2020-04-30 06:43:20 +02:00
< !DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
< html xmlns = "http://www.w3.org/1999/xhtml" xml:lang = "en" lang = "en" >
< head >
< meta name = "description" content = "Raspberry Pi Reg. C GPIO library and Python GPIO module and shell command utilities to control the GPIO, including SPI, I2C, and serial links." / >
< meta name = "keywords" content = "raspberry, pi, C, Python, GPIO, library, shell, command, utilities, module, SPI, I2C, serial" / >
< meta http-equiv = "Content-Type" content = "text/html;charset=utf-8" / >
< title > pigpio library< / title >
< link rel = "stylesheet" type = "text/css" href = "scripts/index.css" >
< link rel = "icon" href = "favicon.ico" type = "image/x-icon" >
< link rel = "shortcut icon" href = "favicon.ico" type = "image/x-icon" >
< / head >
< body >
< table style = "padding:0px; border:0px; margin:0px; width:780px; background-color:#e0e0e0;" >
< td style = "background:#EAF2E6 url('images/sidebar.gif') repeat-y; width:35px; height:100%" > < / td >
< td >
< table >
< div style = "background:url('images/topbar.gif') repeat-x; height: 70px; font-size:1.5em; vertical-align: top;" > < a href = "index.html" > < img src = "images/pigpio-logo.gif" border = "0" / > < / a > pigpio library< / div >
< / table >
< table > < div >
< 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 >
< / div > < / table >
< table >
< td style = "vertical-align: top; background-color: #98bf21;" > < a class = "l1" href = "index.html" > pigpio< / a >
< a class = "l1" href = "cif.html" > pigpio C I/F< / a >
< a class = "l1" href = "pigpiod.html" > pigpiod< / a >
< a class = "l1" href = "pdif2.html" > pigpiod C I/F< / a >
< a class = "l1" href = "python.html" > Python< / a >
< a class = "l1" href = "pigs.html" > pigs< / a >
< a class = "l1" href = "piscope.html" > piscope< / a >
< a class = "l1" href = "misc.html" > Misc< / a >
< a class = "l1" href = "examples.html" > Examples< / a >
< a class = "l1" href = "download.html" > Download< / a >
< a class = "l1" href = "faq.html" > FAQ< / a >
< a class = "l1" href = "sitemap.html" > Site Map< / a >
< / td >
< 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">
< / td >
< / table >
< div style = "vertical-align: center; text-align: center; background-color:#98bf21; font-size:0.8em; height:30px" > < a class = "l2" href = "index.html" > [pigpio]< / a >
< a class = "l2" href = "cif.html" > [pigpio C I/F]< / a >
< a class = "l2" href = "pigpiod.html" > [pigpiod]< / a >
< a class = "l2" href = "pdif2.html" > [pigpiod C I/F]< / a >
< a class = "l2" href = "python.html" > [Python]< / a >
< a class = "l2" href = "pigs.html" > [pigs]< / a >
< a class = "l2" href = "piscope.html" > [piscope]< / a >
< a class = "l2" href = "misc.html" > [Misc]< / a >
< a class = "l2" href = "examples.html" > [Examples]< / a >
< a class = "l2" href = "download.html" > [Download]< / a >
< a class = "l2" href = "faq.html" > [FAQ]< / a >
< a class = "l2" href = "sitemap.html" > [Site Map]< / a >
< / div >
< table > < tr >
< 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 >
2020-04-30 16:55:43 +02:00
< td style = "width: 200px" > < div style = "text-align: right;" > < small > Updated: 30/04/2020< / small > < / div > < / td >
2020-04-30 06:43:20 +02:00
< / tr > < / table >
< / td >
< / table >
< / body >
< / html >
