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RXD is defined as IO20 (pin 30), but gets labeled as IO21/RXI
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TXD is defined as IO21 (pin 31), but gets labeled as IO20/TXO
Easiest way to fix this appears to be updating/correcting the labels to IO20/RXI and IO21/TXO.
Example needs added to the getting started guide on using these two UART pins:
void setup()
{
Serial.begin(115200); // USB CDC Serial-overUSB
Serial.println(“Serial: Begin”);
Serial1.begin(115200, SERIAL_8N1, 20, 21); // rxPin=20, txPin=21
Serial1.println(“Serial1: Begin”);
}
void loop() {
Serial.println(“Serial”);
Serial1.println(“Serial1”);
delay(3000);
}