ESP32C3 - UART flashing issue (restarting? - loop)

[Marcin Woz]

Hi,
I am struggling with ESP32-C3-mini-1 flashing issue.
According to datasheet power-up sequence for boot uart flashing looks correct:
1) IO8 - high, IO9 low, IO2 - high (not necessary)
2) Delay 10 ms
3) PWR-UP 3.3V
4) Enable pulled to 3.3V via 10k resistor with 100nF delay capacitor.

Anyway I am not able to flash chip. Instead I obtained some loop in log:

Code: Select all

[19:05:50:673] ESP-ROM:esp32c3-api1-20210207␍␊
[19:05:50:673] Build:Feb  7 2021␍␊
[19:05:50:673] rst:0x3 (RTC_SW_SYS_RST),boot:0x5 (DOWNLOAD(USB/UART0/1))␍␊
[19:05:50:673] Saved PC:0x40048b82␍␊
[19:05:50:718] Download boot modes disabled␍␊
[19:05:50:718] ESP-ROM:esp32c3-api1-20210207␍␊
[19:05:50:718] Build:Feb  7 2021␍␊
[19:05:50:718] rst:0x3 (RTC_SW_SYS_RST),boot:0x5 (DOWNLOAD(USB/UART0/1))␍␊
[19:05:50:718] Saved PC:0x40048b82␍␊
[19:05:50:718] Download boot modes disabled␍␊

Power supply 3.3V looks clear without any glitches.
Any ideas what can be wrong or what can be checked?

Thank you.

[ESP_Sprite]

[19:05:50:718] Download boot modes disabled␍␊

That's caused by a blown eFuse, usually blown in the process of enabling SecureBoot; it's not reversible I'm afraid. I assume you didn't do that yourself? If not, can you get me a picture of the module with the QR code readable? (I suspect it's a leftover module preprogrammed by some company that someone intercepted and sold on the open market.)

[Marcin Woz]

I did not use any commands related to eFuse.
The module have been bought from one of the biggest distributor of electronic components it was on cut tape. Unlikely it is reused.

Anyway, I attached photo.

[ESP_Sprite]

Ah, that is a different thing; this one is on the public market after all. That is an ESP32-C3-MINI-1-N4-A module. It's preflashed with firmware for AWS IoT ExpressLink and has SecureBoot enabled, which also disables download modes.