CircuitPython on Espressif SoCs

This port adds the Espressif line of SoCs to CircuitPython.

Support Status:

SoC

Status

ESP

beta

ESP32-C3

beta

ESP32-S2

stable

ESP32-S3

beta

How this port is organized:

  • bindings/ contains some required bindings to the ESP-IDF for exceptions and memory.

  • boards/ contains the configuration files for each development board and breakout available on the port.

  • common-hal/ contains the port-specific module implementations, used by shared-module and shared-bindings.

  • esp-idf/ contains the Espressif IoT Development Framework installation, including all the drivers for the port.

  • peripherals/ contains peripheral setup files and peripheral mapping information, sorted by family and sub-variant. Most files in this directory can be generated with the python scripts in tools/.

  • supervisor/ contains port-specific implementations of internal flash, serial and USB, as well as the port.c file, which initializes the port at startup.

  • tools/ includes useful Python scripts for debugging and other purposes.

At the root level, refer to mpconfigboard.h and mpconfigport.mk for port specific settings and a list of enabled CircuitPython modules.

Connecting to the ESP32

The ESP32 chip itself has no USB support. On many boards there is a USB-serial adapter chip, such as a CP2102N, CP2104 or CH9102F, usually connected to the ESP32 TXD0 (GPIO1)and RXD0 (GPIO3) pins, for access to the bootloader. CircuitPython also uses this serial channel for the REPL.

Connecting to the ESP32-C3

USB Connection:

On ESP32-C3 REV3 chips, a USB Serial/JTAG Controller is available. Note: This USB connection cannot be used for a CIRCUITPY drive.

Depending on the board you have, the USB port may or may not be connected to native USB.

The following connections need to be made if native USB isn’t available on the USB port:

GPIO

USB

19

D+ (green)

18

D- (white)

GND

GND (black)

5V

5V (red)

Connect these pins using a USB adapter or breakout cable.

UART Connection:

A USB to UART convertor can be used for connecting to ESP32-C3 to get access to the serial console and REPL and for flashing CircuitPython.

The following connections need to be made in this case:

GPIO

UART

21

RX

20

TX

GND

GND

5V

5V

BLE Connection:

This feature is not yet available and currently under development.

Connecting to the ESP32-S2

USB Connection:

Depending on the board you have, the USB port may or may not be connected to native USB.

The following connections need to be made if native USB isn’t available on the USB port:

GPIO

USB

20

D+ (green)

19

D- (white)

GND

GND (black)

5V

5V (red)

Connect these pins using a USB adapter or breakout cable to access the CircuitPython drive.

UART Connection:

A USB to UART convertor can be used for connecting to ESP32-S2 to get access to the serial console and REPL and for flashing CircuitPython.

The following connections need to be made in this case:

GPIO

UART

43

RX

44

TX

GND

GND

5V

5V

BLE Connection:

This feature isn’t available on ESP32-S2.

Connecting to the ESP32-S3

USB Connection:

Depending on the board you have, the USB port may or may not be connected to native USB.

The following connections need to be made if native USB isn’t available on the USB port:

GPIO

USB

20

D+ (green)

19

D- (white)

GND

GND (black)

5V

5V (red)

Connect these pins using a USB adapter or breakout cable to access the CircuitPython drive.

UART Connection:

A USB to UART convertor can be used for connecting to ESP32-S3 to get access to the serial console and REPL and for flashing CircuitPython.

The following connections need to be made in this case:

GPIO

UART

43

RX

44

TX

GND

GND

5V

5V

BLE Connection:

This feature is not yet available and currently under development.

Building and flashing

Before building or flashing the, you must install the ESP-IDF.

Note: This must be re-done every time the ESP-IDF is updated, but not every time you build.

Run cd ports/espressif from circuitpython/ to move to the espressif port root, and run:

./esp-idf/install.sh

After this initial installation, you must add the ESP-IDF tools to your path.

Note: This must be re-done every time you open a new shell environment for building or flashing.

Run cd ports/espressif from circuitpython/ to move to the espressif port root, and run:

./esp-idf/export.sh

When CircuitPython updates the ESP-IDF to a new release, you may need to run this installation process again. The exact commands used may also vary based on your shell environment.

Building boards is typically done through make BOARD=board_id. The default port is tty.SLAB_USBtoUART, which will only work on certain Mac setups. On most machines, both Mac and Linux, you will need to set the port yourself by running ls /dev/tty.usb* and selecting the one that only appears when your development board is plugged in. An example make command with the port setting is as follows:

make BOARD=board_id PORT=/dev/tty.usbserial-1421120 flash

board_id is the unique board identifier in CircuitPython. It is the same as the name of the board in the boards directory.

Debugging

TODO: Add documentation for ESP32-C3/S3 JTAG feature.

The ESP32-S2 supports JTAG debugging over OpenOCD using a JLink or other probe hardware. The official tutorials can be found on the Espressif website here, but they are mostly for the ESP32-S2 Kaluga, which has built-in debugging.

OpenOCD is automatically installed and added to your bash environment during the ESP-IDF installation and setup process. You can double check that it is installed by using openocd --version, as per the tutorial. Attach the JTAG probe pins according to the instructions for JTAG debugging on boards that do not contain an integrated debugger.

Once the debugger is connected physically, you must run OpenOCD with attached configuration files specifying the interface (your debugger probe) and either a target or a board (targets are for SoCs only, and can be used when a full board configuration file doesn’t exist). You can find the location of these files by checking the OPENOCD_SCRIPTS environmental variable by running echo $OPENOCD_SCRIPTS. Interfaces will be in the interface/ directory, and targets and boards in the target/ and board/ directories, respectively.

Note: Unfortunately, there are no board files for the esp32-s2 other than the Kaluga, and the included target/esp32s2.cfg target file will not work by default on the JLink for boards like the Saola 1, as the default speed is incorrect. In addition, these files are covered under the GPL and cannot be included in CircuitPython. Thus, you must make a copy of the esp32s2.cfg file yourself and add the following line manually, under transport select jtag at the start of the file:

adapter_khz 1000

Once this is complete, your final OpenOCD command may look something like this:

openocd -f interface/jlink.cfg -f SOMEPATH/copied-esp32s2-saola-1.cfg

Where SOMEPATH is the location of your copied configuration file (this can be placed in the port/boards directory with a prefix to ignore it with .gitignore, for instance). Interface, target and board config files sourced from Espressif only need their paths from the $OPENOCD_SCRIPTS location, you don’t need to include their full path. Once OpenOCD is running, connect to GDB with:

xtensa-esp32s2-elf-gdb build-espressif_saola_1_wrover/firmware.elf

And follow the Espressif GDB tutorial instructions for connecting, or add them to your gdbinit:

target remote :3333
set remote hardware-watchpoint-limit 2
mon reset halt
flushregs
thb app_main
c