Hi Harald,
On Fri, May 26, 2017 at 1:59 PM, Harald Welte laforge@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