Re: usb serial - need quirk?

From: Daniel Braniss <>
Date: Mon, 29 Nov 2021 07:39:52 UTC

> On 29 Nov 2021, at 09:24, Daniel O'Connor <> wrote:
>> 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)
i’ll try this ASAP, thanks

BTW, looking at the m5 stamp c3 diagram, I can’t see how the usb-typec is connected to the esp32c3
from the esp32c3 docs, it’s gpio9 that needs to be grounded to flash, and I don’t see that happening when
using the onboard usb.
oh well,
thanks again,

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