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H.2
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
Bit 7
6
x
P3.5
Example: write P3.5 to a 1, set all others to 0:
--> write, GPIO
[0] 0x18
--> this value is ignored
[1] 0x00
--> length - ALWAYS a 1
[2] 0x01
--> this value is ignored
[3] 0x00
--> 01000000
[4] 0x40
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
--> read, GPIO
[0] 0x08
--> this value is ignored
[1] 0x00
--> length - ALWAYS a 1
[2] 0x01
--> this value is ignored
[3] 0x00
The return packet should be:
[0] 0x28
[1] 0x00
[2] 0x01
[3] 0x00
[4] 0x40
H.3
Writing Scripts
A script is simply a text file that contains data to send to the serial control buses. The scripting language is
quite simple, as is the parser for the language. Therefore, the program is not forgiving about mistakes
made in the source script file, but the formatting of the file is simple. Consequently, mistakes should be
rare.
SLAU219A – August 2007 – Revised January 2014
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13):
Table 13. GPIO Pin Assignments
5
4
P3.4
P3.3
Copyright © 2007–2014, Texas Instruments Incorporated
3
2
P1.3
P1.2
GPIO Capability
1
0
P1.1
P1.0
53
USB-MODEVM Protocol
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