ARMAWATCH & ARMACHAT - long range radio messengers

Freedom of communication without borders, operators, networks, fees !
Your own network, your own rules !
Long range radio communicators

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bobricius has 993 orders / 69 reviews
Ships from Slovakia
It is very extremely simple and low component count / cost device.
I called is as armageddon communicator but I think it can not survive any disaster,
I take in focus use only one easy solder MCU and I chose SAMD21E18 in
TQFP32 package (same size as popular Atmega328)

But with many new features as:
-crystal free USB
-Mass storage USB bootloader
-256Kb flash, 32kb RAM
-2xSPI, 1xUART, 1xI2C
-Low power

I making it for fun and learning communication, It is super hi tech walkie talkie,
No special manufacturing tools required, all is made with PCB technology,
Front panel also cary Backlight LEDs for keyboard = it is no waste of PCB electricity functions

Everyday question > "distance"
no direct view, some small hills, some houses in village.

(Max power, Spread Factor 12)
-700m unit on garden desk
-1500m unit in window, about 4m above ground
-4300m unit in attic window, 10m above ground


  • Armachat is Winner of PCBWay 3rd PCB Design Contest 2nd place BEST DESIGN ! 
  • Hackaday Prize Community Vote (Bootstrap Award)


Articles about project:

Searching sponsors, patrons

Experience freedom of communication without borders
fees !!!
Create your own network, your own rules !!!

Summer update, Armawatch, new smaller Armachat and keyboard backlight:

Official Hackaday prize OPERATION VIDEO preview:



Hardware features UPDATED !!!:

  • Only single chip SAMD21E18, more easy to solder in TQFP32
  • QWERTY keyboard - 30 keys (5x6 matrix)
  • 18650 li-on battery
  • LCD on HW SPI:
    - FUSION: 1.8 TFT LCD display 128x160 ST7735 or 240x240 IPS ST7789
  • RFM95 long range radio module - 3 freq. by your country - IRQ / wake up
  • Beeper
  • Battery charging
  • DS3131 RTC with CR1220 battery backup, optional not used now
  • GPS support, optional not used now
  • Environmental sensors possibility, optional not used now
  • native HW USB for next features like, modem, sniffer ....
  • EXPANSION port I2C, UART (GPS, RTC, Environmental sensors)

Working software features:

  • Send message ... compose and send message to specified recipient or broadcast 
  • Receive message ... message is received on background and stored in memory.
  • Message editor ... write message about +/- 80 characters long ...
    80 is now best readable on full display ....
  • Message memory ... all send/received messages are stored in memory
  • Display memory ... display memory content
  • Config ... user radio configuration spread factor / power
  • check message delivery confirmation
  • contact list display with auto updated names from remote units
  • BEST working feature - resend undelivered messages if delivery fail, message is stored with "undelivered" attribute. Every station at power on broadcast "Ready receive status", then if any near station receive this broadcast and have undelivered message automatically try send this messages,  if then receive confirmation mark messages in memory as DELIVERED :)
    All this features uses only 20% flash memory !!!
    there is lot free space for next updates

 TODO software features:

  • add message encryption
  • Message forward between devices to extend range  (mesh
    (Addressing, protocol and packet structure is already implemented)
  • add some USB link features like work as usb modem, send receive/message from PC terminal
  • GPS position parse

Some screenshots:

STEM Learning:

What you can learn on this board?

  • modern architecture based on M0 arduino zero compatible, with lot memory and native USB
  • QWERTY keyboard matrix reading
  • complex input/output HID processing read keyboard data,
  • create and display graphics, save data to flash, send results over radio or usb
  • radio communication with world best, most advanced long range radio technology
  • work with I2C sensors or process GPS data
  • learn lot about network architecture, packets, communication, addresing, delivery confirmation
  • RTC clock and alarms
  • power management, sleep, wake by alarm, wake on receive

( all this things I learning now on this project)

Production and marketing plans:

Hardware is very simple and easy to solder by hand (in pocket version with SAMD21E18), low active component count make it very attractive as learn to solder kit. Unfortunately SAMD21 come without bootloader, this is little problem because SAMD need special tools to burn bootloaders, I have no experience how much is complicated burn bootloader in factory on bare unsoldered chip. I suggesting sell this as semi populated board > PCBA all active components except buttons and radio module (Unsoldered radio module give small...

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Front panel for laser cutter, square buttons. IPS mini display

AutoCAD DXF - 1.02 MB - 10/04/2020 at 21:05


Front panel board gerbes

x-zip-compressed - 127.18 kB - 10/04/2020 at 21:04



Armachat schematic

Portable Network Graphics (PNG) - 68.45 kB - 10/04/2020 at 21:03



Firmware - new interface, protocol preview

uf2 - 512.00 kB - 10/04/2020 at 20:59



Firmware - working, communication software

uf2 - 512.00 kB - 10/04/2020 at 20:59


View all 6 files

  • 1 × RFM95 Radio module with Long range LoRa radio modulation
  • 1 × SAMD21E18 Arduino ZERO compatible MCU in supercool TQFP32 package
  • 1 × DS3231 - optional, not used now Clock and Timer ICs / Real-Time Clocks - Optional
  • 1 × AP2114H-3.3TRG1 regulator 3.3V Power Management ICs / Linear Voltage Regulators and LDOs
  • 1 × MCP73831 Power Management ICs / Power Supply Support

View all 18 components

  • Armachat - Cyberdeck style preview

    bobricius10/04/2020 at 20:51 0 comments

  • New user interface, new meshtastic compatible protocol

    bobricius09/20/2020 at 11:13 0 comments

    Cleaning code ... unifying user interface, rewriting communication, power saving

    Something what is finished now

    • Switching to white background, maybe it is bad step, but why wasting light
      you can change black/white theme in setup
    • New font something middle between old small/big combination
    • User name is auto updated in contact lists on all remote units. 
    • Addressing and protocol adapted for future #meshtastic support.
    • Soon you can send message to #meshtastic network, they nodes forward this message  to another Armachat unit, but you can not read this message on Meshtastic app :(
    • Also working on adaptation Meshtastic mesh routing protocol for armachat (Full interconnection is little hard, but maybe in far future I want this)

    Power management

    I am searching way how to reduce consumption but I found only one way ... reduce backlit

    • MCU 20mA
    • LoRa 10mA
    • Backlit 30mA

    Total 60mA, if I switch-off lora, there is no receiving wake up.
    If MCU go to sleep, display freeze.
    Lowering backlight (no switch-off just to 10%)
    I can go to 30mA with full runtime a little readable display

    Next you can compare user interface (Black unit - OLD. Green unit - NEW UI)





  • Next distance test ... little above 4km

    bobricius09/13/2020 at 19:28 0 comments

    Today I make small bike trip to next village.
    New distance test ... above 4km.

    • 865,2Mhz 
    • LoRa SpreadFactor 12 
    • 3 dbi antenna 
    •  one unit in attic window, second in hand.
    •  No direct view, some small hills and houses

    Not reliable, I need some walking and search.

    Poll for protocol finished, Meshtastic is winner ;) Yesterday I started protocol adaptation. I am not sure if I can fully implement routing in to Armachat device but I want negotiate with Meshtastic authors about injecting packet to Meshtastic network and then forward with they nodes.

    For now I am very satisfied.  I think connection to  2km is very reliable.

    I can imagine solution with only one simple repeating node above hill or church and cover large area with lot of users.

  • Mesh protocol Meshtastic or ???

    bobricius09/11/2020 at 06:11 0 comments

    I created poll about future mesh protocol implemntation.


  • Gold/Green boards with keyboard backlight

    bobricius09/07/2020 at 22:27 0 comments

    #Armachat last version with perfect 30LED keyboard backlight (10mA 0.03W). 

    PCB made in @aislerhq 
    I think I am on edge of perfection.

    Is GOLD/GREEN cool ?

  • Armachat - Distance test

    bobricius07/30/2020 at 20:11 0 comments

    Finally I get time to make small distance test, no direct view, between houses in village.
    700-1500m ... maybe more, standard RFM95 20dB output, spread factor 12, 2dB antenna

    • Unit on garden desk
    • Unit in window, about 4m above ground

  • Cyberdeck style concept.

    bobricius07/03/2020 at 10:47 2 comments

    It is waterproof box for memory cards.
    I need design separated keyboard and main board.
    Of course it is still not doomsday resistant. just for fun ;)

  • RFM95PW - High Power radio module and IPS display

    bobricius06/29/2020 at 21:10 0 comments

    Descriptions of RF LoRa Transceiver Module RFM95PW:

    RFM98PW/RFM95PW RF LoRa Transceiver module series’ design is based on the high performance LoRaTM modulation technique RF98/RF96 chip, It operate at 169/433/470MHz (RFM98PW)  and 868/915MHz(RFM95PW) ISM band , The low receive sensitivity(–136dBm) coupled with Enhanced +30dBm output power ensures extended range and improved link performance.

    240x240 IPS display and square buttons :)

    You can also use bigger TFT display.

    RFM95PW under module is footprint for clasic RFM95, also on board is optionall DS3231 with backup battery.

  • Received new boards

    bobricius06/03/2020 at 22:33 0 comments


    • Routing new board with higher power module RFM95 design is almost ready for factory.
    • Board is little smaller as previous version (-10mm) 62mm x 77mm
    • Accepting both RFM95 and RFM95PW lora modules
    • Maybe is wearable with realy comfort keyboard and bigger display ( Armawatch killer ??? ).

  • Armawatch assembled

    bobricius06/01/2020 at 21:23 0 comments

View all 11 project logs

  • 1
    • there is nothing special, I build 20 prototypes, with hand soldering, without issues

    I am not saying best, they are just my steps :

    • Solder CPU, and all active/passive components
  • 2
    Setup Arduino IDE and bootloader
    • I am using Atmel-ICE, I have no idea about another way how to program bootloader now!

    Arduino > Preferences : Additional boards manager URLs

    Arduino > Tools > Boards manager : MattairTech MT-D21E (rev B)
    Arduino > Tools > Clock > Source : INTERNAL_OSCILLATOR
    Arduino >Tools > Serial config : ONE_UART_ONE_WIRE_TWO_SPI

    Connect GND, VCC, SWC, SWD, Reset to ATMEL-ICE

    Arduino > Tools > Programmer : ATMEL-ICE
    Arduino > Tools > BURN BOOTLOADER

    • Now you can upload sketches with USB

    Or second option:

    From Atmel Studio write special ARMABOT.bin then you can easy upload firmwares drag&drop

  • 3
    Upload first firmware
    • Connect Armachat to computer via USB
    • double press RESET button for bootloader activation
    • display start flashing (breathing)
    • copy first.uf2 to freshly displayed mass storage drive
    • wait for writing
    • press RESET again

    If you hear BEEP firmware is running

View all 6 instructions

Enjoy this project?



RomanS wrote 06/08/2020 at 19:53 point

is it possible to see the firmware source code?

  Are you sure? yes | no

bobricius wrote 06/08/2020 at 20:18 point

on github

  Are you sure? yes | no

RomanS wrote 06/07/2020 at 15:47 point

  Are you sure? yes | no

bobricius wrote 06/08/2020 at 06:06 point

;) I like more

  Are you sure? yes | no

RomanS wrote 06/08/2020 at 07:36 point

yeah. it's a good project. I'm trying to provide LORA communication with my messenger through satellite, like the guy with swiss accent at youtube ) check

"#305 Transfer a LoRa message through space to my PC before 2020" video

  Are you sure? yes | no

Joshua Johnson wrote 06/05/2020 at 17:13 point

How long does the battery last?

  Are you sure? yes | no

bobricius wrote 06/08/2020 at 06:05 point

untested, I measured consumption now it is about 50mA, full display backlit, radio onreceive, CPU at full power, no power saving. 26mA at low backlit. You can easy calculate work time to battery capacity. I start with power saving after I finish radio communication.

  Are you sure? yes | no

sunny wrote 06/04/2020 at 00:02 point  this project can give you some more ideas that you can implement in terms of a gyro keyboard and mouse making it even smaller if you'd like.

Good Luck with it.

  Are you sure? yes | no

paul kaloudis wrote 06/03/2020 at 15:52 point

Any chance of selling this as a kit? I've got a hard time finding the individual parts. Also, I love the idea of a longer range version.

  Are you sure? yes | no

bobricius wrote 06/03/2020 at 22:29 point

Kits is my nightmare, I always forgot some part to include.

  Are you sure? yes | no

paul kaloudis wrote 06/03/2020 at 22:49 point

how about just links to the parts then?

  Are you sure? yes | no

bobricius wrote 06/04/2020 at 08:42 point

I am ordering from TME.EU. prepare component list next week.

  Are you sure? yes | no

Dave's Dev Lab wrote 05/28/2020 at 03:30 point

man you so need to add a barcode scanner to this and beef up the case! you could sell this by the boat load!

  Are you sure? yes | no

bobricius wrote 05/28/2020 at 07:21 point

Thinking about but for Fusion model, there is more space, also redrawing board for 10Km range modules RFM95PW :) ... just  4 days to receive watch boards ;)

  Are you sure? yes | no

Daniel Dunn wrote 07/04/2020 at 07:13 point

Instead of a barcode scanner, why not an expansion port?

  Are you sure? yes | no

bobricius wrote 07/04/2020 at 13:30 point

there is already expansion port, I2C and uart

  Are you sure? yes | no

Hpag wrote 05/20/2020 at 18:05 point

I liked the watch model so much! I wonder what is it capable of besides sending and recieving text messages. I would also like to contribute on this project.

  Are you sure? yes | no

bobricius wrote 05/20/2020 at 18:13 point

Watch and Fusion model have identical circuit and software, difference is only on display dimension. Keyboard I have tested on previous Armachat POCKET and is usable.

  Are you sure? yes | no

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