DIO protocol

Introduction

The protocol for the DIO, 3FETs and FETs will be explained on this page. Most functions apply to all three boards, but some don't.

This page describes both the SPI and the I2C version. See SPI versus I2C protocols for the explanation about how the protocols work in general.

write ports

On the DIO and related boards all ports just set a single value. So writing more than one byte to such a port is redundant. The last value is the one used. The DIO boards don't have any ports that are logically a stream of bytes. So writing more than one or two bytes is not encouraged.

The DIO, 3FETS and 7FETS boards define several ports:

port	function
0x10	set all outputs (bit 0 is output 0, etc).
0x20 .. 0x27	set one output (0x20 for output 0, 0x21 for output 1 etc)
0x30	define pins as inputs or outputs. 0 means input, 1 means output.
0x40	set current position. (only DIOand 7FETS)
0x41	set target position. (only DIO and 7FETS)
0x42	set relative position. (only DIO and 7FETS)
0x43	set stepdelay. (in tenths of a microsecond, default 200: 20ms between steps). (only DIO and 7FETS)
0xf0	change address.

All the above ports are read/write. I.e. if you read from that port, you will get the current value.

read ports

The DIO, 3FETS, and 7FETS boards support the following read ports:

port	function
0x01	identification string. (terminated with 0).
0x02	read eeprom (serial number).
0x10	read all inputs
0x20 .. 0x27	read one input (0x20 for input 0, 0x21 for input 1 etc)
0x40	read current position. (only DIO and 7FETS)
0x41	read target position. (only DIO and 7FETS)
0x43	read stepdelay. (in tenths of a microsecond, default 200: 20ms between steps). (only DIO and 7FETS)

examples

For SPI in the examples below, "data sent" means the data on the MOSI line, while "data received" means the data on the MISO line. when MISO reads "xx" you should ignore the data. When MOSI reads "xx" it doesn't matter what you send.

For I2C in the examples below, you should first initiate a "write" transaction with the data in the "data sent column". Don't send the "xx" bytes. Then you initiate a "read" transaction, and you will get the data in the "data received" column (and again not the "xx" bytes).

read identification

read the identification string of the board. (SPI_DIO)

data sent	data received	explanation
0x85	xx	select destination with address 0x84 for READ.
0x01	xx	identify
xx	0x73	's'
xx	0x70	'p'
xx	0x69	'i'
xx	...	etc.

turn on all outputs

data sent	data recieved	explanation
0x88	xx	select destination with address 0x88 for WRITE
0x10	xx	set outputs as in bitpattern (next byte)
0xff	xx	All outputs active.

turn on output 4

data sent	data recieved	explanation
0x88	xx	select destination with address 0x88 for WRITE
0x24	xx	port 0x24: output 4...
0xff	xx	... active.

move stepper to step 0x1234

data sent	data recieved	explanation
0x88	xx	select destination with address 0x88 for WRITE
0x41	xx	port 0x41: set target position
0x34	xx	low byte
0x12	xx	high byte.