LoRa-E5-mini

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Project LoRa E5
Arduino on the LoRa-E5-mini devboard
Status In progress
Contact bertrik
Last Update 2021-10-18

The plan

This page is about the LoRa-E5 module and getting it to work as a LoRaWAN node with Arduino and the BasicMac stack.

  • replace the original "AT" firmware with Arduino based firmware
  • use the BasicMac library for LoRaWAN
  • use platformio as the build system
  • create some basic examples for use as a LoRaWAN node on TheThingsNetwork

Interesting post about this module: https://www.disk91.com/2021/technology/lora/lora-e5-the-seeed-studio-stm32-wl-module/

What currently works:

  • can run an Arduino program, compiling from the Arduino IDE
  • blinking the LED works
  • output over serial works

TODO, yet to figure out:

  • add support for the Seeed LoRa E5 mini in the stm32 package
  • get communication going using the internal "subghz" SPI port
    • do I need to enable the APB3 clock domain?
    • be careful about the SUBGHZ SPI clock in combination with SMPS mode
    • get a simple transfer going that proves that meaningful data is exchanged (e.g. default sync word magic number)
  • get basicmac stack working with the "subghz" SPI port (it appears communication in the Arduino version of BasicMac is done using just "SPI", see https://github.com/LacunaSpace/basicmac/blob/master/target/arduino/hal/hal.cpp#L193)
  • get compilation and upload working with platformio

Hardware

The hardware is the LoRa-E5 mini from seeed studio, contains the STM32WLE5JC:

Overview of pins used on this board (not completely standard): https://wiki.seeedstudio.com/LoRa_E5_mini/#22-gpio-configuration-overview

Pins:

  • PA4/PA5: radio rx/tx?
  • PB6/PB7: serial port
  • PB5: onboard LED
  • PB13: onboard button ("BOOT")
  • PA4: internal SUBGHZ SPI NSS, conflicts with RX/TX switch?
  • PA5: internal SUBGHZ SPI SCK, conflicts with RX/TX switch?
  • PA6: internal SUBGHZ SPI MISO
  • PA7: internal SUBGHZ SPI MOSI

LoRa modem

It appears the LoRa functionality is exposed through an internal SPI bus, called SUBGHZSPI in the datasheet.

Also, there are some pins to control the radio path.

Programming over SWD

Connect an ST-LINKv2 as follows:

  • SWDIO to PA13
  • SWCLK to PA14
  • GND to GND

You may need to upgrade the firmware of your STLINKv2, mine is currently at V2J38S7.

Software

Initial experimental firmware can be found at: https://github.com/bertrik/lora-e5

  • blinky example, the most basic of all sketches which makes a LED blink demonstration of successful download of an Arduino program
  • helloworld example, sends a text over the serial port

Updated STM32 support package: https://github.com/bertrik/Arduino_Core_STM32

These examples still uses the Arduino IDE.

There appears to be support for various kinds of WL55 boards in the stm32duino project: https://github.com/stm32duino/Arduino_Core_STM32/blob/main/boards.txt

Support for a generic WLE5JCI board here in the stm32duino archive: https://github.com/stm32duino/Arduino_Core_STM32/blob/main/variants/STM32WLxx/WL54JCI_WL55JCI_WLE4J(8-B-C)I_WLE5J(8-B-C)I/boards_entry.txt#L62

How to add a new variant (board): https://github.com/stm32duino/wiki/wiki/Add-a-new-variant-(board)

Experimental development environment

This uses my own fork, which will include support for the Seeed LoRa E5 mini.

  • Install Arduino IDE 1.8.16, from https://www.arduino.cc/en/software
  • Configure Arduino STM32 support:
    • Add the following board URL (under File / Preferences / Additional board URLs):
 https://github.com/stm32duino/BoardManagerFiles/raw/main/package_stmicroelectronics_index.json
    • Under menu Tools/Board/Boards manager, search for STM32 and install 'STM32 MCU based boards'
  • Install STM Cube for the upload tools:
    • Download and install package en.stm32cubeprg-lin_v2-8-0_v2.8.0.zip
  • Run STM Cube to remove read protection (and erase the device) from the STM32
    • attach the STLink V2 and connect it to the STM32
    • TODO: document, or see the Seeed page
  • Clone my Arduino_Core_STM32 repo into ~/Arduino/hardware
 cd ~/Arduino/hardware
 mkdir -f stm32
 cd stm32
 git clone https://github.com/bertrik/Arduino_Core_STM32
  • Restart the Arduino IDE and select the correct board:
    • Under menu Tools/Board/STM32 boards .... (sketchbook), choose 'Generic STM32WL series' from 'Generic STM32WL series'
    • Under menu Tools/Board part number, choose 'Seeed Studios LoRa E5 mini'

Now you can:

  • Load the helloworld.ino file into the Arduino IDE:
    • Compile and upload with ctrl-U
    • Open serial port with ctrl-shift-M and see that serial messages are coming in

Node configuration in TheThingsNetwork

The information on the website of Seeed studios is outdated. It refers to the "v2" version of TheThingsNetwork, which is being phased out. It is already impossible to add new nodes on TTNv2, since it was set to read-only.

Nodes should be configured for TheThingsNetwork v3 instead.

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