USART RXRDY interrupt with Arduino Due

Using Arduino Programming Questions
#1

Hello,

I want to use the USART RXRDY interrupt to receive data on Serial2 (Pin17) with an arduino due.
I tried this simple program that just toggle a LED when a byte is received on Serial2 = USART1-RX = Arduino Due Pin 17 (RX2).
Does someone can explain me why this simple program doesn't work ?

// Toggle Built-in LED when a byte is received on Serial2 = USART1-RX = Arduino Due Pin 17 (RX2)

volatile char data ;
volatile char led_state = 0 ;

void USART1_Handler (void) __attribute__ ((weak));
void USART1_Handler(void)
{
  data = USART1->US_RHR;
  digitalWrite(LED_BUILTIN, (led_state++)%2);
}

void setup() 
{  
  pinMode(LED_BUILTIN, OUTPUT);
  Serial2.begin(115200);
  
  // Enable interrupts on end of receive
  USART1->US_IER = US_IER_RXRDY;
  NVIC_EnableIRQ(USART1_IRQn);  
}

void loop() 
{
}

Thanks,
Stephane

#2

Both Serial1, Serial2, Serial3 are using interrupts. Therefore you can't write your own USART1_Handler() code as you did. Before writing your own USART1_Handler(), you would have to alter variant.h.

See this thread, reply #4:

Anyway, you don't have to alter anything to read something from USART1 (Serial2). See this example sketch to read bytes from Serial1:

/*********************************************************************/
/* Jumper between RX1 and TX2, and another one between TX1 and RX2   */
/*********************************************************************/

char c = 0;
void setup() {
 
  Serial.begin(250000);
  Serial1.begin(5000000);
  Serial2.begin(5000000); 
  Serial2.print("Hello");
}


void loop() {
  String s;
  s.reserve(10);
  s = "";

  while (Serial1.available() > 0) {
    c = Serial1.read();
    s += c;

  }
  if (s.length() > 0) {
    Serial.println(s);
    Serial2.print(s);
  }
  delay(1000);
}
#3

Thanks for your answer.
I understand my mistake.
Considering the topic you told me about DMA and USART, I think I will use the DMA controller to read USART1 instead of interrupts.

#4