On the Hunt for a Serial Problem

PicoCalc
21

Try flashing Picoware and using the Serial Terminal app. It uses GP4 and GP5, and I did my testing with the PicoCalc (using the Serial Terminal app) and Flipper Zero (using the UART Terminal app)

22

I use GP4 and GP5 for COM2: since they are brought out to the external connectors. There’s no problem at all. No hardware mod needed. Instead of relying on schematics, try these things yourself.
OPTION SERIAL CONSOLE COM2,GP4,GP5,BOTH

23

You are correct that GP2-GP5, GP21, GP28 are connected to J703, but these lines are also connected to U301 (ESP-PSRAM64H). GP8/GP9 are listed in the diagram with UART1, meaning no other function. I don’t know whether U301 survives the voltage levels produced by an RS232 adapter, with GP8/GP9 the only damage would be a Pico board that can be replaced in a short time at low cost, replacing the PicoCalc (if damaged) would be more problematic.

I am normally very careful giving advice, I do not want to be responsible for possible damage.

24

Thanks @Toml_12953 @ernst @jblanked for the input and advice, it seems that serial comms is a bit of a minefield currently with Picocalc and Picomite, I saw a video where it was said that the two dip switches configure some routings of the UART pins to either the STM32 or the Pico, but that doesn’t seem correct?

25

My experience with the UART on the Picocalc has been nerve racking but eventually settled on using UART1 on GP8/GP9. Here is what I found during a week of digging. I have a Pico W in the Picocalc, everything done under Micrpython:

  • Tried using UART1 on GP4/GP5 to no luck at all
  • UART0 on GP0/GP1 is super weird, I tried reading the UART of a Heltec 32 V3 but could not get any data. I matched the baud rate and had a ground shared between the devices. I even measured with a scope that the levels were at 3.3v because I thought it was an electrical problem. To make things even more weird I hooked up another Pico sending data to the PIcocalc on UART0 and everything went fine. All 3 devices in this trio, both Picos and Heltec had the same UART port parameters. I gave up.
  • I ended up lifting GP8/GP9 which work with no issue and I can read fine any device through UART.
26

UART0 tied to GPIO0 and GPIO1 is fed into the USB-C port of the PicoCalc as a USB-serial device, which is probably why trying to use it as you were was not doing what you intended.

27

Agreed but what baffles me is that reading another pico was successful, I set up a pico to just write a string, of various lengths, every 1/10the second and the picocalc read it successfully with the same piece of code that it could not read the Heltec board.

Whe I connected the Heltec it didn’t even want to go beyond the any() check so literally ot was like zero data.

28

Are you using an H-variant? If not, have you checked your solder joints?

29

The fact that it works when I connect another pico is testimony to the solder joints. Yes it is a Header version.