Strange TX calibration behavior

Projects LimeSDR
1

I’m seeing something odd when setting the transmit gain via Soapy. When I initialize in the following order:
//TX settings
if (SoapySDRDevice_setSampleRate(state->sdr, SOAPY_SDR_TX, 0, state->sample_rate) != 0)
{
printf(“TX setSampleRate 0 fail: %s\n”, SoapySDRDevice_lastError());
return EXIT_FAILURE;
}
if (SoapySDRDevice_setFrequency(state->sdr, SOAPY_SDR_TX, 0, state->tx_frequency, NULL) != 0)
{
printf(“setFrequency fail: %s\n”, SoapySDRDevice_lastError());
return EXIT_FAILURE;
}
if (SoapySDRDevice_setAntenna(state->sdr, SOAPY_SDR_TX, 0, state->tx_port) != 0)
{
printf(“setAntenna fail: %s\n”, SoapySDRDevice_lastError());
return EXIT_FAILURE;
}
if (SoapySDRDevice_setBandwidth(state->sdr, SOAPY_SDR_TX, 0, state->tx_bandwidth) != 0)
{
printf(“setBandwidth fail: %s\n”, SoapySDRDevice_lastError());
return EXIT_FAILURE;
}
if (SoapySDRDevice_setGain(state->sdr, SOAPY_SDR_TX, 0, state->tx_gain) != 0)
{
printf(“setGain fail: %s\n”, SoapySDRDevice_lastError());
return EXIT_FAILURE;
}

I get the following message:
[ERROR] Tx Calibration: MCU error 5 (Loopback signal weak: not connected/insufficient gain?)

If I move the setGain call to the beginning of this block of code the TX cal works just fine. Is there some order dependency on TX (and/or RX) setup?

2

It appears that SoapySDRDevice_setBandwidth automatically calls filter calibration procedure. So you have to set your gain before it, or just manually call calibration after you set the gain.

3

Thanks for the heads up. Are you aware of any other order dependencies I might need to be aware of?