danielboe/node-serialbuster

Lib for communication over serial, with support for addressing and crc8 check. Suitable for an RS485 bus.

#Node SerialBuster

A protocol for communicating between several nodes on a single serial bus. This protocol is mainly developed for an RS485 network with one master and a number of slave devices.

The library uses https://github.com/voodootikigod/node-serialport for underlying communication.

##Protocol structure

Chunk	Item	Type	Length	Example	Note
0	Start	uint8	1	0x02	Signals start of package
1	Recipient	uint8	1	0x01	Recipient address `0xFF` for broadcast
2	Sender	uint8	1	0x02	Sender address `0x00` for master
3	Length	uint16	2		Length of payload (excluding headers)
4	Payload	uint8[]	N	Hello world!	Any (binary safe) data
5	CRC8	uint8	1		Checksum of header and payload
6	End	uint8	1	0x03	Signals end of package

Broadcast

To send a message to all listening clients use the BROADCAST address 0xFF.

Master

The master device has address MASTER or 0x00.

Error checking

A very lightweight 8bit checksum is calculated for the header + payload data in the envelope. Packages that aren't valid gets dropped. CRC8 is calculated before the packet contents have be escaped. Everything but the start and end bytes are escaped.

Send packet

var serialbuster = require('serialbuster');

var my_node_address = serialbuster.CONSTANTS.MASTER;

var serial = new serialbuster.SerialBuster('/dev/tty.usbserial-A800f7Vn', {
    'baudrate' : 9600
  , 'parser' : serialbuster.parser(my_node_address)
  , 'buffersize' : 1024
});

// Give the serial connection some time to 
// get established after it's first created
setTimeout(function() {
  var packet = new serialbuster.Packet({
      'recipient' : serialbuster.CONSTANTS.BROADCAST // send to all nodes
    , 'sender' : my_node_address
  });
  packet.setPayload("Hello everyone! \n\nlove, master");
  serial.sendPacket(packet);
}, 2000);

Install

npm install git+https://github.com/breakfastny/node-serialbuster

Test

make test

Version History

0.0.6

Perform DNS lookup before connecting to TCP socket. Also preventing clients from writing data to a closed TCP socket.