8: GPIO Interface
DeviceLinx™ XPort Direct/XChip Direct SoC User Guide
45
Control Protocol
The GPIO control protocol is a simple, proprietary protocol.
Guidelines
The GPIO control protocol is described from the PC side.
Send
means from PC to
XPort Direct
.
Response
comes from
XPort Direct
to PC.
The protocol allows for control of up to 32 GPIOs. How many are actually available
depends on the product.
XPort Direct
has only two.
The parameters are four bytes long and represent GPIOs 0-31, with GPIO0 in bit 0 of
the first byte (Little Endian). Parameter bits for configurable pins not configured as
GPIOs are undefined for
Get
commands and ignored on
Set
commands.
Every command consists of nine bytes: one command type of one byte and two
parameters of four bytes each.
Command
Parameter 1
Parameter 2
0 1 2 3 4 5 6 7 8
On some commands, one or all parameters are ignored.
For UDP, command type and parameters need to be in the same datagram.
Responses to valid commands are always five bytes long, consisting of the returned
command byte and as parameters in the current or updated values. In case of an
invalid command, only one byte with value 0FFh is returned.
Command
Parameter 1
0 1 2 3 4
When sending a command (TCP and UDP), wait for the response before sending the
next command.
Commands
Byte 0 Command Types
10h
Get functions
11h
Get directions
(input or output)
12h
Get active levels
(high active or low active)
13h
Get current states
(active or not active)
19h
Set directions
1Ah
Set active levels
1Bh
Set current states
There is no
Set functions
command. Since the pin’s function depends on the
hardware in which the
XPort Direct
is embedded, that configuration is only allowed
using 77FE. Settings changed by any of the
Set
commands are not stored and are
lost when the unit is powered down or rebooted.