ESP32 Forum

Hello,
I am currently developing a custom PCB for a hobby project and for that I used a Pico-D4 chip and a CP2104 serial chip. As you can see in the schematic, I used a common two-transistor auto boot sequence "selector" circuit for programming.

The problem is that I always get a "timed out waiting for packet header" error when I try to program it. I first thought that I have a faulty solder connection but after double checking, I concluded that everything is ok and I attempted to hook up my logic analyzer. As you can see in the data capture screenshot, in general I receive a low on IO0, followed by a low at RESET and then IO0 -> high and then RESET -> high.

If I trigger this sequence by hand via two jumper wires, I can program the chip but the automatic programming does not work.
Also the captured data looks really odd. You can download the whole saleae data file here: https://www4.zippyshare.com/v/o5px217q/file.html

Has someone an idea what the problem could be?

Thank you all in advance!!!

Hi GatCode,

Can you please try running "esptool.py --trace ...", or alternatively attach the UART TX pin to your logic analyzer? This will show what the chip is outputting after attempting to reset into bootloader mode.

Angus

Hi Angus,
thank you very much for your help!
I just tried both approaches and here are the two capture files:
https://www49.zippyshare.com/v/x9n46WcT/file.html (capture from upload with esptool)
https://www49.zippyshare.com/v/1m4UNLVd/file.html (capture from upload with Arduino IDE)

also I attached the log of the esptool command you suggested.
In the logic captures, it looks like that there is no signal present on the TX line, despite correct wiring and soldering, I also took a capture on the CH2104 pin directly.

Hi GatCode,

No output at all from the chip is weird. Any time the EN pin on the PICO-D4 goes from low to high there should be some serial output of some kind, even if it doesn't boot into the right mode.

The first trace you posted shows a weird oscillation on the rising edge of RES. Is it possible the pullup resistor R5 has a soldering issue or is pulling to the wrong power rail? If you look at this signal on an oscilloscope, what do you see?


Angus

Hi Angus,

thank you for your answer, I just switched out the R5 and rechecked all pins on the ESP32 since I have no access to an oscilloscope.

As you told, I am getting a response from the ESP32 but nevertheless, still the same problem at upload.

In the image below you can see what I mean (all measurements are taken directly on the ESP32 pins - hence the names)
Also here is the capture file: https://www10.zippyshare.com/v/3NtbkbaY/file.html

Is it normal that the chip answers so little?

Thank you very much!

In the meantime I tried all possible combinations of different auto boot circuits but always the same result. Can someone help me out?