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Wi-Fi and BT/BLE connectivity Setup over SPI

1. Setup

1.1 Hardware Setup

In this setup, ESP board acts as a SPI peripheral and provides Wi-Fi capabilities to host. Please connect ESP peripheral to Raspberry-Pi with jumper cables as mentioned below. It may be good to use small length cables to ensure signal integrity. Power ESP32 and Raspberry Pi separately with a power supply that provide sufficient power. ESP32 can be powered through PC using micro-USB cable.

Raspberry-Pi pinout can be found here!

1.1.1 ESP32 setup

Raspberry-Pi Pin ESP32 Pin Function
24 IO5 CS0
23 IO18 SCLK
21 IO19 MISO
19 IO23 MOSI
25 GND Ground
11 IO2 Handshake
13 IO4 Data Ready
31 EN ESP32 Reset

Setup image is here.

alt text

1.1.2 ESP32-S2 setup

Raspberry-Pi Pin ESP32-S2 Pin Function
24 IO10 CS0
23 IO12 SCLK
21 IO13 MISO
19 IO11 MOSI
25 GND Ground
11 IO2 Handshake
13 IO4 Data ready
31 RST ESP32 Reset

Setup image is here.

alt text

1.2 Raspberry-Pi Software Setup

The SPI master driver is disabled by default on Raspberry-Pi OS. To enable it add following commands in /boot/config.txt file

dtparam=spi=on
dtoverlay=disable-bt

Please reboot Raspberry-Pi after changing this file.

2. Load ESP-Hosted Solution

2.1 Host Software

  • Execute following commands in root directory of cloned ESP-Hosted repository on Raspberry-Pi
$ cd host/linux/host_control/
$ ./rpi_init.sh spi
  • This script compiles and loads host driver on Raspberry-Pi. It also creates virtual serial interface /dev/esps0 which is used as a control interface for Wi-Fi on ESP peripheral

2.2 ESP Peripheral Firmware

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

2.2.1 Load Pre-built Release Binaries

  • Download pre-built firmware binaries from releases
  • Linux users can run below command to flash these binaries.
ESP32
$ python esptool.py --chip esp32 --port <serial_port> --baud 960000 --before default_reset \
--after hard_reset write_flash -z --flash_mode dio --flash_freq 40m --flash_size detect \
0x1000 esp_hosted_bootloader_esp32_spi_v<release_version>.bin \
0x10000 esp_hosted_firmware_esp32_spi_v<release_version>.bin \
0x8000 esp_hosted_partition-table_esp32_spi_v<release_version>.bin

Where,
	<serial_port>    : serial port of ESP peripheral
	<release_version>: 0.1,0.2 etc. Latest from [release page](https://github.com/espressif/esp-hosted/releases)
  • This command will flash SPI interface binaries on esp32 chip.
ESP32-S2
$ python esptool.py --port <serial_port> --baud 960000 --before default_reset --after hard_reset \
--chip esp32s2  write_flash --flash_mode dio --flash_size detect --flash_freq 80m \
0x1000 esp_hosted_bootloader_esp32s2_spi_v<release_version>.bin \
0x8000 esp_hosted_partition-table_esp32s2_spi_v<release_version>.bin \
0x10000 esp_hosted_firmware_esp32s2_spi_v<release_version>.bin

Where,
	<serial_port>    : serial port of ESP peripheral
	<release_version>: 0.1,0.2 etc. Latest from [release page](https://github.com/espressif/esp-hosted/releases)

  • This command will flash SPI interface binaries on esp32s2 chip.

  • Windows user can use ESP Flash Programming Tool to flash the pre-built binary.

2.2.2 Source Compilation

⚠️Note: Please check ESP-IDF Setup and use appropriate ESP-IDF version

  • In root directory of ESP-Hosted repository, execute below command
$ cd esp/esp_driver/network_adapter
Using cmake
  • Set target if the ESP32S2 is being used. Skip if ESP32 is being used.
$ idf.py set-target esp32s2
  • Execute following command to configure 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.
  • Use below command to compile and flash the project. Replace <serial_port> with ESP peripheral's serial port.
$ idf.py -p <serial_port> build flash
Using make

⚠️ make build system is only supported till ESP32. Please refer cmake section above for ESP32-S2.

  • Execute following command to configure project
$ make 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.
  • Use below command to compile and flash the project
$ make
$ make flash

3. Checking the Setup for SPI

Once ESP peripheral has a valid firmware and booted successfully, you should be able to see successful enumeration on Raspberry Pi side as:

$ dmesg
[   47.150740] OF: overlay: WARNING: memory leak will occur if overlay removed, property: /soc/spi@7e204000/spidev@0/status
[   47.346754] Bluetooth: Core ver 2.22
[   47.346812] NET: Registered protocol family 31
[   47.346815] Bluetooth: HCI device and connection manager initialized
[   47.346830] Bluetooth: HCI socket layer initialized
[   47.346837] Bluetooth: L2CAP socket layer initialized
[   47.346856] Bluetooth: SCO socket layer initialized
[   65.589406] esp32_spi: loading out-of-tree module taints kernel.
[   65.591409] esp32: Resetpin of Host is 6
[   65.591541] esp32: Triggering ESP reset.
[   65.593385] ESP32 device is registered to SPI bus [0],chip select [0]
[   66.201597] Received INIT event from esp32
[   66.201613] ESP32 capabilities: 0x78
[   66.619381] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[   66.619388] Bluetooth: BNEP filters: protocol multicast
[   66.619404] Bluetooth: BNEP socket layer initialized