What Causes 'Clock Stretch Too Long' Errors When Flashing ESP32?
Hey guys I'm experiencing intermittent timeouts and invalid packet errors while programming my ESP32-WROOM-32 module via USB using esptool version 2.8 and ESP-IDF version 4.4 for a cloud-connected IoT project integrating with AWS IoT Core. I've been trying to flash custom firmware, but the process consistently fails. Upon reviewing the error logs, I noticed the error message "timeout: clock stretch too long" followed by "invalid packet" errors. I've verified that the board is in boot mode by pulling GPIO0 low and confirmed the serial port configuration is set to 115200 baud. Despite trying different USB cables, adapters, and computers, issues persist. What are potential causes and troubleshooting steps to successfully flash the firmware and establish reliable cloud connectivity?
3 Replies
It may be power supply issue or USB connection instability, You can try to lower the baud rate for flashing and check if disabling Wi-Fi/Bluetooth during flashing helps. Also, try reducing the length of the USB cable or use shorter, high-quality ones to minimize interference.
@Daniel kalu in addition to this, the USB-to-UART bridge or its driver may have compatibility issues or malfunctions. Ensure that the CP210x or FTDI driver is installed correctly. Try using a different USB-to-UART adapter or updating the drivers on your system.
After lowering the baud rate and updating the CP210x driver to the latest version as @Dark AI mentioned I was able to successfully flash the firmware. The issue was indeed related to the USB-to-UART bridge compatibility.
Thanks for this guys 🙏