When I originally bought this device, the default firmware supported TFTP, so I installed the initramfs version that when and then upgraded. (I think. It's been about a year. But I don't remember having to open it up.) However it looks like due to changes from 23.05, this device needs a fresh install, and the only way to do that is serial access. I'm having a heck of a time getting it. I THINK the problem is the pinout, but at this point I'm not really sure.
This is the closest I've found to the information I'm looking for, but it's slightly different.
This is the cable I'm using. It's a 3.3V, which matches what I've heard is most common, as well as multimeter readings.
I found a 4 pin header on the board labelled "console", with side access. Sounds right. However the individual pins are not labelled and it doesn't seem to match the topic above. The orientation is horizontal. I tried "rotating" in both directions, but nothing.
Minicom is set up for 115200 8N1 | NOR, with /dev/ttyUSB0 as the device. But after many, many different combinations of plugging things in, nothing has ever showed up in minicom.
I haven't plugged in the red wire because I guess that's extra power and you can fry the board, but I tried a bunch of other combinations. I tried to figure out the pins myself based on this article. Results were... inconsclusive. I have very little experience with a multimeter and probably have no idea what I'm doing.
Power ground: I put the multimeter on the lowest resistance setting, put one probe on the ground of the power plug, then tried each of the 4 serial pins. None of them reacted. I have no idea what the means. I wasn't able to identify the ground pin with this method.
Pin 1 - Didn't react with anything.
Pins 2-3 - Wildly fluctacting, so based on the above guide I think one is VCC and one is data.
Pins 2-4 - Looks like 1.7V.
Pins 3-4 - Looks like 3.3V.
So, from front to back, this is what I THINK the pins should be based on testing.
Pin 1 - RX - Never reacted, presumably because no incoming data.
Pin 2 - TX - Would make sense being next to RX, and read large fluctuations with pin 3.
Pin 3 - Ground - Based on the above guide, should react with TX.
Pin 4 - VCC - Shows 3.3V with 3, but no fluctuations with 2.
So I plugged it in accordingly (again, except VCC) and booted. Nothing in minicom. I tried switching RX and TX just in case. Still nothing.
The unit itself continues to work fine if I let it fully boot. I just can't get serial on it. What am I missing?