AXIOMTEK CAPA13S Series, User Manual

Page: 67 / 69

CAPA13S Capa Board
Digital I/O 61
Appendix B
Digital I/O
B.1 About Digital I/O
The onboard GPIO or digital I/O has 8 bits. Each bit can be set to function as input or output by
software programming. In default, all pins are pulled high with +5V level (according to main
power). The BIOS default settings are 4 inputs and 4 outputs.
CN8
B.2 Digital I/O Programming
⚫ I 2 C to GPIO PCA9554PW GPIO.
⚫
I
2
C address: 01000100.
Command byte
Command Protocol Function
0 Read byte Input port register
1 Read/write byte Output port register
2 Read/write byte Polarity inversion register
3 Read/write byte Configuration register
The command byte is the first byte to follow the address byte during a write transmission. It is
used as a pointer to determine which of the following registers will be written or read.
Pin Signal Pin Signal
1 DIO0 2 DIO7
3 DIO1 4 DIO6
5 DIO2 6 DIO5
7 DIO3 8 DIO4
9 +5V 10 GND