ESP32_flasher.INO

#include "SamNonDuePin.h"

bool led = 0;
bool toggleBootMode = false;
bool passThrough = false;
bool pipe = false;

const int XB_nRST = X4;
const int XB_GPIO0 = 29;
const int LED_YELLOW = X0;

int doDelay = 0;

void setup()
{

  while (!Serial) ;
  SerialUSB.begin(115200);
  Serial.begin(115200);

  SerialUSB.println(printf("System Reset"));
  SerialUSB.println("> ");

  pinModeNonDue(XB_nRST, OUTPUT);
  digitalWriteNonDue(XB_nRST, HIGH);
  
  pinMode(XB_GPIO0, OUTPUT);
  digitalWrite(XB_GPIO0, HIGH);

  pinModeNonDue(LED_YELLOW, OUTPUT);
  digitalWriteNonDue(LED_YELLOW, LOW);

  // reboot ESP32 on startup
  digitalWriteNonDue(XB_nRST, LOW);

  toggleBootMode = true;
  doDelay = 500;
}

void loop()
{
  if(doDelay > 0) {
    SerialUSB.print("Delay: ");
    SerialUSB.print(doDelay);

    delay(doDelay);

    SerialUSB.print(".\n> ");

    doDelay = 0;
  }

  if(toggleBootMode) {
    digitalWriteNonDue(XB_nRST, HIGH);
    toggleBootMode = false;
  }

  while(SerialUSB.available()) {

serialEventUSB();

  }
}

void serialEvent() {
  // 'activity' light
  digitalWriteNonDue(LED_YELLOW, led ? HIGH : LOW);
  led = led ? 0 : 1;

  // Serial data from XB_ can just be passed straight through
  while(Serial.available()) {
    SerialUSB.write((uint8_t)Serial.read());
    SerialUSB.flush();
  }
}

void serialEventUSB() {
  // 'activity' light
  digitalWriteNonDue(LED_YELLOW, led ? HIGH : LOW);
  led = led ? 0 : 1;
    uint8_t c = SerialUSB.read();

    if(pipe && c == 0x03) {
      pipe = false;
      SerialUSB.println("Ending pipe");

      return;
    }

    // if already in flash mode just write and stop
    if(pipe || passThrough) {
      Serial.write(c);
      Serial.flush();
      return;
    }

    // proper data coming back from ESP32 can be passed back
    SerialUSB.write(c);
    SerialUSB.flush();

    // simple command set
    // b: enter boot mode
    // r: reset

    // both b and r lower nRST
    // and toggle bootmode (back up in 500ms)
    if(c == 'b' || c == 'r') {
      SerialUSB.println("\n\nReseting ESP32");

      digitalWriteNonDue(XB_nRST, LOW);

      toggleBootMode = true;
      doDelay = 500;
    }

    // b also lowers GPIO0 and enables pass-through
    if(c == 'b') {
      Serial.begin(115200);

      digitalWrite(XB_GPIO0, LOW);

      passThrough = true;
    } else if(c == 'p') {
      SerialUSB.println("\nPiping data to ESP32");
      pipe = true;
    } else if(c == '\n') {
      SerialUSB.print("> ");
    }
}