You should be able to use the standard esp32 dev module board settings for a pico-v3.
Do you get the download message on uart if you hold down gpio0 and reset the board?

Enabling system trace requires a significant amount of memory, so it is disabled in arduino-esp32

Please make sure you are using 2.0.15. There was a fix specifically for Serial blocking on HWCDC. In fact, remove the "Arduino ESP32 Boards" from board manager completely unless you are using the Arduino branded esp32. Make sure you have "USB CDC On Boot" set to enabled and the "JTAG adapter" set to...

Add `log_v("Send Header: '%s'", header.c_str());` to sendHeader

Any reason you can't just use Serial1? Example code
Note that the RX on the esp needs to connect to the TX on the serial device.

There is also a pre-built called 'Minimal SPIFFS (1.9MB APP with OTA/190KB SPIFFS)'
https://github.com/espressif/arduino-es ... spiffs.csv

That link also shows the define macros you should set before you call initArduino that match the settings from the tools menu.

The default on esp32-s3 is 8 & 9, but you can assign them to whatever you want with Wire.begin(sda, scl);

Take out all the softwareSerial stuff. You are starting up Serial2 correctly. Take out the stuff where you are reading Serial2 at the beginning of loop(). Change the while to look something like this: while (Serial2.available() > 0) { char nextbyte = Serial2.read(); Serial.print(nextbyte); if (gps.e...