esptool-ftdi.py

Overview

This esptool.py wrapper lets you use RTS/CTS for ESP8266/ESP32 chip resets instead of the usual RTS/DTR. It only works with FTDI-based USB to serial adapters.

Normally, CTS is an input. On FTDI chips, CTS can be reconfigured as an output by entering bitbang mode. This wrapper replaces all of the internal esptool.py serial routines with direct calls into libftdi1 and libusb-1.0 to dynamically switch between normal and bitbang modes as needed to make the typical reset-into-bootloader sequence work.

Hardware connections

FTDI	ESP32
GND	GND
VIO	3V3
RX	U0TXD
TX	U0RXD
RTS	EN (CHP_PU)
CTS	BOOT (GPIO0)

Requirements

• libftdi1 1.4
• libusb 1.0

This was tested on Linux and macOS. For other OSes, changes to the low level USB access may be needed.

Usage

$ ./esptool-ftdi.py
usage: ./esptool-ftdi.py <path-to-esptool.py> [args...]

To use it, prepend esptool-ftdi.py to your existing esptool command line. For example, instead of:

$ esptool.py chip_id
esptool.py v2.3.1
Connecting........_____....._____....._____....._____....._____....._____....._____....._____....._____....._____

A fatal error occurred: Failed to connect to Espressif device: Timed out waiting for packet header
$

run this and be much happier:

$ ./esptool-ftdi.py esptool.py chip_id
esptool-ftdi.py wrapper
esptool.py v2.3.1
/dev/ttyUSB0 is at bus 3 dev 78 interface 0
Connecting.....
Detecting chip type... ESP32
Chip is ESP32D0WDQ6 (revision (unknown 0xa))
Features: WiFi, BT, Dual Core, VRef calibration in efuse
Uploading stub...
Running stub...
Stub running...
Chip ID: 0xe2b4e62dac76
Hard resetting via RTS pin...
$

Integrating with ESP-IDF

For esp-idf v4.4 or later, you can set the ESPTOOL_WRAPPER environment variable to point to esptool-ftdi.py, and it will be invoked automatically. For example:

export ESPTOOL_WRAPPER=/path/to/esptool-ftdi.py
idf.py flash