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etherkit / Si5351Arduino

Library for the Si5351 clock generator IC in the Arduino environment
GNU General Public License v3.0
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Jittering output frequency #83

Open jj01101010 opened 2 years ago

jj01101010 commented 2 years ago

Hi. I bought a SI5351 dev board from amazon loaded in this libary and started running the example script. The serial output clearly sais to me that the PLLs are locked and the chip is ready to go, but when I connect my oscilloscope to one of the outputs (so far I tested CLK0 and CLK1), I only see a jittery frequency (about +- 1MHz). So far I managed to get a fixed frequency by accident, but as soon as I restarted the arduino the frequency was jittery again. I already measured the Input Clock, which is perfectly stable. I also tried to change the input capacitences in the init function. Nothing seems to fix the error. I hope someone with a little more understanding about this chip can help me :)

ka7u commented 1 year ago

I found by trial and error that if I set CLK1 to 10KHz, then I have minimal jitter from 8KHz to 170MHz on CLK0. I need to figure out what the relationship is between CLK1 and CLK0. It is necessary to terminate the clock outputs into a 50 ohm load as well.