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

[Matthias Schäfer]

 Am 16.09.2010 07:49, schrieb Eric Blossom:
> On Wed, Sep 15, 2010 at 05:55:12PM +0200, Matthias Schäfer wrote:
>>  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
> A couple of things.  32000 is likely to be too big and will probably
> result in clipping.  Try 3200 to start with.
>
> It's unlikely that f/w can write samples to the buffer fast enough to
> keep the data streaming. However in your case, you only need to
> initialize the samples in the buffer once, then you can just keep
> sending it over and over.  
>
> Do (2) once.
>
> // Start in known good state (IDLE)
> bp_clear_buf(DSP_TX_BUF_0);
>
> // start first buffer xfer
> bp_send_from_buf(DSP_TX_BUF_0, PORT_DSP, 1, 0, BP_LAST_LINE);
>
> while (1){
>
>   // wait for xfer to complete
>   while ((buffer_pool_status->status &
>           (BPS_DONE(DSP_TX_BUF_0) | BPS_ERROR(DSP_TX_BUF_0))) == 0)
>     ;
>
>   // Reset flags
>   bp_clear_buf(DSP_TX_BUF_0);
>
>   // start next xfer
>   bp_send_from_buf(DSP_TX_BUF_0, PORT_DSP, 1, 0, BP_LAST_LINE);
> }
>
>
> Eric
Hi Eric,
thank for your fast reply. I tried the things you told me but it doesn't
work nevertheless. I'm using the txrx_uhd f/w with the additional void
SEND_DATA() (see below). After tuning the USRP2 with the mentioned
host-app (see above), I'm sending a UDP packet to the USRP2 with a
special port which becomes filtered by the eth_pkt_inspector which then
invokes SEND_DATA(). The serial port then tells me the following:

Waiting for the buffer pool.
Buffer pool idles. Filling buffer.
Filled buffer. Start sending.
Done.
Done.

and than the USRP2 stucks in the inner waiting-loop until I restart it.
If the debug-symbols (putstr) make any problems here, I tried it several
times without serial port but it didn't have any effect. The H/W seems
to be okay, because sending and receiving with grc works fine.

Do I maybe have to set some dboard/buffer pool flags before sending?
Does my tuning procedure maybe leave the dboard in a "no-sending"-state?

static void SEND_DATA () {
    putstr("Waiting for the buffer pool.\n");

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

    putstr("Buffer pool idles. Filling buffer.\n");

    // fill buffer
    uint32_t *p = buffer_ram(DSP_TX_BUF_0);
    uint32_t i;
    uint32_t sample = (3200 << 16) | 0;

    for (i = 0; i < BP_NLINES; i++) {
        p[i] = sample;
    }

    putstr("Filled buffer. Start sending\n");

    bp_clear_buf(DSP_TX_BUF_0);

    // first xfer
    bp_send_from_buf(DSP_TX_BUF_0, PORT_DSP, 1, 0, BP_LAST_LINE);

    while (1) {

        // wait for xfer to complete
        while ((buffer_pool_status->status &
              (BPS_DONE(DSP_TX_BUF_0) | BPS_ERROR(DSP_TX_BUF_0))) == 0)
            ;

        putstr("Done.\n");

        bp_clear_buf(DSP_TX_BUF_0);

        // fire it off
        bp_send_from_buf(DSP_TX_BUF_0, PORT_DSP, 1, 0, BP_LAST_LINE);
    }
}


Cheers,
Matthias