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diff --git a/DOC/src/html/ex_sonar_ranger.html b/DOC/src/html/ex_sonar_ranger.html new file mode 100644 index 0000000..8edb9c2 --- /dev/null +++ b/DOC/src/html/ex_sonar_ranger.html @@ -0,0 +1,164 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> +<html> +<head> +<meta name="generator" content="Bluefish 2.2.10" > +<meta content="text/html; charset=utf-8" http-equiv="Content-Type"> +<title>Sonar ranger example</title> +</head> +<body> +<p>The following code shows a method of reading a class of sonar +rangers. These rangers requires a trigger pulse. +Shortly after receiving a trigger they transmit a noise pulse and +set the echo line high. When the echo is received the echo +line is set low.<br></p> +<h3>SETUP</h3> +<img src="images/son-fritz.png" alt="fritzing diagram" style= +"width: 200px; height: 600px;" align="left" hspace="10"><br> +<br> +<br> +<br> +<br> +The ranger used is a SRF05 (check the pinouts, there are many +variants).<br> +<br> +The fritzing diagram shows the back of the ranger, i.e. pin 1 is +the rightmost.<br> +<br> +Pin 1 is 5V.<br> +Pin 2 is the trigger line.<br> +Pin 3 is the echo line.<br> +Pin 4 is out (unused).<br> +Pin 5 is ground.<br> +<br clear="all"> +<p><img src="images/son-photo.jpg" style= +"width: 500px; height: 376px;" alt="photo of set-up"></p> +<h3>CODE</h3> +<code>#include <stdio.h><br> +<br> +#include <pigpio.h><br> +<br> +/*<br> +<br> +P1 Name gpio used for<br> +<br> + 2 5V --- +5V<br> + 6 GND --- +Ground<br> +24 CE0 8 +Sonar echo<br> +26 CE1 7 +Sonar trigger<br> +<br> +*/<br> +<br> +#define SONAR_TRIGGER 7<br> +#define SONAR_ECHO 8<br> +<br> +/* forward prototypes */<br> +<br> +void sonarTrigger(void);<br> +<br> +void sonarEcho(int gpio, int level, uint32_t tick);<br> +<br> +int main(int argc, char *argv[])<br> +{<br> + if (gpioInitialise()<0) return 1;<br> +<br> + gpioSetMode(SONAR_TRIGGER, PI_OUTPUT);<br> + gpioWrite (SONAR_TRIGGER, PI_OFF);<br> +<br> + gpioSetMode(SONAR_ECHO, +PI_INPUT);<br> +<br> + /* update sonar 20 times a second, timer #0 */<br> +<br> + gpioSetTimerFunc(0, 50, sonarTrigger); /* every 50ms +*/<br> +<br> + /* monitor sonar echos */<br> +<br> + gpioSetAlertFunc(SONAR_ECHO, sonarEcho);<br> +<br> + while (1) sleep(1);<br> +<br> + gpioTerminate();<br> +<br> + return 0;<br> +}<br> +<br> +void sonarTrigger(void)<br> +{<br> + /* trigger a sonar reading */<br> +<br> + gpioWrite(SONAR_TRIGGER, PI_ON);<br> +<br> + gpioDelay(10); /* 10us trigger pulse */<br> +<br> + gpioWrite(SONAR_TRIGGER, PI_OFF);<br> +}<br> +<br> +void sonarEcho(int gpio, int level, uint32_t tick)<br> +{<br> + static uint32_t startTick, firstTick=0;<br> +<br> + int diffTick;<br> +<br> + if (!firstTick) firstTick = tick;<br> +<br> + if (level == PI_ON)<br> + {<br> + startTick = tick;<br> + }<br> + else if (level == PI_OFF)<br> + {<br> + diffTick = tick - startTick;<br> +<br> + printf("%u %u\ ", tick-firstTick, +diffTick);<br> + }<br> +}<br></code> +<h3>BUILD</h3> +<code>cc -o sonar sonar.c -lpigpio -lrt -lpthread<br></code> +<h3>RUN</h3> +<code>sudo ./sonar >sonar.dat &</code><br> +<br> +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.<br> +<br> +<code>pigs no<br> +pig2vcd </dev/pigpio0 >sonar.vcd &<br> +pigs nb 0 0x180 # set bits for gpios 7 and 8<br></code> +<p>Move an object in front of the sonar ranger for a few +seconds.<br></p> +<code>pigs nc 0</code><br> +<p>The file sonar.vcd will contain the captured waveform, which can +be viewed using GTKWave.</p> +<p>Overview</p> +<img src="images/son-wave-1.png" style= +"width: 600px; height: 100px;" alt="LDR waveform 1"><br> +<p>Reading circa every 10ms<br></p> +<img src="images/son-wave-2.png" style= +"width: 600px; height: 100px;" alt="Sonar waveform 2"><br> +<p>One reading, circa 400us<br></p> +<img src="images/son-wave-3.png" style= +"width: 600px; height: 100px;" alt="Sonar waveform 3"><br> +<p>another</p> +<img style="width: 600px; height: 100px;" alt="Sonar waveform 4" +src="images/son-wave-4.png"><br> +<p>The file sonar.dat will contain pairs of timestamps and echo +length (in us). The following script will convert the +timestamps into seconds.<span style= +"font-style: italic;"><br></span></p> +<p><code>awk '{print $1/1000000, $2}' sonar.dat +>sonar-secs.dat</code></p> +<p>Gnuplot is a useful tool to graph data.<br></p> +plot 'sonar-secs.dat' title 'Sonar'<br> +<p><img src="images/son-gnup-1.png" style= +"width: 600px; height: 321px;" alt="gnuplot 1"><br> + plot [10:25] 'sonar-secs.dat' title 'Sonar'<br></p> +<p><img src="images/son-gnup-2.png" style= +"width: 600px; height: 321px;" alt="gnuplot 1"></p> +</body> +</html> |