifier #2 gain

The VGA2 gain can be adjusted from 0 dB to 30 dB in 3 dB steps. The VGA2 is inside the LMS6002D chip and is placed between the baseband filter and the ADC.