LoRa-E5-Tiny

Based on LoRa-E5 from Seedstudio, but I wanted something really Tiny so I removed loy of stuff and left only JTAG prog, Serial and I2C Stemma QWIIC connector, and of course cell coin handler.

👀 take a look on this excellent reading on how to use capacitor to prolong cell coin batteries and understand the risk. I will use for EU8868 so for peaks approx 40mA, 3 times less than in the article so I guess it could works with 2 x 220uF or 470uF capacitors. Challenge would be to find them in 1206 footprint format.

I'm using mainly to flash custom firmware in it, and not using AT default firmware.

⚠️ These boards have been received they works as expected but stil not tried with cell coin powering

Challenges

With this consumption issue discovered on LoRa-E5 boards (but also on RAK3172) I'm not confident it will works on Cell Coin CR2450 battery even if I added 2 330uF capacitors on 3.3V rail.

Features

• LoRa-E5 Module
• FTDI SMD 6 pads edge connector (:warning: use 3.3V FTDI One, not 5V)
• JTAG SMD 6 pads edge connector to flash module (PA13-SWDIO / PA14-SWCLK / PB3-SWO / RESET)
• Green Led on PB13
• Red Led on PA9
• 2 Tactile Switches (boot and reset)
• u-FL Antenna connector
• Stemma QWIIC I2C connector
• 2 x 1206 footprint for big capacitors see reading
• CR2450 Cell coin battery size
• CR2450 battery holder

Detailed Description

No specific documentation for now, it's just a kind of wiring helper as schematic.

I also assume that you are familiar with all LoRaWAN stuff, all setup/infrastructure/network server/provisionning and other are out of scope of this repository.

Schematics

Boards

You can order board on oshpark.

• V1.0

It's a pitty after several discuss with OSHPark that I can't have any rewards for each people ordering my boards, this would allow me to order free PCB for shared projects and create new ones. For information my shared boards generated a total of $285 162.00 orders at PCBs.io in 4 years, not bad at all :-), but looks like they have gone 😭

Hoping one day OSHparks will thanks me giving them this market.

Assembled boards

Top & bottom side V1.0

Bill Of Material

Nothing fancy, due to size constraint, components are 0603/1206 and can be ordered almost anywhere (digikey, mouser, radiospare, ...). use only what you need dependings on what you want to do.

📝 I2C pullup may not needed, most QWIIC/Steamma boards have their own.

Check Seeed format BOM File, check on Seeed OPL for manufacturer SKU match.

Test Board out of factory stock

When the boards are from factory, default AT firmware is flashed and thus we have the possibility to test the board before flashing custom firmware and maily also get defaults keys from device.

To do so, connect a 3V3 FTDI Type USB/Serial to access Serial Console

⚠️ Do not use 5V configured FTDI

I personnaly use these one for Sparkun but you can find clones anywhere on the Web.

Once done open Serial terminal (the one from FTDI Serial Port) configured as 9600 BPS 8N1, no flow control, echo typed characters and set to CR+LF for enter key, press reset button and you should be able to see banner

• Connect FTDI on the 6 pins edge header of the board (if PCB is 2mm thickness should works without soldering)
• use them a terminal application and open the port on your computer corresponding to the FTDI device
• set terminal settings to 9600 bauds 8 bits no parity 1 stop bit (8N1)

Once done open Serial terminal (the one from FTDI Serial Port) configured as 9600 BPS 8N1, no flow control, echo typed characters and set to CR+LF for enter key

Then type AT command to see if the LoRa board answer, in this example the board answered +AT: OK which is correct

AT 
+AT: OK

Now get the device version

AT+VER 
+VER: 4.0.11

Now get the device information

AT+ID  
+ID: DevAddr, 24:90:08:93
+ID: DevEui, 2C:F7:F1:20:24:90:08:93
+ID: AppEui, 80:00:00:00:00:00:00:06

I'm using TTN for testing so please follow excellent RAK guide on how to provision your device onto TTN here

In our case we will use the AppKey generated from TTN when provisionning device, just provision your device onto TTN, get the key and put into the device as follow with command AT+KEY=APPKEY in our case AppKey is B7536DCEFB1EBC4AB9871293F6FA7DB5

AT+KEY=APPKEY,"B7536DCEFB1EBC4AB9871293F6FA7DB5" 
+KEY: APPKEY B7536DCEFB1EBC4AB9871293F6FA7DB5

Set ADR + Frequency Plan EU868 + OTAA

AT+ADR=ON   
+ADR: ON
AT+DR=EU868  
+DR: EU868
AT+MODE=LWOTAA 
+MODE: LWOTAA

Check Frequency Plan

AT+DR=SCHEME 
+DR: EU868
+DR: EU868 DR0  SF12 BW125K 
+DR: EU868 DR1  SF11 BW125K 
+DR: EU868 DR2  SF10 BW125K 
+DR: EU868 DR3  SF9  BW125K 
+DR: EU868 DR4  SF8  BW125K 
+DR: EU868 DR5  SF7  BW125K 
+DR: EU868 DR6  SF7  BW250K 
+DR: EU868 DR7  FSK  50kbps 
+DR: EU868 DR8  RFU
+DR: EU868 DR9  RFU
+DR: EU868 DR10 RFU
+DR: EU868 DR11 RFU
+DR: EU868 DR12 RFU
+DR: EU868 DR13 RFU
+DR: EU868 DR14 RFU
+DR: EU868 DR15 RFU

Now time to join (be sure device is provisioned on TTN and you have a TTN gateway around)

AT+JOIN 
+JOIN: Start
+JOIN: NORMAL
+JOIN: Network joined
+JOIN: NetID 000013 DevAddr 26:0B:63:94
+JOIN: Done

Now send confirmed Hello World message

AT+CMSG="Hello World"  
+CMSG: Start
+CMSG: Wait ACK
+CMSG: FPENDING
+CMSG: ACK Received
+CMSG: RXWIN1, RSSI -40, SNR 5.0
+CMSG: Done

Compile and flash Firmware

You can flash the board with excellent mbed-os framework. Easy way is to use mbed studio IDE. We added this board into stm32customtargets, don't hesitate to read the readme. Finally the main firmware mbed-os-example-lorawan program.

Once IDE installed:

• use file / import program and them import the example with URL https://github.com/ARMmbed/mbed-os-example-lorawan
• right click in the project name and select Add Library and enter https://github.com/ARMmbed/stm32customtargets
• open the file custom_targets.json from folder stm32customtargets and copy whole contents
• paste copied contents in the main root folder file custom_targets.json (yes replace the whole file)
• open the file mbed_app.json and change parameters on the section target_overrides
  • LoRaWAN parameters such as frequency plan, OTAA, Duty Cycle, ...
  • replace keys with the ones you got from above step lora.device-eui, lora.application-eui and lora.application-key
• add the following section near the end of the file mbed_app.json.

        "LORA_E5_TINY": {
            "stm32wl-lora-driver.rf_switch_config": 2,
            "stm32wl-lora-driver.debug_rx": "LED1",
            "stm32wl-lora-driver.debug_tx": "LED2",
            "stm32wl-lora-driver.debug_invert": 1
        }

Then on IDE select target "LORA_E5_TINY", build and flash with your favorite programmer (I'm using STLink) with GND/SWDIO/SWDCLK/RESET connected.

Pay attention, that 1st time you need to erase SeeeStudio original firmware, make sure the Read Out Protection of the device is AA. If it is shown as BB, select AA and click Apply. See the end of this section on how to do that with STM32CubeProgrammer.

Build and Flash

From IDE you can build the example. If you plug your STLink while project opened, mbed ide will ask you if you want to set it up for this project/target, once approved you can compile, flash and even debug from mbed ide (need some tools installed, read, very nice.

You can also see logs with the FTDI adapter and any Serial terminal set to 115200 bauds 8 bits no parity 1 stop bit (8N1)

Mbed LoRaWANStack initialized 
 CONFIRMED message retries : 3 
 Adaptive data  rate (ADR) - Enabled 
 Connection - In Progress ...
 Connection - Successful 
 Dummy Sensor Value = 3 
 23 bytes scheduled for transmission 
 Message Sent to Network Server 
 Dummy Sensor Value = 5 
 23 bytes scheduled for transmission 
 Message Sent to Network Server 
 Dummy Sensor Value = 7 
 23 bytes scheduled for transmission 

Green LED will be on when on receive mode and Red when sending data.

License

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License