Cannot flash ESP32S3-DevKitC-1 over TX0/RX0 with ESP-Prog, only Prolific USB-TTL (ESPTOOL-1203)

[zfields]

Operating System

Ubuntu 24.04

Esptool Version

v4.8.1 - v5.1.0

Python Version

Python 3.12.3

Chip Description

ESP32-S3-WROOM-1

Device Description

ESP32S3-DevKitC-1, connected to a USB to TTL, powered via USB (not UART) connector.
Both the DevKit and the USB to TTL connected directly to laptop's USB.

Hardware Configuration

[SUCCESS] Prolific USB-TTL connected to (GND/TX0/RX0)

[FAIL] ESP-Prog connected to (GND/TX0/RX0)

[FAIL] FTDI USB-TTL connected to (GND/TX0/RX0)

How is Esptool Run

Arduino esp32 BSP v3.3.2

Full Esptool Command Line that Was Run

/home/zak/.arduino15/packages/esp32/tools/esptool_py/5.1.0/esptool --chip esp32s3 elf2image --flash-mode dio --flash-freq 80m --flash-size 4MB --elf-sha256-offset 0xb0 -o /home/zak/.cache/arduino/sketches/79DD62760C5463CDB84482C524C384A8/Blink.ino.bin /home/zak/.cache/arduino/sketches/79DD62760C5463CDB84482C524C384A8/Blink.ino.elf

Esptool Output

esptool v5.1.0
Creating ESP32S3 image...
Merged 2 ELF sections.
Successfully created ESP32S3 image.
python3 /home/zak/.arduino15/packages/esp32/hardware/esp32/3.3.2/tools/gen_esp32part.py -q /home/zak/.cache/arduino/sketches/79DD62760C5463CDB84482C524C384A8/partitions.csv /home/zak/.cache/arduino/sketches/79DD62760C5463CDB84482C524C384A8/Blink.ino.partitions.bin
/usr/bin/env bash -c "[ ! -d \"/home/zak/.cache/arduino/sketches/79DD62760C5463CDB84482C524C384A8\"/libraries/Insights ] || python3 \"/home/zak/.arduino15/packages/esp32/hardware/esp32/3.3.2\"/tools/gen_insights_package.py /home/zak/.cache/arduino/sketches/79DD62760C5463CDB84482C524C384A8 Blink.ino \"/tmp/.arduinoIDE-unsaved2025919-376587-12vls2l.vog5/Blink\""
/usr/bin/env bash -c "[ ! -d \"/home/zak/.cache/arduino/sketches/79DD62760C5463CDB84482C524C384A8\"/libraries/ESP_SR ] || [ ! -f \"/home/zak/.arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.5-07e9bf49-v1/esp32s3\"/esp_sr/srmodels.bin ] || cp -f \"/home/zak/.arduino15/packages/esp32/tools/esp32-arduino-libs/idf-release_v5.5-07e9bf49-v1/esp32s3\"/esp_sr/srmodels.bin \"/home/zak/.cache/arduino/sketches/79DD62760C5463CDB84482C524C384A8\"/srmodels.bin"
/home/zak/.arduino15/packages/esp32/tools/esptool_py/5.1.0/esptool --chip esp32s3 merge-bin -o /home/zak/.cache/arduino/sketches/79DD62760C5463CDB84482C524C384A8/Blink.ino.merged.bin --pad-to-size 4MB --flash-mode keep --flash-freq keep --flash-size keep 0x0 /home/zak/.cache/arduino/sketches/79DD62760C5463CDB84482C524C384A8/Blink.ino.bootloader.bin 0x8000 /home/zak/.cache/arduino/sketches/79DD62760C5463CDB84482C524C384A8/Blink.ino.partitions.bin 0xe000 /home/zak/.arduino15/packages/esp32/hardware/esp32/3.3.2/tools/partitions/boot_app0.bin 0x10000 /home/zak/.cache/arduino/sketches/79DD62760C5463CDB84482C524C384A8/Blink.ino.bin
esptool v5.1.0
Wrote 0x400000 bytes to file '/home/zak/.cache/arduino/sketches/79DD62760C5463CDB84482C524C384A8/Blink.ino.merged.bin', ready to flash to offset 0x0.
/home/zak/.arduino15/packages/esp32/tools/esp-x32/2507/bin/xtensa-esp32s3-elf-size -A /home/zak/.cache/arduino/sketches/79DD62760C5463CDB84482C524C384A8/Blink.ino.elf
Sketch uses 302323 bytes (23%) of program storage space. Maximum is 1310720 bytes.
Global variables use 20648 bytes (6%) of dynamic memory, leaving 307032 bytes for local variables. Maximum is 327680 bytes.
"/home/zak/.arduino15/packages/esp32/tools/esptool_py/5.1.0/esptool" --chip esp32s3 --port "/dev/ttyUSB0" --baud 921600  --before default-reset --after hard-reset write-flash  -z --flash-mode keep --flash-freq keep --flash-size keep 0x0 "/home/zak/.cache/arduino/sketches/79DD62760C5463CDB84482C524C384A8/Blink.ino.bootloader.bin" 0x8000 "/home/zak/.cache/arduino/sketches/79DD62760C5463CDB84482C524C384A8/Blink.ino.partitions.bin" 0xe000 "/home/zak/.arduino15/packages/esp32/hardware/esp32/3.3.2/tools/partitions/boot_app0.bin" 0x10000 "/home/zak/.cache/arduino/sketches/79DD62760C5463CDB84482C524C384A8/Blink.ino.bin" 
esptool v5.1.0
Serial port /dev/ttyUSB0:
Connecting......................................
A fatal error occurred: Failed to connect to ESP32-S3: No serial data received.
For troubleshooting steps visit: https://docs.espressif.com/projects/esptool/en/latest/troubleshooting.html

Failed uploading: uploading error: exit status 2

More Information

Looking at an oscilloscope captures (attached), it appears the FTDI and ESP-Prog are unable to drive the UART close enough to GND to be recognized by the DevKit.

Alternatively, the Prolific USB to TTL is able to drive the line to 1V, which seems to cross the dead zone just enough to work.

---

This has been tested on multiple laptops, multiple DevKits, multiple major versions of the Arduino IDE (v1 and v2), multiple major versions of esptool (both v4 and v5).

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This has been tested with and without a USB isolator inline with the FTDI (it makes no difference).

Other Steps to Reproduce

• Power the DevKit with the USB usb port.
• Connect to GND, TX0, and RX0.
• Enter the bootloader by manually pressing BOOT, pressing RESET, releasing RESET, and releasing BOOT.
• Flash "Blink" using Arduino IDE.

I Have Read the Troubleshooting Guide

• I confirm I have read the troubleshooting guide.

[github-actions]

Hi @zfields! Please be aware that (1) the following suggestions are generated by a bot and haven't been fact-checked by Espressif Systems, (2) burning eFuses and enabling security features are irreversible operations and can damage your ESP32 device. We hope that this message will help you until an Espressif Engineer looks at your issue.

---

Based on the information provided and the Espressif documentation, here are some key points and troubleshooting steps relevant to your issue:

1. "No serial data received" Error

The error message from esptool (Failed to connect to ESP32-S3: No serial data received.) typically indicates a hardware-level issue with the UART connection. According to Espressif's documentation, this can be due to:

• RX/TX serial lines not being connected properly.
• The hardware not working at all.
• Problems with resetting into download mode (bootloader mode) [ESP32-S3 Common Errors].

2. Manual Bootloader Mode Entry

You are already manually entering the bootloader mode by holding BOOT, pressing RESET, releasing RESET, and then releasing BOOT, which is the correct procedure for boards that do not support automatic reset [ESP32-S3 Flashing Troubleshooting].

3. UART Voltage Levels

The documentation does not specifically address issues with certain USB-to-UART adapters not being able to drive the lines low enough for the ESP32-S3 to recognize, but it does emphasize that only 3.3V UART levels are supported—5V or RS-232 levels must not be used [ESP32-S3 Serial Connection].

4. Other Common Causes

• Bad quality USB cable or breadboard issues can cause serial noise or corruption.
• Insufficient power supply can also cause flashing issues, especially if the USB-to-UART adapter cannot provide enough current [ESP32-S3 Common Errors].

5. Recommendations

• Double-check the wiring: TX on the ESP32-S3 should go to RX on the adapter, and RX to TX.
• Ensure you are using a high-quality USB cable and a reliable power source.
• Try lowering the baud rate (e.g., esptool --baud 9600 ...) to see if communication improves.
• If possible, try removing the board from any breadboard to avoid shorts.
• If the issue persists only with certain adapters (like ESP-Prog or FTDI), but works with Prolific, it may be due to the electrical characteristics of those adapters. The documentation does not provide a direct solution for this, but it is consistent with your oscilloscope findings.

6. Summary

Your approach and troubleshooting steps align with Espressif's official recommendations. The fact that the Prolific adapter works, but ESP-Prog and FTDI do not, suggests a hardware-level compatibility issue with the voltage levels or drive strength of those adapters. The Espressif documentation does not provide a specific workaround for this scenario, but confirms that such hardware-level issues can cause the "no serial data received" error.

If you continue to experience issues, Espressif recommends opening an issue for further support, as you have already done [ESP32-S3 Common Errors].

---

References integrated above as per Espressif documentation. If you need further assistance, please provide additional details or contact Espressif support.

[sidwarkd]

I was able to reproduce this behavior with an ESP-Prog and S3 Devkit C1 version 1.0 as well. I was never able to get the dev kit to flash using the ESP-Prog. I was trying different orientations of the RX/TX pins just to make sure I didn't have them swapped and the closest I got to having it work generated the following error.

Failed to connect to Espressif device: Download mode successfully detected, but getting no sync reply: The serial TX path seems to be down.

When I got that error I swapped the RX/TX pins and then got the message reported by @zfields of:

Failed to connect to Espressif device: No serial data received.

[Dzarda7]

Hello @zfields and @sidwarkd, yes, this might be an issue, because other USB-UART converter (CP2102) on the board tries to hold the RX path of the target high. I encountered it even with ESP-Prog2 where I solved it by setting the driving current of TX (TX of the ESP-Prog2, so RX of the target) to 40mA (found that 30mA is enough for it to reliably work).

I believe you encountered the same issue. There is nothing I believe we can do on esptool side. But there might be option for you. I noticed that ESP-Prog uses FT2232HL and the second @zfields tested is most probably FT232RL. I found in the datasheet of the chips that they can supply around 16mA (might be configurable), but they also have some High Current I/Os option.

So I suggest you trying to download FT_PROG utility and try to set the current higher if that is possible and try to set the High Current I/Os option for the pins. Hopefully this will help.

[zfields]

oof.

Thank you @sidwarkd and @Dzarda7. I was thinking I was going crazy at first.

@Dzarda7, I didn't know there was an ESP-Prog2. Does it work out of the box, or did you need to use FT_PROG to dial up the current?

[Dzarda7]

@zfields ESP-Prog2 is based on ESP32-S3 instead of the FT2232HL. It comes pre-flashed and should work out of the box, especially this issue is resolved there, I work with that a few times a week and did not encounter an issue.

But if you will there is a firmware for that esp-usb-bridge, there is also a link at the bottom of the webpage to flash the latest release from the browser. And in case of an issue, you can open it on github, I will respond ASAP 😄.

[sidwarkd]

@Dzarda7 Thanks so much for the info. I just ordered a couple of the ESP-PROG-2s so I can confirm the behavior you mention. In your original response you said:

I encountered it even with ESP-Prog2 where I solved it by setting the driving current of TX (TX of the ESP-Prog2, so RX of the target) to 40mA (found that 30mA is enough for it to reliably work).

How do I change that setting once I have the PROG-2 devices?

[Dzarda7]

@sidwarkd It should be by default set to 40mA, if it is not, update the firmware using ESP Launchpad at the bottom of esp-usb-bridge github, or flash it as normal ESP-IDF app. But as I said, I recommend also playing a bit with FT_PROG utility.

[Dzarda7]

btw @sidwarkd @zfields, you can try esp-usb-bridge with any ESP32-S3 devkit, only you have to compile it yourself and change the pinout.