Revision: 1333 Author: sebastien.lelong Date: Sat Sep 19 14:18:54 2009 Log: first draft for DITA documents: tutorials book http://code.google.com/p/jallib/source/detail?r=1333
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There are many different references, depending on the beam pattern, the minimal and maximal distance you want to be able to get, etc... The way you got results also make a difference: either <b>analog</b> (you'll get a voltage proportional to the distance), or <b>digital</b> (you'll directly get a digital value). This nice article will explain these details (and now I know GP2D02 seems to be discontinued...)</abstract> + <prolog> + <author>Sébastien Lelong</author> + <publisher>Jallib Group</publisher> + <copyright> + <copyryear year="2009"/> + <copyrholder>Jallib Group</copyrholder> + </copyright> + </prolog> + <body> + <section> + <title>Overview of GP2D02 IR ranger</title> + <p>GP2D02 IR ranger is able to measure distances between approx. 10cm and 1m. Results are available as digital values you can access through a dedicated protocol. One pin, Vin, will be used to act on the ranger. Another pin, Vout, will be read to determine the distance. Basically, getting a distance involves the following:</p> + <p><ol> + <li>First you wake up the ranger and tell it to perform a distance measure</li> + <li>Then, for each bit, you read Vout in order to reconstitute the whole byte, that is, the distance</li> + <li>finally, you switch off the ranger</li> + </ol>The following timing chart taken from the datasheet will explain this better.</p> + <fig> + <title>GD2D02 IR ranger : timing chart</title> + <image href="images/timingchart.jpg" width="400" placement="break"/> + </fig> + <note>the distances obtained from the ranger aren't linear, you'll need some computation to make them so.</note> + <p><b>Sharp GP2D02 IR ranger</b> looks like this:</p> + <image href="images/wires.jpg" width="400"/> + <p><ul> + <li><i>Red</i> wire is for +5V</li> + <li><i>Black</i> wire ground</li> + <li><i>Green</i> wire is for Vin pin, used to control the sensor</li> + <li><i>Yellow</i> wire is for Vout pin, from which 8-bits results read</li> + </ul><i>(make a mental note of this...)</i></p> + </section> + <section> + <title>Interfacing the Sharp GP2D02 IR ranger</title> + <p>Interfacing such a sensor is quite straight forward. The only critical point is <b>Vin</b> ranger pin can't handle high logic level of the PIC's output, <i>this level mustn't exceed 3.3 volts</i>. A <b>zener diode</b> can be used to limit this level.</p> + <note>be careful while connecting this diode. Don't forget it, and don't put it in the wrong side. You may damage your sensor. And I'm not responsible for ! You've been warned... That's said, I already forgot it, put it in the wrong side, and thought I'd killed my GP2D02, but this one always got back to life. Anyway, be cautious !</note> + <p>Here's the whole schematic. The goal here is to collect data from the sensor, and light up a LED, more or less according to the read distance. That's why we'll use a LED driven by PWM.</p> + <fig> + <title>Interfacing Sharp GP2D02 IR range : schematic</title> + <image href="images/gp2d02_schematics.png"/> + </fig> + <p>Here's the ranger with the diode soldered on the green wire (which is Vin pin, using your previously created mental note...):</p> + <image href="images/diode.jpg" width="400" placement="break"/> + <p>I've also added thermoplastic rubber tubes, to cleanly join all the wires:</p> + <image href="images/cable.jpg" width="400" placement="break"/> + <p>Finally, in order to easily plug/unplug the sensor, I've soldered nice polarized connectors:</p> + <image href="images/connectors.jpg" width="400" placement="break"/> + </section> + <section> + <title>Writing the program</title> + <p>jallib >=0.3 contains a library, <xref href="http://code.google.com/p/jallib/source/browse/trunk/include/external/ranger/ir/ir_ranger_gp2d02.jal"; format="html">ir_ranger_gp2d02.jal</xref>, used to handle this kind of rangers. The setup is quite straight forward: just declare your Vin and Vout pins, and pass them to the <codeph>gp2d02_read_pins()</codeph>. This function returns the distance as a raw value. Directly passing pins allows you to have multiple rangers of this type (many robots have many of them arranged in the front and back sides, to detect and avoid obstacles).</p> + <p>Using PWM libs, we can easily make our LED more or less bright. In the mean time, we'll also transmit the results through a serial link.</p> + <codeblock>var volatile bit gp2d02_vin is pin_a4 +var volatile bit gp2d02_vout is pin_a6 +var bit gp2d02_vin_direction is pin_a4_direction +var bit gp2d02_vout_direction is pin_a6_direction +include ir_ranger_gp2d02 +-- set pin direction (careful: "vin" is the GP2D02 pin's name, +-- it's an input for GP2D02, but an output for PIC !) +gp2d02_vin_direction = output +gp2d02_vout_direction = input + +var byte measure +forever loop + -- read distance from ranger num. 0 + measure = gp2d02_read_pins(gp2d02_vin,gp2d02_vout) + -- results via serial + serial_hw_write(measure) + -- now blink more or less + pwm1_set_dutycycle(measure) +end loop</codeblock> + <note>I could directly pass <codeph>pin_A4</codeph> and <codeph>pin_A6</codeph>, but to avoid confusion, I prefer using <i>aliases</i>.</note> + <p>A sample, <xref href="http://code.google.com/p/jallib/source/browse/trunk/sample/16f88_ir_ranger_gp2d02.jal"; format="html">16f88_ir_ranger_gp2d02.jal</xref>, is available in <xref href="http://code.google.com/p/jallib/source/browse/trunk/include/external/ranger/ir/ir_ranger_gp2d02.jal"; format="html">jallib SVN repository</xref>jallib released packages, and also in , starting from version 0.3. You can access downloads <xref href="http://code.google.com/p/jallib/downloads/list"; format="html">here</xref>.</p> + </section> + <section> + <title>Building the whole on a breadboard</title> + <p>Building the whole on a breadboard<image href="images/circuit.jpg" width="400" placement="break"/></p> + <p>I usually power two tracks on the side, used for the PIC and for the ranger:<image href="images/circuit_ranger.jpg" width="400" placement="break"/></p> + <p>Using the same previously created mental note, I connected the yellow Vout pin using a yellow wire, and the green Vin pin using a green wire...<image href="images/circuit_pic.jpg" width="400" placement="break"/></p> + </section> + <section> + <title>Testing (and the video)</title> + <p>Time to test this nice circuit ! Power the whole, and check no smoke is coming from the PIC or (and) the ranger. Now get an object, like you hand, more or less closed to the ranger and observe the LED, or the serial output... Sweet !</p> + <p><xref href="http://www.youtube.com/watch?v=l5AZwv7LzyM"; format="html">http://www.youtube.com/watch?v=l5AZwv7LzyM</xref></p> + <p><i>Sébastien Lelong</i></p> + </section> + </body> +</topic> ======================================= --- /dev/null +++ /trunk/doc/dita/tutorials/tutorials.ditamap Sat Sep 19 14:18:54 2009 @@ -0,0 +1,27 @@ +<?xml version='1.0' encoding='UTF-8'?> +<!-- This document was created with Syntext Serna Free. --><!DOCTYPE bookmap PUBLIC "-//OASIS//DTD DITA BookMap//EN" "bookmap.dtd" []> +<bookmap id="bookmap_tutorials"> + <booktitle> + <mainbooktitle>The Tutorial Book</mainbooktitle> + <booktitlealt>Have fun with PIC microcontrollers,Jal v2 and Jallib</booktitlealt> + </booktitle> + <bookmeta> + <author>Sébastien Lelong</author> + <bookrights> + <copyrfirst> + <year>2009</year> + </copyrfirst> + <bookowner> + <organization>Jallib Group</organization> + </bookowner> + </bookrights> + </bookmeta> + <frontmatter> + <booklists> + <toc/> + </booklists> + </frontmatter> + <chapter> + <topicref href="tutorial_gp2d02.xml"/> + </chapter> +</bookmap> --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "jallib" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/jallib?hl=en -~----------~----~----~----~------~----~------~--~---
