SDR (Software Defined Radio) » gr-osmosdr

The only difference I see when comparing the gr-osmosdr code to the gr-uhd code is this:

gr-osmosdr:

double uhd_source_c::set_center_freq( double freq, size_t chan ) {
#define APPLY_PPM_CORR(val, ppm) ((val) * (1.0 + (ppm) * 0.000001))

double corr_freq = APPLY_PPM_CORR( freq, _freq_corr );

// advanced tuning with tune_request_t
uhd::tune_request_t tune_req(corr_freq, _lo_offset);
_src->set_center_freq(tune_req, chan);

_center_freq = freq;

return get_center_freq(chan);
}

gr-uhd:

void usrp_block_impl::_cmd_handler_looffset(const pmt::pmt_t &lo_offset, int chan, const pmt::pmt_t &msg) {
if (pmt::dict_has_key(msg, CMD_FREQ_KEY)) {
// Then it's already taken care of
return;
}

double lo_offs = pmt::to_double(lo_offset);
::uhd::tune_request_t new_tune_request = _curr_tune_req[chan];
new_tune_request.rf_freq = new_tune_request.target_freq + lo_offs;
new_tune_request.rf_freq_policy = ::uhd::tune_request_t::POLICY_MANUAL;
new_tune_request.dsp_freq_policy = ::uhd::tune_request_t::POLICY_AUTO;

_update_curr_tune_req(new_tune_request, chan);
}

In gr-uhd they explicitly set the RF freq policy and DSP freq policy. I wonder if that is what's causing the difference.