ESP32-WROVER randomly goes into download mode (ROM serial bootloader for esptool.py)

[karlito]

Once in a while (2-3% of the time), the ESP32-WROVER will go into download mode even when GPIO0 is high. This happens after power cycling. We get the message below and we don't know what “boot:0x20” exactly means. We couldn’t find any useful documentation on the first stage bootloader.

Entire boot message:
rst:0x1 (POWERON_RESET),boot:0x20 (DOWNLOAD_BOOT(UART0/UART1/SDIO_FEI_FEO_V2))
waiting for download

For comparison purposes, when we actually want to enter download mode by setting GPIO0 low, the boot message is:

rst:0x1 (POWERON_RESET),boot:0x23 (DOWNLOAD_BOOT(UART0/UART1/SDIO_REI_REO_V2))
waiting for download

Thanks in advance.

[WiFive]

GPIO strapping results: Bit5-bit0 of boot_sel_chip[5:0] correspond to MTDI, GPIO0, GPIO2, GPIO4, MTDO, GPIO5, respectively.

So 0x20 is showing gpio0 as low

[ESP_Angus]

Hi Karlito,

Is your WROVER on a custom board? Does GPIO0 have any external pullup or other external connection? Is it possible the rise time of the GPIO0 pullup is slower than the rise time of the ESP32-WROVER's VCC?

Thanks,

Angus

[karlito]

Thanks for the answers.

It is a WROVER custom board. We used an external pullup resistor and we removed it. It seems to fix the issue since it never happens again after that.