No connection with diy emontx4


I recently started to build a new set of emontx4.

I finished to populate one board but I cannot manged to upload the firmware.
I tested with my emonsd pi or directly from the Arduino IDE and I’m always getting the same error:

avrdude-original: stk500_recv(): programmer is not responding

I have also checked the avr chip soldering with a microscope and everything looks correctly connected.

Any idea to help me with that?
Do I have maybe forgotten to do something before connecting de board?


Welcome, Alexandre, to the OEM forum.

OEM/Megni supplies the emonTx4 fully built and tested. If you have a bare printed circuit board and all the components, where did you get those from? Are you certain everything is exactly the same as the version from our factory?

You are the only person I have read about who has tried to do this, so it is not very likely that anyone else, the developers excepted, has experienced the same problem.

Are you aware that the USB-C connector on our emonTx4 is sensitive to the orientation?


I used the gerber archive for version 4.0.4 available on gitbhub and order the board from directly jlcpcb.

Yes I’m aware that the USB-C connector needs to be oriented in the right way.
The board is detected on the RPI or my computer as additional serial interface meaning that communication works a leat until the UART.

Hello @psykok well done building this yourself!

The first step with a new board and AVR-DB is to upload the bootloader using serial UDPI, see:

The serial UDPI programmer can be built with a standard USB UART programmer and an additional diode as described in the above guide, that produces a 3-pin UDPI interface.

The Arduino IDE has a Serial UDPI upload option.

Then with the bootloader in place you can upload firmware the usual way via the USB-C connection.

1 Like

Great, I will try that


Fixed, the board is working.

After uploading the bootloader everything went as described in the document.

Thanks for your help.

1 Like