Empyrean/Arduino Zero USB-UART Flow Control

ZeroUARTFlowControl.ino

uint8_t led = LED_BUILTIN;

void setup() {
  SerialUSB.begin(57600);
  pinMode(led, OUTPUT);
}

void loop() {
  if(SerialUSB.rts()) {
    digitalWrite(led, HIGH);
  }
  else {
    digitalWrite(led, LOW);
  }
}

#include <sys/ioctl.h>
#include <fcntl.h>
#include <sys/stat.h>

main()
{
    int fd;
    fd = open("/dev/ttyACM0",O_RDWR | O_NOCTTY );

    int RTS_flag;
    RTS_flag = TIOCM_RTS;
    getchar();
    ioctl(fd,TIOCMBIS,&RTS_flag);//Set RTS pin
    getchar();
    ioctl(fd,TIOCMBIC,&RTS_flag);//Clear RTS pin
    close(fd);
}