Mini LoRa Save

Arduino Mini Lora Battery/Sensors Board

Project README

Mini Lora Node, Arduino Mini LoraWAN sensor

At the begining this PCB has been created to help wiring between Arduino Mini and RFM95 Lora module and to be able to put the whole thing powered by various Batteries type (AA, 18650, A, ...).

Then I decided to add some funky stuff like:

new in V1.2

  • Footprint for Ultra Low Power controller TPL5110
  • R9 1206 or PTH Footprint to easily change resistor and thus delay between wake
  • renamed silk pin to function instead of arduino name
  • Optional Tactile Switch to wake from TPL5110

all version

  • Easy to build and solder, 0805 or PTH components
  • I2C connector (or grove) to be able to add internal/external sensors such as BME280, SI7021 or HTU21D
  • Footprint for Lora RFM95
  • Footprint for a Microchip 24AA02E64T EUID
  • RBG Led
  • Optional Tactile Switch
  • Various Battery Connector and type AA/A/18650/CR123
  • Two A4/A5 pins position so you can use different Mini Clone (see BOM)

On version 1.1, I2C A4/A5 (the ones bottom right) are not connected, thanks to tkerby who detected this point on issue #1. This is now fixed on version 1.1a. PCB have been updated.

Detailed Description

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

 Arduino Mini   RFM9x Module
 A0          <----> RST
 MISO  (D12) <----> MISO
 MOSI  (D11) <----> MOSI
 SCK   (D13) <----> CLK
 SS    (D10) <----> SEL (Chip Select)
 D2          <----> DIO0
 D7          <----> DIO1
 D8          <----> DIO2

 Arduino Mini    Shield PCB
 D3          <----> Push Button (Has Pull Down)
 D9          <----> Led Red
 D6          <----> Led Green
 D5          <----> Led Blue
 A1          <----> DONE of TPL5110 (to indicate we done)
 A2          <----> DRVN of TPL5110 (pulse out to wake CPU)
 SDA (A4)    <----> I2C SCL Connector
 SCL (A5)    <----> I2C SDA Connector

R9 determine Wake Time interval from TPL5110 as follow

  • 170K 2 hours
  • 120K ~1 hour
  • 100K ~35 min
  • 47K ~6 min

please read TPL5110 datasheet for more information or Adafruit TPL5110 Learning page


If you're using Battery clip connector, please isolate the A4/A5 and FTDI (V1.0 only) pads from clip because it will do shorts and prevent I2C to work.

I'm Using the LMIC stack as his with custom sketch, this one is under NDA for Ultra Low Power, So I can't provide it but you can use the one in example of LMIC.

You may need to disable debug of LMIC stack if missing.

I'm also changing the Bootloader to use optiboot and win 1.5K of flash code and setup the Brown Out Detect to 1.8V to be able to works under 2.7V. Please see this Pro-Mini-ICSP-FTDI repo if you need to flash your Arduino Pro Mini with this bootloader. You'll see in bootloader folder, I've compiled some for various Speed and for 8MHz and 16MHz Crystal (I use the 250KBPS one, it's fast and reliable).

I've also created custom board definition for Arduino IDE so if using my bootloader, you'll have the board clock and serial speed selection in Arduino IDE, it located here



Top & bottom side V1.2

Top & bottom side Grove V1.1

You can order PCBs of this board at give me some reward when you order my designed boards from their site. This is pretty good, because I can use these rewards to create and design new boards and order boards for a discounted price, so if you don't care about PCB manufacturer please use

Looks like is gone, I do not have any rewards from since August 2020 and my free order placed after are still not received, so my guess they are not on business anymore.

So you can order the board on oshpark.

  • V1.2 Classic I2C connector
  • V1.1a Groove I2C connector

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 in 4 years, not bad at all :-)

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

Assembled boards with sensors

Fully assembled with sensors

Sensors values en Cayenne Monitoring with external sensors

Bill Of Material

Nothing fancy, all components are 0805 and/or PTH and can be ordered almost anywhere (digikey, mouser, radiospare, ...). use only what you need dependings on what you want to do.

Octopart BOM file

Example of option parts, and other source

  • Arduino Pro Mini (just take care your board has A4/A5 at the correct place, some clone are not)
    • Geekcreit 5V 16MHz (power it with 3.3V and/or remove regulator)
    • ebay 3V3 8MHz
  • RFM95 (check Frequency)
  • Common Anode RGB Led, search diffused 5MM RGB LED common anode on ebay
  • Battery Connector format
  • Batteries
    • 3.0V Lithium CR123
    • 3.6V Lithium Thionyle Chloride 2600mAh
    • 3.6V Lithium Thionyle Chloride 3600mAh


Creative Commons Attribution-NonCommercial 4.0

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License
If you want to do commercial stuff with this project, please contact CH2i company so we can organize an simple agreement.


See TTN dedicated post and news and other projects on my blog

Open Source Agenda is not affiliated with "Mini LoRa" Project. README Source: hallard/Mini-LoRa
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