Change Pi Pico Serial Pins

OK, I have it working now! :partying_face:

I changed my platfomio.ini to this:

[env:pico]
;platform = raspberrypi
platform = https://github.com/maxgerhardt/platform-raspberrypi.git
board = pico
framework = arduino
board_build.core = earlephilhower
board_build.filesystem_size = 0.5m

platform_packages =
    maxgerhardt/framework-arduinopico@https://github.com/earlephilhower/arduino-pico.git#master

And the demo code in main.cpp looks like this:

#include <Arduino.h>

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);

  Serial1.setRX(17u);
  Serial1.setTX(16u);
  Serial1.begin(19200);
}

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);  // turn the LED on (HIGH is the voltage level)
  delay(1000);                            // wait for a second
  digitalWrite(LED_BUILTIN, LOW);   // turn the LED off by making the voltage LOW
  delay(1000);                            // wait for a second
  Serial1.println("Hello World!");
}