Changing iq.frequency via Trigger

[broeckel]

I am trying to change the frequency in the iq module via a Trigger. Unfortunately doing so via the python API seems to be too slow. Hence, I need to change the FPGA code in order to achive a fast enough response.

I checked the verilog code of the different modules and I suspect that I simply need to add an additional input to the iq module which will change dynamically the value of the frequency. However, I was not able to find the frequency variable itself. My question is: What is the equivalent of the iq.frequency variable in the python API at the FPGA verilog level? I.e. what variable do I need to change in the verilog code in order to change iq.frequency?

[michaelcroquette]

The frequency register of the iq module has the adress 108:

frequency = FrequencyRegister(0x108, bits=_PHASEBITS,
                                  doc="frequency of iq demodulation [Hz]")

which correspond in the FPGA code to the variable shift_phase: if (addr==16'h108) shift_phase <= wdata[PHASEBITS-1:0];

Good luck !

[broeckel]

Hi @michaelcroquette Thanks a lot for the reply! I modified the FPGA code but now I am not quite sure how to upload the new code to the RedPitaya. Here is what I did:

1) I copied the pyrpl git to my local computer. 2) I installed Vivado 2015 (on Windows) 3) After modifying the Verilog code in the iq-module, I run "make" in the /pyrpl/fpga folder 4) I copied the resulting red_pitaya.bit file from the /out folder to the RedPitaya by following section 4.2.2.3.4.1 in https://redpitaya.readthedocs.io/en/latest/developerGuide/software/build/fpga/fpga.html (for OS version 1.04 or older)

Are these steps correct or do I need to do something else?

In the modified FPGA code I removed the line that you highlighted in the iq-block. I assume that due to this change I would not be able to set the iq.frequency in the Python code to particular value. However, I am still able to set the variable iq.frequency and printing it to the console gives me that value. Is my expectation correct that I would not be able to use iq.frequency in the python code when I remove that line from the iq-block in the FPGA code?

[broeckel]

I managed to load the new image on the RedPitaya. The steps that I described in my last comment work correctly, the issue was that if you load a custom image to the RedPitaya and start pyrpl with some existing comfiguration file, it will load a different red_pitaya.bin file and override your custom image. I had to set this functionality to false in the configuration file, then it works correctly.

I managed to test some modifications of the red_pitaya_iq_block.v code. For instance, setting iq.frequency to a fixed value works correctly. Now, I am trying to find a way to use one analog input of the RedPItaya to change the value of iq.frequency dynamically. Could you give me a hint what modules I would need to modify? I suspect I need to change red_pitaya_top.v, red_pitaya_dsp.v and red_pitaya_iq_block.v?