Thanks for your suggestions.
What puzzled me was that with the same connection untouched, both blink and serial worked if I chose the board as Adafruit Feather F405 or Generic F407VE. It just would not work if I chose it as Generic F405RG.
Code: Select all
#define LED PC1
HardwareSerial Serial6(PC7, PC6);
void setup()
{
Serial6.begin(9600); // set to 14400 if choosing Feather F405 which assumes 12MHz clock
pinMode(LED, OUTPUT);
}
void loop()
{
Serial6.print("loop test");
digitalWrite(LED, HIGH);
delay(250); // actual blink period is 0.375s if choosing Feather F405 since my board has 8MHz clock
digitalWrite(LED, LOW);
delay(250);
}