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SPI_setup.md

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Wi-Fi connectivity Setup over SPI

1. Setup

Supported Targets ESP32 ESP32-S2 ESP32-S3 ESP32-C2 ESP32-C3 ESP32-C6

1.1 Hardware Setup/Connections

  • In this setup, ESP board acts as a SPI peripheral and provides Wi-Fi capabilities to host. Please connect ESP board to STM32F469I board's CN12 Extension connecter with jumper cables as mentioned below. It may be good to use small length cables to ensure signal integrity.
  • STM32F469I should be powered with correct incoming power rating. ESP peripheral can be powered through PC using micro-USB/USB-C cable. STM32 can be powered with mini-B cable. It is also used as USART connection for debug logs from host. Serial port communicaton program like tera term or minicom used to print the logs.
  • BT/BLE support will be added in upcoming release.

Hardware connections for ESP32

STM32 Pin ESP32 Pin ESP32-S2/S3 ESP32-C2/C3/C6 Function
PB4 (pin5) IO19 IO13 IO2 MISO
PA5 (pin7) IO18 IO12 IO6 CLK
PB5 (pin9) IO23 IO11 IO7 MOSI
PA15 (pin11) IO5 IO10 IO10 CS
GND (pin2) GND GND GND GND
PC6 (pin6) IO2 IO2 IO3 Handshake
PC7 (pin8) IO4 IO4 IO4 Data Ready from ESP
PB13 (pin10) EN RST RST Reset ESP

SPI setup sample image with ESP32-C6 as slave & STM32 as Host: alt text

  • Use good quality extremely small (smaller than 10cm) jumper wires, all equal length
  • Optionally, Add external pull-up of min 10k Ohm on CS line just to prevent bus floating
  • In case of ESP32-S3, For avoidance of doubt, You can power using UART port

2. ESP peripheral setup

One can load pre-built release binaries on ESP peripheral or compile those from source. Below subsection explains both these methods.

2.1 Load Pre-built Release Binaries

  • Download pre-built firmware binaries from releases
  • Follow readme.txt from release tarball to flash the ESP binary
  • ⚠️ Make sure that you use Source code (zip) in Assets fold with associated release for host building.
  • Windows user can use ESP Flash Programming Tool to flash the pre-built binary.
  • Collect firmware log
    • Use minicom or any similar terminal emulator with baud rate 115200 to fetch esp side logs on UART
$ minicom -D <serial_port>

serial_port is device where ESP chipset is detected. For example, /dev/ttyUSB0

2.2 Source Compilation

Make sure that same code base (same git commit) is checked-out/copied at both, ESP and Host

Set-up ESP-IDF
  • Note on Windows 11: you can follow these instructions, instead of the following, to setup ESP-IDF and build the esp firmware.
  • ⚠️ Following command is dangerous. It will revert all your local changes. Stash if need to keep them.
  • Install the ESP-IDF using script
$ cd esp_hosted_fg/esp/esp_driver
$ cmake .
  • Set-Up the build environment using
$ . ./esp-idf/export.sh
# Optionally, You can add alias for this command in ~/.bashrc for later use
Configure, Build & Flash ESP firmware
  • Set slave chipset environment
$ cd network_adapter
$ rm -rf sdkconfig build
$ idf.py set-target <esp_chipset>

where <esp_chipset> could be one from "esp32", "esp32s2", "esp32s3", "esp32c2", "esp32c3", "esp32c6"

  • Execute following command to configure the project
$ idf.py menuconfig
  • This will open project configuration window. To select SPI transport interface, navigate to Example Configuration -> Transport layer -> SPI interface -> select and exit from menuconfig.

⚠️ Skip below step for ESP32-S2/S3/C2/C3/C6. Run for ESP32 only.

  • If ESP32 slave, Change SPI controller to VSPI. Please navigate to Example Configuration → SPI Configuration and change value of SPI controller to use to 3

To build and flash the app on ESP peripheral, run

$ idf.py -p <serial_port> build flash
  • Collect the firmware log using
$ idf.py -p <serial_port> monitor

3. Checking the Setup

  • Firmware log On successful flashing, you should see following entry in ESP log:
[   77.877892] Features supported are:
[   77.877901]   * WLAN
[   77.877906]   * BT/BLE
[   77.877911]     - HCI over SPI
[   77.877916]     - BT/BLE dual mode
  • Host log If the setup is functioning fine, you should receive INIT event similar to above from ESP chipset