Hardware Reference
In-Depth Information
Program
mcp23017.c
is shown here:
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mcp23017.c : Interface with MCP23017 I/O Extender Chip
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This code assumes the following :
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1. MCP23017 is configured for address 0x20
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2. RPi's GPIO 17 (GEN0) will be used for sensing interrupts
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3. Assumed there is a pull up on GPIO 17.
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4. MCP23017 GPA4-7 and GPB4-7 will be inputs, with pull-ups.
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5. MCP23017 GPA0-3 and GPB0-3 will be ouputs.
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6. MCP23017 signals interrupt active low.
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7. MCP23017 operating in non-banked register mode.
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Inputs sensed will be copied to outputs :
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1. GPA4-7 copied to GPA0-3
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2. GPB4-7 copied to GPB0-3
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20 #include <stdio.h>
21 #include <stdlib.h>
22 #include <fcntl.h>
23 #include <unistd.h>
24 #include <string.h>
25 #include <errno.h>
26 #include <signal.h>
27 #include <assert.h>
28 #include <sys/ioctl.h>
29 #include <sys/poll.h>
30 #include <linux/i2c.h>
31 #include <linux/i2c-dev.h>
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33 #include "i2c_funcs.c" /
I2C routines
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Change to i2c 0 if using early Raspberry Pi
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36 static const char
node = "/dev/i2c-1";
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38 #define GPIOA 0
39 #define GPIOB 1
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41 #define IODIR 0
42 #define IPOL 1
43 #define GPINTEN 2
44 #define DEFVAL 3
45 #define INTCON 4
46 #define IOCON 5
