|Project LoRa E5|
|Arduino on the LoRa-E5-mini devboard|
This page is about the Seeed Studios LoRa-E5 mini development board 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
- Use this chip/module for transmitting high-altitude balloon telemetry, possibly using 4FSK modulation (not using LoRa)
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
- Reading the button works
- Basic communication with the built-in SX1262 LoRa transceiver
TODO, yet to figure out:
- 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). The problem is that the basicmac LoRaWAN stack expects to talk to a SPI port, while the STM32WL HAL provides higher-level functions to write commands and data, see https://github.com/bertrik/Arduino_Core_STM32/blob/seeed_lora_e5_mini/system/Drivers/STM32WLxx_HAL_Driver/Inc/stm32wlxx_hal_subghz.h#L355 . Internally the STM32 SUBGHZ HAL uses functions like SUBGHZSPI_Transmit that would be a much better fit to the interface expected by the BasicMac stack.
- Get compilation and upload working with platformio
The hardware is the LoRa-E5 mini from seeed studio, contains the STM32WLE5JC:
- LoRa E5 Seeed studio module (just the chip): https://www.seeedstudio.com/LoRa-E5-Wireless-Module-p-4745.html
- LoRa E5 Seeed studio LoRa-E5 mini dev board: https://www.seeedstudio.com/LoRa-E5-mini-STM32WLE5JC-p-4869.html
- LoRa E5 Seeed studio wiki page: https://wiki.seeedstudio.com/LoRa-E5_STM32WLE5JC_Module/
- FCC information about the module: https://fccid.io/Z4T-LORA-E5/
Overview of pins used on this board (not completely standard): https://wiki.seeedstudio.com/LoRa_E5_mini/#22-gpio-configuration-overview
- PA4/PA5: radio rx/tx switch (internal, not available on the footprint of the E5 module)
- PB6/PB7: serial port
- PB5: onboard LED
- PB13: onboard button ("BOOT")
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.
The software consists of an STM32 Arduino development environment with support for the Seeed LoRa E5 mini plus a demonstration sketch.
This uses my own fork of the STM32 packages, which will include support for the Seeed LoRa E5 mini: https://github.com/bertrik/Arduino_Core_STM32/tree/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):
- 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 git checkout seeed_lora_e5_mini
- 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'
A demonstration sketch is 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
Try the helloworld example:
- Connect the LoRa E5 over serial and with an ST-Link v2 as described in https://revspace.nl/LoRa-E5-mini#Programming_over_SWD
- Load the helloworld.ino file into the Arduino IDE:
- Compile and upload with ctrl-U
- See the LED flash
- Open serial port with ctrl-shift-M and see that serial messages are coming in
- Press the BOOT button and see the result on the serial console: it shows the result of reading the syncword registers, proving that we can communicate with the SX1262 LoRa transceiver
Use in high-altitude ballooning
People send up helium balloons and attach a location tracker. A radio transmitter sends telemetry with position, temperature, voltage etc down. The frequencies are often in 70cm band (around 430 MHz), but people are also using LoRaWAN (868 MHz in EU). Modulations used are RTTY (now not so often anymore), 4FSK (a more advanced narrow-band modulation with error correction) and LoRa (either as 'raw' LoRa or LoRaWAN).
Investigate if this module can be used in the 4FSK Mode:
- see https://github.com/projecthorus/horusbinary_radiolib . This in turn uses the RadioLib and uses the SX1262 in basic frequency synthesis mode
- horusbinary -> fsk4_tone -> fsk4_transmitDirect -> phy.transmitDirect
- radiolib/sx1262: transmitDirect -> setRfFrequency -> SPIwriteCommand -> SPITransfer
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.