Arduino Lora based RC system

Features

8 proportional channels and 2 digital channels
Reverse, subrim, Endpoints, Failsafe
Dual rates and expo for Ail, Ele, Rud
Throttle curve and a custom curve with 5 points
Flexible mixer sytem
Adaptable timer and a stopwatch
Model memory
Sticks calibration
Alarms, warnings
Receiver binding
Frequency hopping
External voltage telemetry

License

MIT license

Hardware

Transmitter

2x Atmega328p microcontrollers
1x Semtech SX1276/77/78/79 based rf module
128x64 KS0108 based LCD, or any 128x64 lcd (provide own driver code).
2x Joysticks, 3x two position switches, 1x three position switch, 1x potentiometer
3x push buttons
Additional support components

Receiver

1x Atmega328p mcu
1x Semtech SX1276/77/78/79 based rf module
Additional support components

The schematics can be found in the 'etc' folder under root directory

Compiling

The code compiles on Arduino IDE 1.8.x or higher with board set to Arduino Uno.
The transmitter code is in mtx (master mcu) and stx (slave mcu) folders. The receiver mcu code is in the rx folder. No external libraries are required to compile.
I am using the 433MHz band with the SX1278 modules. If using other modules or frequency band, it is neccessary to edit the frequency lists in the stx.ino and rx.ino files.

User Interface

Three buttons are used for navigation; Up, Select, Down. Long press Select to go Back.
Holding the Down key on home screen accesses the extra digital channels A and B.
Holding the Select key on home screen accesses the trims.
Holding the Select key when swithing on opens the startup menu (for stick recalibration, format eeprom, etc.)

Binding

To bind the receiver and transmitter, use the bind option in the system setup screen. Select bind option and restart the receiver. The LED in receiver blinks on successful bind.

Mixing

This controller implements a free mixer that offers flexiblity with what we want to control. Each mixer slot takes two inputs, multiplexes them, and sends the result to the specified output. Available multiplex options are Add, Multiply, Replace. We can also assign a switch to turn the mix on or off. Mixer slots are evaluated sequentially.

Mixer sources can be any of the following

Raw stick inputs (roll, pitch, thrt, yaw, knob)
Constants (max)
Switches (SwA, SwB, SwC, SwD)
Slowed input (appears with an asterisk)
Curves (Ail, Ele, Thrt, Rud, Cv1)
Channels (Ch1 to Ch8)
Temporary variables (Virt1, Virt2)

The default mapping is Ail->Ch1, Ele->Ch2, Thrt->Ch3, Rud->Ch4, unless overridden in the mixer.

Example mixes

Testing

I have done several tests on this system and found it reliable enough.
The range I got with the SX1278 modules (433MHz at BW 250kHz, SF7, CR 4/5, 17dBm tx power, monopole antennas) was more than 2km line of sight in a semi urban area.
I have also tested the frequency hopping feature and it is stable enough.
The transmitter to receiver update rate is about 40 frames a second which is sufficient to control an RC model. There are no issues experienced with the servo control either.

draman07 / Arduino-LoRa-RC-transmitter-and-reciever