Evaluation Module User's Guide

G.2 GPIO Capability
www.ti.com GPIO Capability
The USB-MODEVM has seven GPIO lines. Access them by specifying the interface to be 0x08, and then
using the standard format for packets—but addresses are unnecessary. The GPIO lines are mapped into
one byte (see Table G-3 ):
Table G-3. GPIO Pin Assignments
Bit 7 6 5 4 3 2 1 0
x P3.5 P3.4 P3.3 P1.3 P1.2 P1.1 P1.0
Example: write P3.5 to a 1, set all others to 0:
[0] 0x18 --> write, GPIO
[1] 0x00 --> this value is ignored
[2] 0x01 --> length - ALWAYS a 1
[3] 0x00 --> this value is ignored
[4] 0x40 --> 01000000
The user may also read back from the GPIO to see the state of the pins. Let's say we just wrote the
previous example to the port pins.
Example: read the GPIO
[0] 0x08 --> read, GPIO
[1] 0x00 --> this value is ignored
[2] 0x01 --> length - ALWAYS a 1
[3] 0x00 --> this value is ignored
The return packet should be:
[0] 0x28
[1] 0x00
[2] 0x01
[3] 0x00
[4] 0x40
SLAU261 – November 2008 USB-MODEVM Protocol 49
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