Hardware Reference
In-Depth Information
Source Code
The next few pages list the source code for the program. This was assembled into one
compile unit by using the
#include
directive. This was done to save pages by eliminating
additional header files and
extern
declarations.
■
the source code for
gpio_io.c
is found in Chapter 10 of
Raspberry Pi Hardware
Reference
(apress, 2014).
Note
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2
dht11.c: Direct GPIO access reading DHT11 humidity and temp sensor.
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3
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4
5 #include <stdio.h>
6 #include <stdlib.h>
7 #include <fcntl.h>
8 #include <unistd.h>
9 #include <errno.h>
10 #include <setjmp.h>
11 #include <sys/mman.h>
12 #include <signal.h>
13
14 #include "gpio_io.c" /
GPIO routines
/
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15 #include "timed_wait.c" /
timed_wait()
/
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16
17 static const int gpio_dht11 = 22; /
GPIO pin
/
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18 static jmp_buf timeout_exit; /
longjmp on timeout
/
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19 static int is_signaled = 0; /
Exit program if signaled
/
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20
21/
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22
Signal handler to quit the program:
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23
/
24 static void
25 sigint_handler(int signo) {
26 is_signaled = 1; /
∗
Signal to exit program
/
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27 }
28
29 /
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30
Read the GPIO line status:
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31
/
32 static inline unsigned
33 gread(void) {
34 return gpio_read(gpio_dht11);
35 }
36
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