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C.3 GPIO Capability
GPIO Capability
The USB-MODEVM has seven GPIO lines. Access the lines 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 C-3 ):
Table C-3. GPIO Pin Assignments
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. If the user 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
SLAU201 – November 2006 USB-MODEVM Communications Protocol 35
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