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<td><img src="images/driver.jpg" width="250"></td>
<td><img src="images/imu-3.jpg" width="250"></td>
<td><img src="images/ir-motion.jpg" width="250"></td>
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<td><center><h2>IR Remote Example</h2></center>
<p>The following code shows one way to read an infrared remote
control device (the sort used in TVs and stereo systems).</p>
<h3>SETUP</h3>
<img alt="fritzing diagram" style="width: 200px; height: 317px;"
src="images/ir-fritz.png" align="left" hspace="10">The device used
is a <span itemprop="name">SFH5110 (IR Receiver for remote control,
carrier 38 kHz).<br>
<br></span> Pin 1 (left from front) may be connected to any spare
gpio. Here it's connected via a 4K7 current limiting
resistor. This isn't really needed as the device has an
internal 23K resistor in-line. It does no harm though.<br>
<br>
Pin 2 should be connected to a Pi ground pin.<br>
<br>
Pin 3 should be connected to a Pi 5V pin.<br>
<p>Here pin 1 to gpio7 (P1-26) via a 4K7 resistor, pin 2 to ground
(P1-14), and pin 3 to 5V (P1-2).<br clear="all"></p>
<p><img src="images/ir-photo.jpg" style=
"width: 500px; height: 500px;" alt="photo of set-up"></p>
<h3>CODE</h3>
<code>#include <stdio.h><br>
<br>
#include <pigpio.h><br>
<br>
#define IR_PIN 7<br>
<br>
#define OUTSIDE_CODE 0<br>
#define INSIDE_CODE 1<br>
<br>
#define MIN_MESSAGE_GAP 3000<br>
#define MAX_MESSAGE_END 3000<br>
<br>
#define MAX_TRANSITIONS 500<br>
<br>
/*<br>
using the FNV-1a
hash <br>
from
http://isthe.com/chongo/tech/comp/fnv/#FNV-param<br>
*/<br>
<br>
#define FNV_PRIME_32 16777619<br>
#define FNV_BASIS_32 2166136261U<br>
<br>
static volatile uint32_t ir_hash = 0;<br>
<br>
typedef struct<br>
{<br>
int state;<br>
int count;<br>
int level;<br>
uint16_t micros[MAX_TRANSITIONS];<br>
} decode_t;<br>
<br>
/* forward declarations */<br>
<br>
void alert(int gpio, int level, uint32_t
tick);<br>
uint32_t getHash(decode_t * decode);<br>
void updateState(decode_t * decode, int
level, uint32_t micros);<br>
<br>
int main(int argc, char * argv[])<br>
{<br>
if (gpioInitialise()<0)<br>
{<br>
return 1 ;<br>
}<br>
<br>
/* IR pin as input */<br>
<br>
gpioSetMode(IR_PIN, PI_INPUT);<br>
<br>
/* 5ms max gap after last pulse */<br>
<br>
gpioSetWatchdog(IR_PIN, 5);<br>
<br>
/* monitor IR level changes */<br>
<br>
gpioSetAlertFunc(IR_PIN, alert);<br>
<br>
while (1)<br>
{<br>
if (ir_hash)<br>
{<br>
/* non-zero means
new decode */<br>
printf("ir code is
%u\ ", ir_hash);<br>
ir_hash = 0;<br>
}<br>
<br>
gpioDelay(100000); /* check remote
10 times per second */<br>
}<br>
<br>
gpioTerminate();<br>
}<br>
<br>
void alert(int gpio, int level, uint32_t tick)<br>
{<br>
static int inited = 0;<br>
<br>
static decode_t activeHigh, activeLow;<br>
<br>
static uint32_t lastTick;<br>
<br>
uint32_t diffTick;<br>
<br>
if (!inited)<br>
{<br>
inited = 1;<br>
<br>
activeHigh.state = OUTSIDE_CODE;
activeHigh.level = PI_LOW;<br>
activeLow.state =
OUTSIDE_CODE; activeLow.level = PI_HIGH;<br>
<br>
lastTick = tick;<br>
return;<br>
}<br>
<br>
diffTick = tick - lastTick;<br>
<br>
if (level != PI_TIMEOUT) lastTick = tick;<br>
<br>
updateState(&activeHigh, level, diffTick);<br>
updateState(&activeLow, level, diffTick);<br>
}<br>
<br>
void updateState(decode_t * decode, int level, uint32_t micros)<br>
{<br>
/*<br>
We are dealing with active high as
well as active low<br>
remotes. Abstract the common
functionality.<br>
*/<br>
<br>
if (decode->state == OUTSIDE_CODE)<br>
{<br>
if (level == decode->level)<br>
{<br>
if (micros >
MIN_MESSAGE_GAP)<br>
{<br>
decode->state = INSIDE_CODE;<br>
decode->count = 0;<br>
}<br>
}<br>
}<br>
else<br>
{<br>
if (micros > MAX_MESSAGE_END)<br>
{<br>
/* end of message
*/<br>
<br>
/* ignore if last
code not consumed */<br>
<br>
if (!ir_hash)
ir_hash = getHash(decode);<br>
<br>
decode->state =
OUTSIDE_CODE;<br>
}<br>
else<br>
{<br>
if
(decode->count < (MAX_TRANSITIONS-1))<br>
{<br>
if (level != PI_TIMEOUT)<br>
decode->micros[decode->count++] = micros;<br>
}<br>
}<br>
}<br>
}<br>
<br>
int compare(unsigned int oldval, unsigned int newval)<br>
{<br>
if (newval < (oldval
* 0.75)) {return 1;}<br>
else if (oldval < (newval * 0.75)) {return 2;}<br>
else
{return 4;}<br>
}<br>
<br>
uint32_t getHash(decode_t * decode)<br>
{<br>
/* use FNV-1a */<br>
<br>
uint32_t hash;<br>
int i, value;<br>
<br>
if (decode->count < 6) {return 0;}<br>
<br>
hash = FNV_BASIS_32;<br>
<br>
for (i=0; i<(decode->count-2); i++)<br>
{<br>
value =
compare(decode->micros[i], decode->micros[i+2]);<br>
<br>
hash = hash ^ value;<br>
hash = (hash * FNV_PRIME_32);<br>
}<br>
<br>
return hash;<br>
}<br></code>
<h3>BUILD</h3>
<code>cc -o ir_remote ir_remote.c -lpigpio -lrt
-lpthread<br></code>
<h3>RUN</h3>
<code>sudo ./ir_remote</code><br>
<p>A hash code is formed from the level transitions detected during
a remote key press. This is likely to be unique over multiple
remotes and keys.</p>
<p>While the program is running you can capture the waveform using
the notification feature built in to pigpio. Issue the
following commands on the Pi.</p>
<code>pigs no<br>
pig2vcd </dev/pigpio0 >ir.vcd &<br>
pigs nb 0 0x80 # set bits for gpios 7 (0x80)<br></code>
<p>Press a few different remotes and keys. Then enter<br></p>
<code>pigs nc 0</code><br>
<p>The file ir.vcd will contain the captured waveform, which can be
viewed using GTKWave.</p>
<p>Overview</p>
<img src="images/ir-wave-1.png" style=
"width: 600px; height: 100px;" alt="ir remote waveform 1"><br>
<p>Remote A typical waveform</p>
<img src="images/ir-wave-2.png" style=
"width: 600px; height: 100px;" alt="ir remote waveform 2"><br>
<p>Remote B typical waveform</p>
<img style="width: 600px; height: 100px;" alt=
"ir remote waveform 3" src="images/ir-wave-3.png">
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<td style="width: 200px"><div style="text-align: left;"><small>© 2012-2020</small></div></td>
<td style="width: 350px"><div style="text-align: center;">e-mail: pigpio @ abyz.me.uk</div></td>
<td style="width: 200px"><div style="text-align: right;"><small>Updated: 30/04/2020</small></div></td>
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