#RFM9x RP2040 USB interference at high power

1 messages · Page 1 of 1 (latest)

timber dew
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setting the transmit power to 23 on the feather RP2040 RFM9x board causes issues with USB connections. On my M1 Mac, it either causes the serial port to freeze until the USB is disconnected or sometimes it disconnects the CIRCUITPY drive on every transmission and the board resets. On a Rasberry Pi 400, the USB connection (monitored via tio) disconnects with every transmission. TH board appear to keep running most of the time . It occasionally resets to Safe Mode. Running the board from a wall supply, it transmits normally. Also running the same code on a feather M0 RFM9x, works normally -- no issues. Of course, the issue can be intermittent - it does not always occur 😦

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@pliant rover I started this thread to track this issue -- please add to it.

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I hooked up a PPK2 power profiler to the rp2040 RFM9x board. at tx_power=23 it draws an additional 50 mA (~150 vs typical ~100 for tx_power = 13 - the default)

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I have not seen any issues on the RP2040 RFM9x when running with tx_power = 13 (default)

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So far -- all of my testing has been with CircuitPython. I'll try it with Arduino soon.

timber dew
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The issue also appears to be present with Arduino (RadioHead) -- at least it causes the USB port on the Mac to hang -- not quite as much visblility into the behavior as with CP 😉 but it does seem to be an issue with the HW in general, not just CP.

pliant rover
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I was seeing the same issue above on my M2 Mac. I also tried stepping down the transmit power and around 18 or 19 is when it started to disconnect too often to use. The other issue I was seeing that may or may not be related is that when running off a 350mAh adafruit LiPo plugged into the battery port, I occasionally see the same symptoms of the board rebooting and occasionally swapping into safe mode. So far in my minimal testing, these issues have gone away (at tx_power=23) when running off a USB cell phone chargers and not using the LiPo or a computer as a power source

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I also changed the bandwidth and spread factor on my devices as part of my testing because I was trying to increase range, but don't know if that had any effect on the resetting issues.

timber dew
timber dew
pliant rover
# timber dew <@340702106702839809> What are you using for an antenna? Switching to a uFL ante...

Spring antenna. I asked above, but it doesn't look like the 1/2 wave whip antenna that you are using is sold by adafruit anymore, I was trying to figure out why. I don't have a uFL or SMA antenna around to test with, will need to buy something. But I also won't be able to put the antenna too far from the board in the project box that I need, so I think I still have to switch boards if antenna distance is the answer.