I am testing this again in my electronics lab. Here are today’s findings:
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I was mistaken when I wondered (in my earlier post today) if the power rail and ground pins changed in position. I see now from the diagram I was using yesterday, that they were where @ansonhe97 has listed them in the new diagram. I was upstairs when I wrote my first post this morning, so I didn’t remember correctly. But I was in fact using the power pins where they were indicated in both the original and the new diagrams. Checking the voltage on both pins now just to be sure, I do read about 3v3 on pin 24, and around 5v on pin 26.
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There doesn’t seem to be a Serial2 object recognized by the Arduino IDE for the SAMD21 library. I grepped for it under the /home/user/snap directory where the Seeed stuff gets installed by default–but it’s not any source or header file. See the output of grep, here: https://pastebin.com/mQ3N6j3q
That said, it IS in the Arduino core code, in /snap/arduino/. I didn’t post a grep output file as it’s in LOT of places in that directory tree–but the SAMD compiler is apparently not looking there. This brings up a question:
Should we be installing the Arduino SAMD Boards library as well, in the Boards Managers utility in the IDE? I don’t know if the arm-none-eabi-g++ compiler that Seeed Studios has configured for this board is actually looking there…so I thought I should at least ask.
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SerialUSB IS the serial object we need to be using in order to get output from the Arduino serial monitor. I am positive of that. I’ve tried using the “Serial” object in code many times (including again just now), and there IS NO OUTPUT on the serial monitor. Change all the “Serial” calls to “SerialUSB” and you get output immediately.
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I strongly suspect that here is still a major issue with the serial functionality of this Odyssey board, in general. Although I no longer seem to lock up the serial monitor after trying to send characters to the board three or four times, I still must force-kill it in Ubuntu. It seems that I can now send characters as many times as I’d like, and the serial monitor (and IDE) continues to function. However when I then try to close the serial monitor using the little ‘X’ button in its upper right corner, the entire IDE locks up. Neither the IDE nor the serial monitor responds after that–and I must force-kill them and start over. I didn’t try this on Windows yet–only Ubuntu. Maybe @wx4cb or someone else can confirm this behavior.
So although I appreciate it that you looked into this issue @ansonhe97, it’s far from being correct. The only thing that I can really see that’s changed is your diagram of the pins on the 4-pin header (swapped Rx/Tx positions), but I cannot test this because the Serial2 object IS NOT recognized by the SAMD21 compiler (arm-none-eabi-g++). Therefore I cannot test and farther.
I am happy to report that placing the logic analyzer on the Rx/Tx pins on the 4-pin header no long causes the board to reset (YAY!!!), and I do NOT see that semi-symmetric square wave signal. I suspect that is because I was actually reading the RST pin signal (LOL!!!), which likely explains the weird waveform I was seeing previously.
TB