7 Jun
2017
7 Jun
'17
7:51 p.m.
Hi Harald,
On Fri, May 26, 2017 at 1:59 PM, Harald Welte <laforge(a)gnumonks.org> wrote:
I was wondering if it is possible to generate a TDMA
frame sync output
on a GPIO line of a USRP device (and/or any other SDR supported by
osmo-trx). This way it would be much easier to do e.g. BER testing
by using a pure waveform/pattern generator for the "MS side".
I recently tested GSM frame triggering with a B210. The UHD code
itself for GPIO triggering is fairly straightforward.
/* Configure GPIO-0 pin*/
usrp->set_gpio_attr("FP0", "CTRL", 0x00);
usrp->set_gpio_attr("FP0", "DDR", 0x01);
/* Set rise and fall times */
usrp->set_command_time(TIME_A);
usrp->set_gpio_attr("FP0", "OUT", 0x01);
usrp->set_command_time(TIME_B);
usrp->set_gpio_attr("FP0", "OUT", 0x00);
I tested the frame trigger using the B210 with osmo-trx in a new
signal generator application (to be announced shortly), which works
fine.
But, when I attempt to trigger with full-duplex osmo-trx, the trigger
becomes unstable for reasons that I do not fully understand. I'm still
looking into the cause.
So right now we can generate a frame trigger for the BTS downlink,
but, unfortunately, not while the uplink receiver is enabled.
-TT