RX Gain not set properly

[lopz77]

I'm having difficulties with the bladeRF lib, regarding configuring the gain of the rx channels.
Based on the code below, is there a specific order to perform the configuration? I noticed that the gain is only applied correctly when the channels are active.
Is there a correct order for config calls?

Code: Select all

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <libbladeRF.h>

#define FREQUENCY 2700000000 // 2_700_000_000
#define SAMPLERATE 2000000   // 1_000_000
#define BANDWIDTH 1000000    // 1_000_000
#define GAIN 30

int main()
{
    struct bladerf_metadata meta;
    struct bladerf *dev;
    int16_t *samples;

    unsigned int block_size = 2048;

    bladerf_sample_rate samplerate_actual;
    bladerf_frequency frequency_actual;
    bladerf_gain gain_actual;
    bladerf_bandwidth bandwidth_actual;

    int n_channels = 2; // 1 or 2 for BladeRF micro

    bladerf_channel_layout channel_layout = n_channels == 2 ? BLADERF_RX_X2 : BLADERF_RX_X1;
    unsigned int read_size = block_size / n_channels; // have to halve if using 2 channels?

    // allocate memory
    memset(&meta, 0, sizeof(meta));
    meta.flags = BLADERF_META_FLAG_RX_NOW;

    // samples = (int16_t *)calloc(block_size, 2 * sizeof(samples[0]));
    samples = malloc(block_size * 2 * sizeof(int16_t));

    if (samples == NULL)
        return -1;

    memset(samples, 0xFF, block_size * 2 * sizeof(int16_t));

    // open BladeRF
    if (bladerf_open(&dev, "*:serial=a8cf") != 0)
        return -1;

    if (bladerf_is_fpga_configured(dev) <= 0)
        return -1;

    // setup BladeRF, these specify a "bladerf_channel"
    for (int ch = 0; ch < n_channels; ch++)
    {
        if (bladerf_set_frequency(dev, BLADERF_CHANNEL_RX(ch), FREQUENCY) != 0)
            return -1;

        if (bladerf_get_frequency(dev, BLADERF_CHANNEL_RX(ch), &frequency_actual) != 0)
            return -1;

        if (bladerf_set_sample_rate(dev, BLADERF_CHANNEL_RX(ch), SAMPLERATE, &samplerate_actual) != 0)
            return -1;

        if (bladerf_get_sample_rate(dev, BLADERF_CHANNEL_RX(ch), &samplerate_actual) != 0)
            return -1;

        if (bladerf_set_gain_mode(dev, BLADERF_CHANNEL_RX(ch), BLADERF_GAIN_MGC) != 0)
            return -1;

        if (bladerf_set_gain(dev, BLADERF_CHANNEL_RX(ch), GAIN) != 0)
            return -1;

        if (bladerf_get_gain(dev, BLADERF_CHANNEL_RX(ch), &gain_actual) != 0)
            return -1;

        printf("Channel %d: Fs=%d, Freq=%ld, gain=%d\n", ch, samplerate_actual, frequency_actual, gain_actual);
    }

    // configure rx, this uses a "bladerf_channel_layout", BLADERF_RX_X2 configures for x2 RX
    if (bladerf_sync_config(dev, channel_layout, BLADERF_FORMAT_SC16_Q11_META, 32, 8192, 16, 3500) != 0)
        return -1;

    // enable, this uses a "bladerf_channel"
    for (int ch = 0; ch < n_channels; ch++)
    {
        if (bladerf_enable_module(dev, BLADERF_CHANNEL_RX(ch), true) != 0)
            return -1;
    }

    // do rx 5 times, check last sample
    printf("Starting rx, read_size = %d\n", read_size);

    for (int i = 0; i < 5; i++)
    {
        if (bladerf_sync_rx(dev, samples, block_size, &meta, 5000) != 0)
            return -1;

        if (meta.status & BLADERF_META_STATUS_OVERRUN)
            fprintf(stderr, "Overrun detected. %u valid samples were read.\n", meta.actual_count);

        printf("rx time %ld, last sample=%d\n", meta.timestamp, samples[block_size * 2 - 1]);
    }

    // clean up
    for (int ch = 0; ch < n_channels; ch++)
    {
        if (bladerf_enable_module(dev, BLADERF_CHANNEL_RX(ch), false) != 0)
            return -1;
    }

    free(samples);
    bladerf_close(dev);

    printf("Bye!\n");
    return 0;
}