Macchina M2-B Hacking Notes

history.md

cli history

miniterm.py `udevserial -v ID_MODEL=Arduino_Due -v SUBSYSTEM=tty` 115200 --raw
esptool32 --port `udevserial -v ID_MODEL=Arduino_Due -v SUBSYSTEM=tty` --before no_reset --after no_reset --baud 115200 write_flash 0x10000 ./build/gatt_server_demos.bin

mac32.ino

#include <OBD2.h>
#include <DueTimer.h>
#include "SamNonDuePin.h"

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

const int XB_nRST = X4;
const int XB_GPIO0 = 56;
const int LED_YELLOW = X0;

int doDelay = 0;

void setup()
{
  SerialUSB.begin(234000);
	Serial.begin(115200);

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

  pinModeNonDue(XB_nRST, OUTPUT);
  pinModeNonDue(XB_GPIO0, OUTPUT);

  digitalWriteNonDue(XB_nRST, HIGH);
  digitalWriteNonDue(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;
  }
}

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());
  }
}

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

  while(SerialUSB.available()) {
    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);

      return;
    }

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

    // 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(234000);

      digitalWriteNonDue(XB_GPIO0, LOW);

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

notes.md

ESP32

Flashing the ESP32 was the first thing needing attention. I wanted to be able to flash the device without removing it from the socket.

Pass-through flashing

The plan. Put the ESP32 into flashmode via nRST GPIO0 toggling. Bring both LOW then bring nRST back up. Then esptool32 can be coerced into flashing the chip. There is still a bit of manual intervention but I got it working.

Steps

Using mac32.ino send b over the USB serial port to enter bootmode.

> b

Reseting ESP32
Delay: 500.
> ets Jun  8 2016 00:22:57

rst:0x1 (POWERON_RESET),boot:0x3 (DOWNLOAD_BOOT(UART0/UART1/SDIO_REI_REO_V2))
waiting for download

If using a serial terminal disconnect, there is nothing else to be done without resetting the M2.

Now you can start flashing the ESP32 with esptool32. The differences from normal use are the inclusion of --before no_reset and --after no_reset. You have to reset and re-enter bootmode for each file being flashed, this is a shortcoming in the code at the moment.