WellyNet

	WellyNet is a design for a simple, asyncronous communications bus for use on
	microcontroller devices that operates in a half duplex multi-master mode.

	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
	NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in
	RFC 2119.

SOFTWARE

	Devices MUST start communications with an 8 bit destination address
	Devices MUST NOT use 0 and 255 addresses
	Devices MUST NOT attempt communications if the transmit activity line is high (do not disturb sign)
	Devices MUST have a random or unique back off (10-100us)
	Devices MUST communicate at 9600 bits per second (bps)
	All devices MUST receive and interpret data addressed to 0x00
	Devices MUST receive and interpret data sent to their addresses
	Devices MAY receive and interpret data addressed to 255
	Messages beginning with ASCII « E » SHALL BE interpreted as an event
	Messages beginning with ASCII « A » SHALL BE interpreted as an instruction
	Messages beginning with ASCII « T » SHALL BE interpreted as a test
	Messages MUST contain a 5 bit payload. Where the payload is not required 0x00 SHALL be transmitted for each bit.
	Messages MUST contain a checksum byte at the end of transmission. The checksum MUST be calculated using a longitudinal redundancy check as described in ISO 1155

ELECTRICAL

	Devices MUST use a 5V TTL (Transistor to Transistor Level)
	Devices MAY draw up to 5mA
	All devices with on-board regulation MUST NOT connect the VCC line to the on-board VCC (if devices requires on-board regulations, can use optical isolation)
	Unused pins on the Header MUST BE put in a High impedance state
	The bus MUST BE supplied with a stable 5V supply of at least 2A

CONNECTOR

	WellyNet devices MUST use the standard 6 pin header as shown in figure 1. This connector is identical electrically and mechanically to the AVR ISP, the port MAY be used for
	both programming and WellyNet communications.

	Figure 1:
 		        +-------+
		TLK  ---|-O   O-|--  VCC
		DND  -| |-O   O-|--  NC
		NC   ---|-O   O-|--  GND
		        +-------+
NOTES
Any digital line on the ATtiny can be used
Header: Dest | Send
NC: non-connected
DND: do not disturb
Rx → TLK (Talk): MISO
Tx → NC: MOSI

TO DO LIST
Reference implementation board
Create our library
Create code list
AVR ISP (6 pin header) diagram -