Re: usb serial - need quirk?

From: Daniel O'Connor via hackers <>
Date: Mon, 29 Nov 2021 07:24:20 UTC

> On 29 Nov 2021, at 17:35, Daniel Braniss <> wrote:
>>> it’s the last line that I think is causing failure to flash the device (probably needs the break to set the speed?)
>> Why would it need break to set the speed?
> don’t know, but I’ve seen in the past serial stuff that needed the break to synchronize.
>>> any ways, is there some fix for this?
>> You didn't actually post the problem you are having so it's impossible to say :)
>> I assume esptool fails but it would be helpful if you posted the output.
> the flashing  keeps failing with:
> Chip is ESP32-C3 (revision 3)
> Features: Wi-Fi
> Crystal is 40MHz
> MAC: 7c:df:a1:a3:61:74
> Uploading stub...
> A fatal error occurred: Failed to write to target RAM (result was 01070000)
>> I haven't used an ESP32-C3 but all of the other ESP's don't have USB built in so it depends what USB UART you have on your board - any idea which one it it?
> all the other esp32 I have work fine, it’s this esp32c3 that fails.
> anyways, i got hold of a ttl to usb from m5stack, and after some fiddling got it to flash!
> this chip is CP2104,
> so the problem seems to be in the driver for the unknown chip on this esp32c3 - no
> indication in the diagrams, nor can I read the micro words on the chip :-(

I had a look at the ESP32-C3 datasheet and it *does* have a USB interface built in and it talks about a CDC-ACM virtual serial port which matches what you see.

The only ACM quirk I can see is UQ_ASSUME_CM_OVER_DATA so you could try that I suppose..
(See the usb_quirk man page)

Daniel O'Connor
"The nice thing about standards is that there
are so many of them to choose from."
 -- Andrew Tanenbaum