Difference between revisions of "DIO protocol"

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

Revision as of 16:53, 4 May 2012

Introduction

The protocol for the SPI_dio, SPI_3FETs and SPI_7FETs will be explained on this page. Most functions apply to all three boards, but some don't.

The addresses on the SPI bus are 7 bits wide. The lower bit specifies if the transaction is to be a read or a write. Write transactions have the lower bit cleared (0), read transactions have the lower bit set (1).

Each transaction on the SPI bus starts with the address of the board. The spi_lcd board will ignore any transactions on the SPI bus that do not start with its own address.

After the address a single byte indicates the "port" on the board that the data is written to. The software can thus define 256 ports on each board.

Also see the general SPI protocol


write ports

Some ports just set a single value. So writing more than one byte to such a port is redundant. Other ports are logically a stream of bytes. So writing more than one byte is encouraged.

The spi_dio, spi_3fets and spi_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 spi_dio and spi_7fets)
0x41 set target position. (only spi_dio and spi_7fets)
0x42 set relative position. (only spi_dio and spi_7fets)
0x43 set stepdelay. (in tenths of a microsecond, default 200: 20ms between steps). (only spi_dio and spi_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 spi_dio, spi_3fets and spi_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 spi_dio and spi_7fets)
0x41 read target position. (only spi_dio and spi_7fets)
0x43 read stepdelay. (in tenths of a microsecond, default 200: 20ms between steps). (only spi_dio and spi_7fets)

examples

read identification

read the identification string of the board. (spi_dio)

data sent data recieved explanation
0x85 xx select destination with address 0x82 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.