mirror of https://github.com/joan2937/pigpio
245 lines
8.1 KiB
Plaintext
245 lines
8.1 KiB
Plaintext
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<p>The following code shows one way to read an infrared remote
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control device (the sort used in TVs and stereo systems).</p>
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<h3>SETUP</h3>
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<img alt="fritzing diagram" style="width: 200px; height: 317px;"
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src="images/ir-fritz.png" align="left" hspace="10">The device used
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is a <span itemprop="name">SFH5110 (IR Receiver for remote control,
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carrier 38 kHz).<br>
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<br></span> Pin 1 (left from front) may be connected to any spare
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gpio. Here it's connected via a 4K7 current limiting
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resistor. This isn't really needed as the device has an
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internal 23K resistor in-line. It does no harm though.<br>
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<br>
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Pin 2 should be connected to a Pi ground pin.<br>
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<br>
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Pin 3 should be connected to a Pi 5V pin.<br>
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<p>Here pin 1 to gpio7 (P1-26) via a 4K7 resistor, pin 2 to ground
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(P1-14), and pin 3 to 5V (P1-2).<br clear="all"></p>
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<p><img src="images/ir-photo.jpg" style=
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"width: 500px; height: 500px;" alt="photo of set-up"></p>
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<h3>CODE</h3>
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<code>#include <stdio.h><br>
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<br>
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#include <pigpio.h><br>
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<br>
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#define IR_PIN 7<br>
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<br>
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#define OUTSIDE_CODE 0<br>
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#define INSIDE_CODE 1<br>
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<br>
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#define MIN_MESSAGE_GAP 3000<br>
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#define MAX_MESSAGE_END 3000<br>
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<br>
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#define MAX_TRANSITIONS 500<br>
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<br>
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/*<br>
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using the FNV-1a
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hash <br>
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from
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http://isthe.com/chongo/tech/comp/fnv/#FNV-param<br>
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*/<br>
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<br>
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#define FNV_PRIME_32 16777619<br>
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#define FNV_BASIS_32 2166136261U<br>
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<br>
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static volatile uint32_t ir_hash = 0;<br>
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<br>
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typedef struct<br>
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{<br>
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int state;<br>
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int count;<br>
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int level;<br>
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uint16_t micros[MAX_TRANSITIONS];<br>
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} decode_t;<br>
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<br>
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/* forward declarations */<br>
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<br>
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void alert(int gpio, int level, uint32_t
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tick);<br>
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uint32_t getHash(decode_t * decode);<br>
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void updateState(decode_t * decode, int
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level, uint32_t micros);<br>
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<br>
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int main(int argc, char * argv[])<br>
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{<br>
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if (gpioInitialise()<0)<br>
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{<br>
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return 1 ;<br>
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}<br>
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<br>
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/* IR pin as input */<br>
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<br>
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gpioSetMode(IR_PIN, PI_INPUT);<br>
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<br>
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/* 5ms max gap after last pulse */<br>
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<br>
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gpioSetWatchdog(IR_PIN, 5);<br>
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<br>
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/* monitor IR level changes */<br>
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<br>
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gpioSetAlertFunc(IR_PIN, alert);<br>
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<br>
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while (1)<br>
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{<br>
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if (ir_hash)<br>
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{<br>
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/* non-zero means
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new decode */<br>
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printf("ir code is
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%u\ ", ir_hash);<br>
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ir_hash = 0;<br>
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}<br>
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<br>
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gpioDelay(100000); /* check remote
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10 times per second */<br>
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}<br>
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<br>
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gpioTerminate();<br>
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}<br>
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<br>
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void alert(int gpio, int level, uint32_t tick)<br>
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{<br>
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static int inited = 0;<br>
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<br>
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static decode_t activeHigh, activeLow;<br>
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<br>
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static uint32_t lastTick;<br>
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<br>
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uint32_t diffTick;<br>
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<br>
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if (!inited)<br>
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{<br>
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inited = 1;<br>
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<br>
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activeHigh.state = OUTSIDE_CODE;
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activeHigh.level = PI_LOW;<br>
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activeLow.state =
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OUTSIDE_CODE; activeLow.level = PI_HIGH;<br>
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<br>
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lastTick = tick;<br>
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return;<br>
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}<br>
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<br>
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diffTick = tick - lastTick;<br>
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<br>
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if (level != PI_TIMEOUT) lastTick = tick;<br>
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<br>
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updateState(&activeHigh, level, diffTick);<br>
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updateState(&activeLow, level, diffTick);<br>
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}<br>
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<br>
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void updateState(decode_t * decode, int level, uint32_t micros)<br>
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{<br>
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/*<br>
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We are dealing with active high as
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well as active low<br>
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remotes. Abstract the common
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functionality.<br>
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*/<br>
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<br>
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if (decode->state == OUTSIDE_CODE)<br>
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{<br>
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if (level == decode->level)<br>
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{<br>
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if (micros >
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MIN_MESSAGE_GAP)<br>
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{<br>
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decode->state = INSIDE_CODE;<br>
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decode->count = 0;<br>
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}<br>
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}<br>
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}<br>
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else<br>
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{<br>
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if (micros > MAX_MESSAGE_END)<br>
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{<br>
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/* end of message
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*/<br>
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<br>
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/* ignore if last
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code not consumed */<br>
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<br>
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if (!ir_hash)
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ir_hash = getHash(decode);<br>
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<br>
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decode->state =
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OUTSIDE_CODE;<br>
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}<br>
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else<br>
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{<br>
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if
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(decode->count < (MAX_TRANSITIONS-1))<br>
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{<br>
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if (level != PI_TIMEOUT)<br>
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decode->micros[decode->count++] = micros;<br>
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}<br>
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}<br>
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}<br>
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}<br>
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<br>
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int compare(unsigned int oldval, unsigned int newval)<br>
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{<br>
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if (newval < (oldval
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* 0.75)) {return 1;}<br>
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else if (oldval < (newval * 0.75)) {return 2;}<br>
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else
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{return 4;}<br>
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}<br>
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<br>
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uint32_t getHash(decode_t * decode)<br>
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{<br>
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/* use FNV-1a */<br>
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<br>
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uint32_t hash;<br>
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int i, value;<br>
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<br>
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if (decode->count < 6) {return 0;}<br>
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<br>
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hash = FNV_BASIS_32;<br>
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<br>
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for (i=0; i<(decode->count-2); i++)<br>
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{<br>
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value =
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compare(decode->micros[i], decode->micros[i+2]);<br>
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<br>
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hash = hash ^ value;<br>
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hash = (hash * FNV_PRIME_32);<br>
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}<br>
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<br>
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return hash;<br>
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}<br></code>
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<h3>BUILD</h3>
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<code>cc -o ir_remote ir_remote.c -lpigpio -lrt
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-lpthread<br></code>
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<h3>RUN</h3>
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<code>sudo ./ir_remote</code><br>
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<p>A hash code is formed from the level transitions detected during
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a remote key press. This is likely to be unique over multiple
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remotes and keys.</p>
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<p>While the program is running you can capture the waveform using
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the notification feature built in to pigpio. Issue the
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following commands on the Pi.</p>
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<code>pigs no<br>
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pig2vcd </dev/pigpio0 >ir.vcd &<br>
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pigs nb 0 0x80 # set bits for gpios 7 (0x80)<br></code>
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<p>Press a few different remotes and keys. Then enter<br></p>
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<code>pigs nc 0</code><br>
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<p>The file ir.vcd will contain the captured waveform, which can be
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viewed using GTKWave.</p>
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<p>Overview</p>
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<img src="images/ir-wave-1.png" style=
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"width: 600px; height: 100px;" alt="ir remote waveform 1"><br>
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<p>Remote A typical waveform</p>
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<img src="images/ir-wave-2.png" style=
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"width: 600px; height: 100px;" alt="ir remote waveform 2"><br>
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<p>Remote B typical waveform</p>
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<img style="width: 600px; height: 100px;" alt=
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"ir remote waveform 3" src="images/ir-wave-3.png">
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