Simple IO Protocol

Simple IO protocol supporting binary and 16 bit analog in-/outputs (originally named ASEB protocol).

The first byte of a packet (address) and the last (checksum) are left out in all packet descriptions/representations on this page.

Overview

• A maximum of 16 channels are supported for each input and output type, the exact number can be set.
• An index is assigned to each channel.
• All input values are read out at once with the Sync command.
• Outputs are set with separate commands.
• Setting initial values is error-free by definition - the device should ensure that this is fulfilled.
• Outputs can have an initial value other than 0. Therefore it is possible to read the status of outputs.

16-bit values are transmitted as Little Endian.

IO type	Index range	Description
Digital Inputs	1-16	Transmitted as a 16-bit bit mask regardless of the exact number.
Analog Inputs	17-32	Signed 16 bit values.
Digital Outputs	33-48	Transmitted as byte value.
Analog Outputs	49-64	Signed 16 bit values.

Basic commands

Name	Request	Response
Sync	<0xFF>	[<digital inputs if at least one available, 2 byte>][<1. analog input, 2 byte>][<2. analog input>][...]
Set digital output	<Index><Byte>	<empty packet>
Set analog output	<Index><Low-Byte><High-Byte>	<empty packet>
Read digital output value	<Index>	<Byte>
Read analog output value	<Index>	<Low-Byte><High-Byte>

Extended commands

Commands to query information about the available channels. The request always consists of one byte with the command + possibly the index of a channel. The answer is usually a number with a length between 1 and 4 bytes.

Command	Command Key	Channel index required as 2. byte?	Response length
Length of a Sync Response	0xF4	-	uint8
Number of digital inputs	0xF7	-	uint8
Number of digital outputs	0xF8	-	uint8
Number of analog inputs	0xF9	-	uint8
Number of analog outputs	0xFC	-	uint8
Length of channel label	0xF6	yes	uint8
Channel label	0xF5	yes	variable