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I have built a custom circuit board using the ESP32-C3-MINI-1-H4 module (datasheet).

Here is a schematic:

enter image description here

I have the GND, Tx, and Rx lines hooked up to an Arduino Uno without the ATmega. The 3.3 V comes from an external power supply.

I have successfully put the chip into download mode (as shown from the serial output below).

ESP-ROM:esp32c3-api1-20210207

Build:Feb 7 2021

rst:0x1 (POWERON),boot:0x5 (DOWNLOAD(USB/UART0/1))

waiting for download

I attempted to upload an example sketch using the following settings (Arduino IDE).

Arduino Settings

I held down the reset button (S4) until the Rx light on the Uno started flashing.

It works about 5% of the time, but 95% of the time the TX light does not blink with the RX light and it ends in this:

A fatal error occurred: Failed to connect to ESP32-C3: No serial data received.

I'm not sure how that is possible, as the serial data appears on the oscilloscope, and it is clearly in download mode as shown by the serial output.

I have tried removing the voltage divider from the RX line, but that didn't help. Is there any way to make uploading more consistent?

jb0
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2 Answers2

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You must be in flash mode DIO and watch the "USB CDC on boot" which must be on if you use native C3 usb and off if you use an external usb-serial converter.

You can upload OK in QIO mode but program wont start, that is EXACTLY what OP is asking.

sempaiscuba
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Pepe The Frog
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The issue was with using the arduino as my USB to UART converter. Buying a CP2102 converter solved the issue.

jb0
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