ESP32 and Programming

To program the ESP32 is usually a bit of luck and sometimes pressing the reset button if you’re less lucky.

RTS and/or DTR should be able to reset the ESP32. Once it’s reliably reset, a download via netcat works. If I only had a program to reset RTS and/or DTR!

I found one here, changed it to toggle DTR instead of RTS as toggling RTS did not do anything. Now I can reset the ESP32 reliably. Full automation is achieved!

Here the DTR toggle program:

#include <stdio.h>
#include <stdlib.h>
#include <termios.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>


static struct termios oldterminfo;


void closeserial(int fd)
{
 tcsetattr(fd, TCSANOW, &oldterminfo);
 if (close(fd) < 0)
 perror("closeserial()");
}


int openserial(char *devicename)
{
 int fd;
 struct termios attr;

 if ((fd = open(devicename, O_RDWR)) == -1) {
 perror("openserial(): open()");
 return 0;
 }
 if (tcgetattr(fd, &oldterminfo) == -1) {
 perror("openserial(): tcgetattr()");
 return 0;
 }
 attr = oldterminfo;
 attr.c_cflag |= CRTSCTS | CLOCAL;
 attr.c_oflag = 0;
 if (tcflush(fd, TCIOFLUSH) == -1) {
 perror("openserial(): tcflush()");
 return 0;
 }
 if (tcsetattr(fd, TCSANOW, &attr) == -1) {
 perror("initserial(): tcsetattr()");
 return 0;
 }
 return fd;
}


int setSerial(int fd, int bitmask, int level)
{
 int status;

 if (ioctl(fd, TIOCMGET, &status) == -1) {
 perror("setSerial(): TIOCMGET");
 return 0;
 }
 if (level)
 status |= bitmask;
 else
 status &= ~bitmask;
 if (ioctl(fd, TIOCMSET, &status) == -1) {
 perror("setSerial(): TIOCMSET");
 return 0;
 }
 return 1;
}


int main(int argc, char *argv[])
{
 int fd;
 char *serialdev = "/dev/ttyUSB0";
 int bitmask;

 if (argc == 2) {
 serialdev = argv[1];
 }

 // printf("device: %s\n", serialdev);


 fd = openserial(serialdev);
 if (!fd) {
 fprintf(stderr, "Error while initializing %s.\n", serialdev);
 return 1;
 }

 bitmask = TIOCM_DTR; // alternatively TIOCM_RTS | TIOCM_DTR

 setSerial(fd, bitmask, 0);
 sleep(1); /* pause 1 second */
 setSerial(fd, bitmask, 1);

 closeserial(fd);
 return 0;
}

And the program to upload to the ESP (via netcat):

#!/bin/bash 
# 
# Upload JS file to ESP32 via wifi 
# 
# Usage: 
# uploadesp.sh JAVASCRIPTFILE IPADDRESS 
 
if [[ $# -ne 2 ]] ; then 
        echo "Usage: $0 JAVASCRIPTFILE IPADDRESS" 
        exit 20 
fi 
 
if [[ ! -f "$1" ]] ; then 
        echo "ERROR: Cannot read file \"$1\"" 
        exit 10 
fi 
 
dtr-toggle 
 
TMP="$(mktemp).js" 
espruino -n -o $TMP $1 
echo "Uploading to $2:23" 
nc $2 23 < $TMP >/dev/null 
 
# rm $TMP 
exit 0