lower voltage at rf output than expected

[nyagaka]

Hi,

So I was trying to familiarize myself with the board and how to stream data from the inputs directly to the output. So, what I did was setup the ADC, DAC, Clock wizard and The ZYNQ-7 block to have a setup where I could stream in data through the RF input into the ADC and stream out the same exact data to the DAC outputs and subsequently to the RF output. The only issue was that I wasn't getting an exact replica of my input at the output. I was instead getting around a tenth of my input at the output so for an input of 250mVpp I would get 35mVpp or something of that sort.I almost feel like I may not fully appreciate the workings of the device (in particular the DAC perhaps) and it's similalrly unclear from the documentation.

Any help on this and some further reference for me to read would be much appreciated.

[nyagaka]

I'll probably try this tomorrow but I think this is because of the HV setting on the jumpers when I set up the board. Likely, I need the LV configuration to increase the gain and get a 1:1. Not sure if it'll work but seems the most logical thus far.

[redpitaya]

Hello nyagaka,

Moving this topic to FPGA-related topics.

We apologize for not having clear instructions on how to program Red Pitaya using the Vivado Logic Blocks.

Please check whether the jumpers are set correctly.

The projects here might be useful for you (they use verilog and VHDL code instead of the blocks):
https://lniv.fe.uni-lj.si/redpitaya/
https://redpitaya-knowledge-base.readth ... red-pitaya

[sslerose]

I'll probably try this tomorrow but I think this is because of the HV setting on the jumpers when I set up the board. Likely, I need the LV configuration to increase the gain and get a 1:1. Not sure if it'll work but seems the most logical thus far.

I have my board set to LV on the jumpers and a function generator set to 1V peak-to-peak sine waves (so +- 0.5V). My external oscilloscope seems to amplifies them to +- 1V sine waves, as does my Red Pitaya's oscilloscope.

However, I have the same problem where the data stream through the ADC/DAC drops the amplitude by a factor of 10. Interestingly, the waves are +- 50mV, which is consistent with a drop of the function generators intended 1V peak-to-peak rather than the seemingly amplified voltage I get from either oscilloscope.

[nyagaka]

The first issue you posted about is with regards to the impedance matching between the signal generator and the board. That can be fixed by setting the generator to high Z impedance.

The second issue which sounds like what I faxed directly related to the jumper cables. I tried again earlier today and the issue was sorted with the jumpers on the LV thankfully. Hopefully you can figure out why your output is sniffed by a tenth.