Sketch uploads to ESP32-S3R8N16 successfully but when the ESP reboots, the sketch does not run

Other Hardware 3rd Party Boards
1

I have an ESP32-S3R8N16 that I have programed with the following simple sketch.

const int intLEDpin = 41;
void setup() {
  Serial.begin(19200); // Starts the serial communication
  delay(1000);
  while (!Serial);
  Serial.println("Starting setup!");
  pinMode(intLEDpin, OUTPUT);

  // Serial.println("Finished with setup!");
}

void loop() {
  Serial.println("on!");
  digitalWrite(intLEDpin, HIGH);
  delay(500);
  Serial.println("off!");
  digitalWrite(intLEDpin, LOW);
  delay(500);
}

Works without an issue when I connect the ESP32 to my computer and upload the sketch to the ESP32.

But when I disconnect the ESP32 and try to power it externally with a 5v power supply it does not work.

So I connect the ESP32 back to my PC and the sketch does not run. I can then upload the sketch again and it will run without any issues. Again, when I disconnect and from my PC and then reconnect it to my PC the sketch will not run.

If I run a similar sketch on an ESP-WROOM-32 and reboot it, power it externally, the sketch works without any issues.

What am I missing here with my ESP32-S3? Am I doing something wrong? Is there something wrong with this MCU? Help! I am losing my mind!

2

That is because the following line is waiting for the serial connection to the PC to be established.

  while (!Serial);

It is a very common mistake, and one possibility is to replace that line with something like delay(2000); (otherwise you may miss the first few lines of Serial.print() output when connected to the PC).

3

That was exactly it and after thinking about it, it sure does make sense. The program halts when there is no serial connection.

Now I wish I could get the past few hours of my life.

Thank you so much for your quick response.

Wait...why does the ESP-WROOM-32 work without an issue? Is it just because it is a different MCU and this functions in a different manner?

4

I've never heard of such an exception, but if Espressif Corp. built one in to their Arduino support package, fine.

5

The problem only manifests itself on boards with native USB; that is, boards where the main processor provides the USB functionality for communication with the PC.

If the ESP-WROOM-32 board has a serial-to-usb converter (CP210x, CH34x, ...), the USB communication is not provided by the main processor but by that converter.

Find a schematic for the ESP-WROOM-32 (I could not quickly find one) and check. The datasheet for the processor might also tell you.

1 Like
6

I have a similar board and use the following:

  unsigned long startTime = millis();
  while (!Serial && ((millis() - startTime) < 2000) ) {}

You can probably even drop the startTime since it will be close to zero after startup. The reason I need it is I invariably use the native USB to allow hardware debugging in IDE ver 2.

1 Like
7

I currently do not know what most of this means but I now have even more to research! Thank you for sharing and explaining!

8

The check on the elapsed time makes sense here and will certainly get me out of the infinite loop. Thank you!

9

That's life :rofl:

I do not know which operating system you're using.
For Windows

  1. Find the board in Windows device manager
  2. Right click, select properties (or something like that, not a Windows user at the moment).
  3. Select the details tab and from the drop down select hardware ids.

For Linux

  1. Disconnect the board.
  2. Run dmesg -w (the application will not close)
  3. Connect the board.
  4. Observe the changes.
  5. Close the dmesg using CTRL+C

For a CH341 you will see e.g.

[44432.487175] usb 1-5.1: New USB device found, idVendor=1a86, idProduct=7523, bcdDevice= 2.63

idVendor is the VID, idProduct is the PID. You can look those up on the web.

The information in Windows looks a little different (longer strings containing those numbers) but you should be able to find the numbers as mentioned above.

10

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