Difference between revisions of "DIO protocol"

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== set cursor position ==
+
== turn on all outputs ==
 
move to line 1, character 5:
 
move to line 1, character 5:
 
{| border=1
 
{| border=1
 
! data sent !! data recieved || explanation  
 
! data sent !! data recieved || explanation  
 
|-
 
|-
| 0x82 || xx || select destination with address 0x82 for WRITE
+
| 0x88 || xx || select destination with address 0x82 for WRITE
 
|-
 
|-
| 0x11 || xx || port 0x11 = set cursor position.  
+
| 0x10 || xx || port 0x10 all outputs in bitpattern.  
 
|-
 
|-
| 0x25 || xx  || 0x25 = 001 00101 = line 1 position 5.  
+
| 0xff || xx  || All outputs active.
 +
|}
 +
 
 +
== turn on output 4 ==
 +
move to line 1, character 5:
 +
{| border=1
 +
! data sent !! data recieved || explanation
 +
|-
 +
| 0x88 || xx || select destination with address 0x82 for WRITE
 +
|-
 +
| 0x24 || xx || port 0x24: output 4...
 +
|-
 +
| 0xff || xx  || ... active.
 +
|}
 +
 
 +
== move stepper to step 0x1234 ==
 +
move to line 1, character 5:
 +
{| border=1
 +
! data sent !! data recieved || explanation
 +
|-
 +
| 0x88 || xx || select destination with address 0x82 for WRITE
 +
|-
 +
| 0x41 || xx || port 0x41: set target position
 +
|-
 +
| 0x34 || xx  || low byte
 +
|-
 +
| 0x12 || xx  || high byte.  
 
|}
 
|}

Revision as of 19:07, 7 March 2012

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 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)
0x40 set/read current position.
0x41 set/read target position.
0x42 set/read relative position.
0x43 set/read stepdelay. (in tenths of a microsecond, default 200: 20ms between steps).
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_lcd board supports two read ports:

port function
0x01 identification string. (terminated with 0).
0x02 read eeprom (serial number).

examples

read identification

read the identification string of the board. ('spi_lcd 1.3').

data sent data recieved explanation
0x83 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

move to line 1, character 5:

data sent data recieved explanation
0x88 xx select destination with address 0x82 for WRITE
0x10 xx port 0x10 all outputs in bitpattern.
0xff xx All outputs active.

turn on output 4

move to line 1, character 5:

data sent data recieved explanation
0x88 xx select destination with address 0x82 for WRITE
0x24 xx port 0x24: output 4...
0xff xx ... active.

move stepper to step 0x1234

move to line 1, character 5:

data sent data recieved explanation
0x88 xx select destination with address 0x82 for WRITE
0x41 xx port 0x41: set target position
0x34 xx low byte
0x12 xx high byte.