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This comm sketch simply read incoming bytes from the UART 1 where a device is attached. It works normally on a real Arduino device. But on ESP32, it makes it continuously reboot with the following messages:

([UPDATE] Note that there is no reboot on ESP32 is I use Serial2 instead of Serial1)

9:13:19.676 -> ets Jun  8 2016 00:22:57
19:13:19.676 -> 
19:13:19.676 -> rst:0xc (SW_CPU_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
19:13:19.676 -> configsip: 0, SPIWP:0xee
19:13:19.676 -> clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
19:13:19.676 -> mode:DIO, clock div:1
19:13:19.676 -> load:0x3fff0018,len:4
19:13:19.676 -> load:0x3fff001c,len:1216
19:13:19.714 -> ho 0 tail 12 room 4
19:13:19.714 -> load:0x40078000,len:10944
19:13:19.714 -> load:0x40080400,len:6388
19:13:19.714 -> entry 0x400806b4
19:13:19.786 -> Yo! from serial UART 18/19
19:13:19.786 -> SbmDi⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮@D@⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮⸮
@%cGuru Meditation Error: Core  1 panic'ed (IllegalInstruction). Exception was unhandled.
19:13:19.823 -> Memory dump at 0x400e90f4: ffffffff ffffffff ffffffff
19:13:19.823 -> Core 1 register dump:
19:13:19.823 -> PC      : 0x400e90f8  PS      : 0x00060530  A0      : 0x800d1529  A1      : 0x3ffb1f80  
19:13:19.823 -> A2      : 0x3ffbfe88  A3      : 0x3ffbfe6c  A4      : 0x0001c200  A5      : 0x0800001c  
19:13:19.823 -> A6      : 0x00004e20  A7      : 0x00000000  A8      : 0x800d0c4f  A9      : 0x3ffb1f60  
19:13:19.857 -> A10     : 0x3ffbfe6c  A11     : 0x3f40013b  A12     : 0x0800001c  A13     : 0x00000009  
19:13:19.857 -> A14     : 0x00000009  A15     : 0x00000000  SAR     : 0x00000016  EXCCAUSE: 0x00000000  
19:13:19.857 -> EXCVADDR: 0x00000000  LBEG    : 0x400014fd  LEND    : 0x4000150d  LCOUNT  : 0xffffffbd  
19:13:19.857 -> 
19:13:19.857 -> ELF file SHA256: 0000000000000000
19:13:19.857 -> 
19:13:19.857 -> Backtrace: 0x400e90f8:0x3ffb1f80 0x400d1526:0x3ffb1fb0 0x400860ed:0x3ffb1fd0
19:13:19.891 -> 
19:13:19.891 -> Rebooting...

Here's my code:

#include <Arduino.h>

#define SbmDisplaySerial Serial1

void setup() {
  Serial.begin(115200);
  //Serial.setDebugOutput(true);
  Serial.println("Yo v0.0.1! from serial UART 18/19");

  SbmDisplaySerial.begin(9600, SERIAL_8N1);//, 16, 17);


  Serial.print("SbmDisplaySerial is ");
  Serial.println(SbmDisplaySerial);
}

int _loop = 1;

void loop() {
  // put your main code here, to run repeatedly:
  Serial.print("Loop #"); Serial.println(_loop++);
  delay(1000);

  if (!SbmDisplaySerial.available()) {
    delay(2000);
    Serial.println("No byte avail from the UART, looping…");
    return;
  }


   int b = 0;

   Serial.print("Synching with message limit (waiting for 0xA5 (165) header byte): ");
   int i=0;
   do {
     delay(10);
     b = SbmDisplaySerial.read();
     Serial.print(b);  
     Serial.print(" ");
     if (i%128==0) Serial.println();  
      i++;
   }
   while(b!=0xa5);

  Serial.println("Ok, packet started!");
  Serial.print("Received bytes: ");
  Serial.print(b);
  Serial.print(" ");

  int soc = 0;
  int voltage = 0;
  int current = 0;
  int capacity = 0;

  for(int i=1; i<16; i++) {   
    b = SbmDisplaySerial.read()&0xff;

    Serial.print(b);
    Serial.print(" ");

    switch(i) {
      case  0: Serial.print("Header byte 0xA5"); 
        voltage = 0;
        current = 0;
        capacity = 0;
      break;
      case  1: soc = b; Serial.print("(SoC: ");  Serial.print(soc); Serial.print("%) "); break;
      
      case  2: voltage = b<<8; break;
      case  3: voltage |= b;  Serial.print("(");  Serial.print(float(voltage)*0.01); Serial.print("V) "); break;
      
      case  4: capacity = b<<24; break;
      case  5: capacity = b<<16; break;
      case  6: capacity = b<<8; break;
      case  7: capacity |= b;  Serial.print("(");  Serial.print(float(capacity)*0.001); Serial.print("A.h) "); break;
      
      case  8: current = b<<24; break;
      case  9: current = b<<16; break;
      case 10: current = b<<8; break;
      case 11: current |= b;  Serial.print("(");  Serial.print(float(current)*0.001); Serial.print("A) "); break;
      
      //case 12: current = b<<8; break;
      //case 13: current = b<<8; break;
      //case 10: current |= b;  Serial.print("(TOA: ");  Serial.print(float(current)*0.001); Serial.print("Seconds) "); break;
    }
    

    if (!SbmDisplaySerial.available()){
      delay(2000);
      Serial.print(" No more byte prior reaching 16 bytes, looping…");

      break;
    }
  }

  Serial.println("Waiting for next packet");
  delay(10000);
  
}

[UPDATE] When ran on Arduino, I get typical logs as follows:

11:20:18.217 -> Yo v0.0.1! from serial UART 18/19
11:20:18.217 -> SbmDisplaySerial is 1
11:20:18.217 -> Loop #1
11:20:19.204 -> Synching with message limit (waiting for 0xA5 (165) header byte): 0 
11:20:19.204 -> 0 0 0 0 165 Ok, packet started!
11:20:19.275 -> Received bytes: 165 28 (SoC: 28%) 4 251 (12.75V) 0 0 54 248 (14.07A.h) 255 255 0 0 (0.00A) 0 0 0 0 Waiting for next packet
11:20:29.263 -> Loop #2
11:20:30.266 -> Synching with message limit (waiting for 0xA5 (165) header byte): 0 
11:20:30.266 -> 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 165 Ok, packet started!
11:20:30.508 -> Received bytes: 165 28 (SoC: 28%) 4 251 (12.75V) 0 0 182 0 (46.59A.h) 0 0 0 0 (0.00A) 0 0 0 0 Waiting for next packet

5
  • 2
    Serial.println(SbmDisplaySerial); how is that supposed to work?
    – StarCat
    Oct 12 '21 at 20:45
  • You simply read: "10:46:23.574 -> SbmDisplaySerial is 1" but you can ignoire, it's pure logging message. Oct 13 '21 at 8:48
  • The problem is that SbmDisplaySerial (or any Arduino Serial object) is not equal to "1", but an object with all kinds of properties that you can't simply "print". I don't know why the Arduino (AVR) allows this, but the Serial implementation of the ESP32 might not handle this gracefully. Why don't you try leaving this Serial.println() statement out and see if it makes a difference?
    – StarCat
    Oct 13 '21 at 12:28
  • FYI, I've tried your code on my own ESP32 and it does not crash. What Arduino IDE and ESP32 Core version are you using?
    – StarCat
    Oct 13 '21 at 12:38
  • @StarCat This is used to know the state of the connection (see arduino.cc/reference/en/language/functions/communication/serial/…). And anyway, If I remove it it makes no change to the game. Oct 14 '21 at 8:28
1

Here is what I've ended up with: I dropped Serial1 as I did not find anyway to make it run and I switched to Serial2, where everything works as expected.

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