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PJON (Padded Jittering Operative Network) is an Arduino compatible, multi-master, multi-media communications bus system. It proposes a Standard, it is designed as a framework to ease digital communication and it implements a totally software emulated network protocol stack. Its more common applications are in the field of automation, internet of things and industry 4.0. Extended tests proved its effectiveness on different media like electricity, radio and light. See the video introduction to have a brief overview.

Why PJON?

PJON is a tool created to simplify communication between devices and network engineering. Choose the medium you prefer, build your own network of devices and make it work with few lines of code. There are 13 strategies available to communicate data with PJON on various media:

Strategy	Physical layer	Protocol
AS AnalogSampling	Light pulses over air or optic fiber	PJDLS
OS OverSampling	Electrical/radio impulses over wire/air	PJDLR
SB SoftwareBitBang	Electrical impulses over conductive element	PJDL
TS ThroughSerial	Electrical/radio impulses over wire/air	TSDL
TS ThroughSerialAsync	Electrical/radio impulses over wire/air	TSDL
ET EthernetTCP	Electrical/radio impulses over wire/air	TCP
LU LocalUDP	Electrical/radio impulses over wire/air	UDP
GU GlobalUDP	Electrical/radio impulses over wire/air	UDP
DU DualUDP	Electrical/radio impulses over wire/air	UDP
TL ThroughLoRa	Radio impulses over air	LoRa
EN ESPNOW	Radio impulses over air	ESPNOW
LF LocalFile	Shared file system in memory	None
Any	Virtual inheritance, any of the above	Any of the above

Compatibility

Device	AS	OS	SB	TS	ET	LU	GU	DU	TL
Arduino Duemilanove	✔️	✔️	✔️	✔️	✔️	✔️	✔️	✔️	✔️
Arduino Nano	✔️	✔️	✔️	✔️	✔️	✔️	✔️	✔️	✔️
Arduino Uno	✔️	✔️	✔️	✔️	✔️	✔️	✔️	✔️	✔️
Arduino Leonardo	❌	✔️	✔️	✔️	✔️	✔️	✔️	✔️	✔️
Arduino Micro	❌	✔️	✔️	✔️	✔️	✔️	✔️	✔️	✔️
Arduino Mega	✔️	✔️	✔️	✔️	✔️	✔️	✔️	✔️	✔️
Arduino Zero	❌	❌	✔️	✔️	❌	❌	❌	❌	❌
Arduino Due	❌	❌	❌	✔️	❌	❌	❌	❌	❌
ATMega1284P	❌	❌	✔️	✔️	❌	❌	❌	❌	❌
ATtiny84/84A	❌	❌	✔️	✔️	❌	❌	❌	❌	❌
ATtiny85	❌	❌	✔️	✔️	❌	❌	❌	❌	❌
ESP8266	❌	❌	✔️	✔️	❌	❌	✔️	✔️	❌
ESP32	❌	❌	✔️	✔️	❌	✔️	✔️	✔️	❌
STM32F103	❌	❌	✔️	✔️	❌	❌	❌	❌	✔️
Nucleo L053R8	❌	❌	❌	✔️	❌	❌	❌	❌	❌
Nucleo F401RE	❌	❌	❌	✔️	❌	❌	❌	❌	❌
Teensy 3.1	❌	❌	✔️	✔️	❌	❌	❌	❌	❌
Raspberry Pi	❌	❌	❌	✔️	✔️	✔️	✔️	✔️	❌
Windows X86	❌	❌	❌	✔️	✔️	✔️	✔️	✔️	❌
Linux	❌	❌	❌	✔️	✔️	✔️	✔️	✔️	❌
Mac	❌	❌	❌	✔️	❌	✔️	✔️	❌	❌

✔️ compatible - ❌ not compatible

Practical test

After selecting the medium to be used you can start to build your personal bus (that can be made by only two devices for testing):

 Arduino UNO        Arduino UNO
  _________   wire   _________
 | ||   |_||___     |         |
 ||       ||   |    ||       ||
 ||       ||   |    ||       ||
 ||       ||   |____||       ||
 |_________|        |_|_|__||_|
                      

A simple entry level test can be to setup a couple of Arduino Duemilanove / Uno boards connected together with one single wire on both pins 12 as described in the illustration above (also sharing commong ground). When the devices are wired it is possible to test their connectivity sending a packet from device 1 to device 2 and see if device 2 receives it blinking a LED:

#include <PJON.h>
PJON<SoftwareBitBang> bus(1); // <Strategy name> bus(selected device id)

void setup() {
  bus.strategy.set_pin(12);
  bus.begin();
  bus.send_repeatedly(2, "B", 1, 1000000); // Send B to device 2 every second
}

void loop() {
  bus.update();
};

As you can see the code above, device 1 is simply sending a "B" every second to the device id 2.

#include <PJON.h>
PJON<SoftwareBitBang> bus(2); // <Strategy name> bus(selected device id)

void setup() {
  pinModeFast(13, OUTPUT);
  digitalWriteFast(13, LOW); // Initialize LED 13 to be off
  bus.strategy.set_pin(12);
  bus.begin();
  bus.set_receiver(receiver_function);
};

void receiver_function(
  uint8_t *payload, 
  uint16_t length, 
  const PJON_Packet_Info &packet_info
) {
  if(payload[0] == 'B') {
    digitalWrite(13, HIGH);
    delay(30);
    digitalWrite(13, LOW);
  }
}

void loop() {
  bus.receive(1000);
};

On the receiver side is declared a receiver function that is called when a packet for the device is received. In this case, the function checks if the received character is "B" and if so, blinks the LED connected to pin 13. You should see the receiver device blinking every second.