Thank you Jeff and Sam, I found now also the gpio.cpp example. Really helpful to get familiar with GPIO.
>> To accomplish what you're talking about, I think you'd just need to use >> timed commands >>on both set_tx_rate() and set_gpio_attr(). If these are set >> to execute simultaneously, the >>GPIO line you set will go high on the same >> clock cycle as the LO retune. In fact in my code which is based on the “tx_samples_from_file” example I start transmitting my data in the file in the future with tx_metadata_t time specification and with timed commands I set set_gpio_attr() to the same point in future. But this gives me just 1 output pulse in GPIO what is not sufficient for my application. I am transmitting in continuous mode (a fixed modulation in a while loop) and my center frequency stays fix during the whole transmission whereas with my data in the file I am modulating the center frequency to discrete frequencies in the whole bandwidth of 160MHz. I measured a transition time of the usrp of around 20ns between different frequencies in my modulation. To be able to postprocess my RF signal I would like to have a pulse each time the tx-frequency is changing. As the ATR is just showing if the usrp is transmitting, receiving or idle it is not really helpful And putting set_gpio_attr() in the while loop for my continuous transmission is slowing down the streaming and causes underruns. Do you think of any other solution to get a pulse each time the transmission frequency of the USRP is changing? Thomas From: Sam Reiter Sent: Tuesday, January 14, 2020 6:44 PM To: Jeff S Cc: usrp-users@lists.ettus.com; Thomas Harder Subject: Re: [USRP-users] using GPIO output to trigger external RF switches Thomas, To accomplish what you're talking about, I think you'd just need to use timed commands on both set_tx_rate() and set_gpio_attr(). If these are set to execute simultaneously, the GPIO line you set will go high on the same clock cycle as the LO retune. Sam On Tue, Jan 14, 2020 at 5:59 AM Jeff S via USRP-users <usrp-users@lists.ettus.com> wrote: Thomas, I am looking at GPIO right now as well. As to your question #2 on examples, I compiled and am able to run the example I found in the UHD software: uhd/host/examples/gpio.cpp I am able to set individual data lines to experiment with (and eventually use as a roadmap for my development) using commands like: ./gpio --dwell 0 --bitbang --ddr 0x00ff --out 0x0055 which I verified works using a logic analyzer. I eventually want to try to create a keying loop, but that may take some FPGA control (?). Jeff From: USRP-users <usrp-users-boun...@lists.ettus.com> on behalf of Thomas Harder via USRP-users <usrp-users@lists.ettus.com> Sent: Tuesday, January 14, 2020 5:07 AM To: usrp-users@lists.ettus.com <usrp-users@lists.ettus.com> Subject: [USRP-users] using GPIO output to trigger external RF switches Hi, I am continuously transmitting a waveform with several RF with 200MSPS with my USRP X310 (modified code on the basis of “tx_samples_from_file.cpp” with a waveform in a .dat file). I would like to get a trigger signal from the USRP when it is changing the tx- frequency which I set in my .dat file. Could the GPIO deliver this trigger without changing the image? I am using the SRAM image with UHD 3.14.1 A second question is concerning the GPIO example on https://files.ettus.com/manual/page_gpio_api.html. I copied and paced it in the “tx_waveforms” example just changing the usrp device handle to “usrp” but when I compiled it and started tx, I couldn’t measure any tension on PIN 4 and 6 as defined in the example. Are there more examples how to program the GPIO? Thank you, Thomas _______________________________________________ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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