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#51

A20 / Re: HDMI connection back feedi...

Last post by LubOlimex - March 05, 2026, 10:23:42 AM

Latest that we sell, I got it from the shop. Revision N it is. But this part of the circuit hasn't been changed like forever. It is something else, probably some option in the monitor or the monitor itself (HDMI CEC) or maybe the monitor is not properly grounded... Maybe try powering the monitor from another outlet that is properly grounded. But it can be an issue with the monitor itself. Some monitors are not grounded. We published this article 12 years ago:

https://olimex.wordpress.com/2014/01/22/bevare-non-grounded-tv-monitors-can-damage-your-olinuxino/

Maybe try the FUSE workaround.

#52

A20 / Re: HDMI connection back feedi...

Last post by dry - March 05, 2026, 02:23:01 AM

Interesting, I have another DELL model U2715H, and that behaves same, still read 1.8V.

Tested by connecting to HDMI port from 2 different Lenovo laptops - bad test probably? ...one from 2017 model one from 2025, both then give me full 5V on same pins (with olimex not powered through own power).

Connected to my 65" Sony OLED tv, to one of its HDMI, and that is only time I didn't seem to see any voltage on the Olimex board, but I cannot confirm that HDMI would have worked at all with Sony TV - as I didn't get any test that port would work woth Olimex.

By the way, my Olinuxino-Micro is Rev.M board, I bought it some years back. Which version you tested?

Thanks for support

#53

ESP32 / Re: ESP32-C6 power supply

Last post by LubOlimex - March 04, 2026, 04:45:36 PM

Thank you for the update! Glad you got it sorted!

#54

ESP32 / Re: ESP32-C6 power supply

Last post by Partec - March 04, 2026, 03:33:05 PM

Sorry, It was a software problem.
Troubleshooting - No Boot: If the ESP32-C6 refuses to run code without a serial terminal connected, remove any while(!Serial); lines from your setup() function, as this waits for a connection that may not exist.
Now is OK

#55

ESP32 / Re: ESP32-C6 power supply

Last post by Partec - March 04, 2026, 02:34:16 PM

I use Arduino IDE version 2.3.5
Very simple software rele 1 on/off every 4 seg. code:

//Prueba placa OLIMEX ESP32-C6-EVB

// ====== PINES ======
const int inputPins[4] = {1, 2, 3, 15};      // Entradas
const int relayPins[4] = {10, 11, 22, 23};    // Relés


void setup() {
  Serial.begin(115200);
  while(!Serial) delay(10);

  for(int i=0;i<4;i++){
    pinMode(inputPins,INPUT_PULLUP);
    pinMode(relayPins,OUTPUT);
    digitalWrite(relayPins,LOW);
  }
  Serial.println("Termino el setup");

}

void loop() {
  digitalWrite(relayPins

• ,HIGH);

  Serial.println("rele HIGH");
  delay(4000);
  digitalWrite(relayPins

• ,LOW);

  Serial.println("rele LOW");
  delay(4000);
}


If I power it with USB or with USB and 12V, everything is OK, it works, and if I press the reset button, it restarts without a problem.

If I power it only with 12V (12V 5A power supply):
A) It continues to work if it was previously powered by USB. (I disconnect the USB while the 12V is still applied)

B) If I press the reset button, it doesn't start and doesn't work again.

C) From a powered-off state, with no power supply, I connect the 12V, and it doesn't start.

#56

A20 / Re: HDMI connection back feedi...

Last post by LubOlimex - March 04, 2026, 11:11:22 AM

I checked today with few HDMI monitors and displays here and it doesn't happen here. They don't feed power to the board. It is some sort of problem with your specific monitor.

I also tested something else, if the HDMI output would work if I remove the power pin (pin 18) of the HDMI - good news is that it works. Sadly I can't tell if that would fix the issue since our displays don't provide parasitic power.

So if you have some soldering skills - maybe try the same unsolder and remove FUSE1 (it is just below the HDMI connector at the bottom) on the +5V line of the HDMI and test again. If it doesn't solve the issue, solder it back.

#57

ESP32 / Re: ESP32-C6 power supply

Last post by LubOlimex - March 04, 2026, 08:45:33 AM

Give us more details about the software. How do you determine that it doesn't boot? Did you try with very simple code?

#58

A20 / Re: HDMI connection back feedi...

Last post by dry - March 04, 2026, 01:11:23 AM

Its a Dell business monitor, P2719HC says

#59

ESP32 / ESP32-C6 power supply

Last post by Partec - March 03, 2026, 08:36:45 PM

I have an ESP32-C6-EVB board. If I connect it to my computer via USB, it works perfectly; it loads and runs the software. But if I power it with only 12V, it continues to function even without the USB connection. The problem is that it won't boot if powered solely by 12V. Any suggestions? The 5v LED lights up in all cases.

#60

A20 / Re: HDMI connection back feedi...

Last post by LubOlimex - March 03, 2026, 04:50:23 PM

It will probably not lead to hardware failure but it is not very good, some hardware might be left at dubious levels when you power it for real.

Maybe it can be improved from the settings of the HDMI device like disable CEC mode or disable power link, for example.

You can also test with another HDMI equipment or first power the board before powering or attaching the HDMI device.

What is the monitor exactly?