Command format:

  <command><SP><arg1><SP>...<argN><CR><LF>

Where:
  command - alphanumeric command name
  argN    - numeric argument (unsigned base 10, 0-65535)

Positive response format:

  0<SP><arg1><SP>...<argN><CR><LF>

Where:
  argN   - numeric value (unsigned base 10, 0-65535)

Negative response format:

  -N<SP>"<desc>"<CR><LF>

Where:
  -N    - numeric error code (negative number)
  desc  - verbose error description

# Write digital outputs (masked)
> dout 120 240
< 0

# Read digital inputs
> din
< 0 125

# Read analog inputs
> ain
< 0 32 121 35 31

# Wait specified amount of milliseconds
> sleep 300
< 0

# Return firmware major version, minor version and revision
> vers
< 0 1 42 0

# Reset board
< reset
> 0

# Ping/nop
< ping
> 0

# NOP (empty command)
>
< (ignored)

# Comments
> # foo bar foobar
< (ignored)

# Unknown command
> sing
< -1 "Unknown command"

# Missing parameter
> dout 
< -2 "Required parameter missing"

# Too many parameters
> din 42 666
< -3 "Too many parameters"

# Malformed command
> dout %'I!
< -4 "Invalid parameter"

# Attention
> <CTRL-C> or <CTRL-D>
< 1 "Uh?"


To recover from a possibly unknown board status,
a client should begin the conversation by issuing
an attention sequence, eventually followed by a reset.