Sorry for the delay... my STAMP_PICO project was momentarily shelved but I just resurrected it and found your response.
I will definitely try your suggestion since I would like to keep the native port to flash but I need another UART.
General tinkerer, hardware guy with lots of C background on 8051 and ARM and a bit of Arduino.
Posts made by didier9
RE: Accessing second UART on M5Stamp-PICO
RE: new m5stack: Failed to write to target RAM (result was 01070000)
I had weird problems like this with an M5Stamp-PICO until I put more capacitance across the bus (5V and 3.3V). I used a couple of tantalum capacitors I had on hand, not sure the value, probably 33uF. I was powering the device through the USB serial adapter and apparently it was power limited.
I have had no problem whatsoever since then.