ESP32 Forum

I have a board that I designed using the ESP32-C3 chip. I did not design in a USB-to-UART chip and have D+/D- (GPIO19/18) wired directly to the USB connector.

GPIO2 is pulled high with a 10k
GPIO8 is pulled high with a 10k
GPIO9 is pulled high is connected to a button that goes to GND when pressed

3.3V rail measures 3.3V
40MHz Oscillator is connected to XTAL_P

Windows 10 fails to enumerate the board (pressing the button while plugging in the USB cable) with an error message of "Device Descriptor Request Failed". I'm not sure if that means the ESP32-C# did not respond or if the reply was corrupt.

I have U0TXD/U0RXD connected to header and I tried to connect a FTDI board but could not see any messages on boot (what BAUD rate is used on the initial messages?

I thought I would post here to see if anyone has some helpful advice on how to find what the problem may be. I've inspected the board for soldering issues and don't see anything obviously wrong.

Thanks in advance for any help.

You should at least see the signon message on the Tx pin... if you don't the chip likely is not starting up correctly. That's either your power or your clock, although I can't tell you what exactly is wrong with those. (Not sure if we support piping a 40MHz clock directly into the ESP32C3 in the way you did it.)

Just so I can configure my terminal correctly what BAUD rate do these initial messages come through at? I remember that the ESP8266 has an initial rate of ~76kHz so I wanted to know if that was still the case.

I have yet to use a processor that did not accept an oscillator as the clock source. You can see it referenced in the Hardware Reference Manualhttps://www.espressif.com/sites/default ... nes_en.pdf, on page 10, Figure 7

I know the power rail is good but I do need to get the board connected to the scope and confirm there's 40MHz on the clock.

EDIT: Seems like there is a problem with the oscillator so I'll have to do some rework after the Holiday and see if I can get the clock going.

Good thing you found it. My remark was mostly based the fact that you were sending the output of the osc directly into the ESP32, from memory you needed something else in series, and indeed the datasheet mentions an inductor there. Everything from the ESP32 on will output its initial boot message at 115200 baud.

Yes, I do have a 0402 in series with the oscillator output before the ESP input. I've never had to use an inductor in another designs but if the ESP happens to be the odd MCU I'll be covered.

Thanks for confirming the initial BAUD is 115200, that will help eliminate one unknown once I replace the oscillator. This chip is still relatively new so there's not much information available for those of us "brave" enough to design in the chip instead of a module.

I'll report back once the oscillator is replaced just to close the loop on this post.

I was able to replace the oscillator and make some progress. The board enumerates on a Windows PC and I have been able to program the board using the Arduino 2.0 IDE but the boards seems to be in an endless loop. Hopefully someone can take a look and see if they can find some clues as to what my next problem is.

I made some additional progress and got some example code running. I saw on some other posts that you have to set "Flash Mode" from QIO to DIO. Doing that wasn't enough to get the code running properly but I changed "Core Debug Level" from the default None to Verbose and after that the code seemed to work as expected.

Programming the board always seems to take 2-3 tries so I'm not sure what's up with that but at least I'm making progress.

Is anyone else out there working on C3 projects?

Hey Georgeloak, you did a nice job, i would like to develop a custom board too, I'm going to use a bare C3 chip not a WROOM.

I'm going to use the embedded 4MB flash in the bare C3 and just 1 button to turn ON the C3, I won't use a reset button.

Can you explain me if I need to do the same thing as you did with the GPIO2,8 and 9?