[Discuss-gnuradio] Firmware issue: Send a constant signal with the xcvr2450 dboard

[Matthias Schäfer]

 Hi List,
I'm currently working on a standalone firmware app for USRP2. My goal is 
to send a constant signal with the xcvr2450 dboard. I skipped the tuning 
via firmware by doing this prior from a host using the simple_usrp c++ 
interface:

uhd::usrp::simple_usrp::sptr sdev = uhd::usrp::simple_usrp::make(args);
uhd::device::sptr dev = sdev->get_device();
sdev->set_tx_rate(rate);
sdev->set_tx_freq(freq);
sdev->set_tx_gain(gain);

===============
So back to the firmware. Assuming the tuning of the dboard is properly 
done from host, I basically understood the way sending is done as follows:

1. Wait for the buffer pool to become idle:

while((buffer_pool_status->status & BPS_IDLE(DSP_TX_BUF_0)) == 0)
    ;

2. Copy the data which should be send to the DSP into the DSP tx-buffer:

uint32_t *p = buffer_ram(DSP_TX_BUF_0);
uint32_t sample = (32000 << 16) | 0; // for example
for (i = 0; i < BP_NLINE; i++) {
    p[i] = sample;
}

3. Send the data to the DSP:

bp_send_from_buf(DSP_TX_BUF_0, PORT_DSP, 1, 0, BP_LAST_LINE);

4. Wait until transaction is done or an error occured

while((buffer_pool_status->status & (BPS_DONE(DSP_TX_BUF_0) | 
BPS_ERROR(DSP_TX_BUF_0))) == 0)
        ;

5. Clear the status flags and redo the whole procedure

bp_clear_buf(DSP_TX_BUF_0);
// goto 1.

===============

Unfortunately this doesn't work for me like expected. I tried it in 
several variations and listened with another usrp2 for a signal but 
nothing happens. I think I understood something wrong and forgot 
something but it's hard for me to see the problem.

So maybe you guys can help me out with that.

Thanks in advance!

Cheers,
Matthias