https://community.element14.com/challenges-projects/element14-presents/project-videos/w/documents/28140/charlieplexing-buttons-and-leds-at-the-same-time---how-hard-can-it-be----episode-604en-USTelligent Community 12https://community.element14.com/challenges-projects/element14-presents/project-videos/w/documents/28140/charlieplexing-buttons-and-leds-at-the-same-time---how-hard-can-it-be----episode-604Fri, 26 May 2023 07:24:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:a8a4d15d-6ca1-44b3-bb39-66e6b71b4b96Matthttps://community.element14.com/challenges-projects/element14-presents/project-videos/w/documents/28140/charlieplexing-buttons-and-leds-at-the-same-time---how-hard-can-it-be----episode-604#commentsCurrent Revision posted to Documents by Matt on 5/26/2023 7:24:00 AM<br /> <p>So many buttons so little IO. When you want to drive a large number of LEDs or read buttons the obvious choice is multiplexing them. But there is a method called charlieplexing that lets you use even more LEDs and buttons with even less IO pins. Clem wants to interface a large amount of buttons and LEDs with a microcontroller but has a limited number of pins.&nbsp; &nbsp;He&#39;s also trying to save money on parts. Could you just replace expensive signal diodes with cheap LEDs? Could you use the same pins to read buttons and drive LEDs in the same matrix? Could you also achieve true n-key rollover without having a diode on every single button? How hard can it be?</p> <h3 id="mcetoc_1h03bofrk0">Watch the Video:</h3> <p><a href="https://www.youtube.com/watch?v=6R3AN3pvo-k">www.youtube.com/watch</a></p> <h3 id="mcetoc_1h03bsfpu3">Bonus Content:</h3> <ul> <li><a href="/challenges-projects/element14-presents/m/files/147593" data-e14adj="t">Login to Download the Code!</a></li> </ul> <h3 id="mcetoc_1h03bqutc1">Bill of Material:</h3> <table class="e14-product-bom-main"> <tbody> <tr> <th>Product Name</th> <th>Manufacturer</th> <th>Quantity</th> <th><a id="e14-product-link-2d751" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=3780506~9,2212779,2770338,2503749&nsku=29AK2184~9,45W6205,24AC5053,71Y9192&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_BUY_KIT" class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('2d751'));" data-farnell="3780506~9,2212779,2770338,2503749" data-newark="29AK2184~9,45W6205,24AC5053,71Y9192" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined~9,,," data-avnetema="undefined~9,,," data-avnetasia="undefined~9,,," >Buy Kit</a> </th> </tr> <tr> <td>LED, Super Red, Through Hole, T-1 3/4 (5mm), 12 mA, 5 V, 640 nm</td> <td>Multicomp</td> <td>9</td> <td><a id="e14-product-link-0e6cc" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=3780506&nsku=29AK2184&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('0e6cc'));" data-farnell="3780506" data-newark="29AK2184" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Arduino Mega 2560, ATmega2560, 54 I/O, 256KB Flash, 8KB SRAM, 4KB EEPROM</td> <td>Arduino</td> <td>1</td> <td><a id="e14-product-link-d0f5c" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2212779&nsku=45W6205&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('d0f5c'));" data-farnell="2212779" data-newark="45W6205" data-comoverride="" data-cmpoverride="" data-cpc="SC13721" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Jumper Wire Kit, Multicolour, 2 mm - 125 mm, 22 AWG, 140 Piece</td> <td>Multicomp</td> <td>1</td> <td><a id="e14-product-link-0012a" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2770338&nsku=24AC5053&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('0012a'));" data-farnell="2770338" data-newark="24AC5053" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Breadboard, Mounted, 1580 Pin, 10mm, x 135mm</td> <td>Multicomp</td> <td>1</td> <td><a id="e14-product-link-2a886" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2503749&nsku=71Y9192&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('2a886'));" data-farnell="2503749" data-newark="71Y9192" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr class="xs-hide"> <td>&nbsp;</td> <td></td> <td></td> <td></td> </tr> </tbody> </table> <p></p> <div style="background:#ffffff;border:1px solid #dadada;margin:0;padding:14px 16px 16px 18px;vertical-align:top;"> <div style="display:inline-block;float:left;padding:0px 25px 8px 0px;"><a href="/challengesprojects/element14-presents/" data-e14adj="t"><img alt="element14 presents" src="/e14/assets/legacy/2018/e14PresentsJune818.png" width="180px" /></a></div> <div style="display:inline-block;vertical-align:top;width:70%;"></div> <div style="display:inline-block;vertical-align:top;width:70%;"><br /> <p style="margin:0;"><span><a class="jivecontainerTT-hover-container jive-link-community-small" href="/challengesprojects/element14-presents/" data-e14adj="t">element14 presents</a></span>&nbsp; <strong>|</strong>&nbsp; <a class="jive-link-wiki-small" href="/challenges-projects/element14-presents/vcp-program/w/documents/3692/vcp-biography-clem" data-e14adj="t">About Clem</a>&nbsp; <strong>|</strong>&nbsp; <a class="jivecontainerTT-hover-container jive-link-community-small" href="/challengesprojects/element14-presents/project-videos/" data-e14adj="t">Project Videos</a></p> </div> </div><div style="clear:both;"></div> <div style="font-size: 90%;">Tags: buttons, keyboard, multiplexing, leds, Charlieplexing, arduino, friday_release, arduino mega, e14p_CMM</div> https://community.element14.com/challenges-projects/element14-presents/project-videos/w/documents/28140/charlieplexing-buttons-and-leds-at-the-same-time---how-hard-can-it-be----episode-604/revision/6Fri, 26 May 2023 16:25:34 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:a8a4d15d-6ca1-44b3-bb39-66e6b71b4b96pchanhttps://community.element14.com/challenges-projects/element14-presents/project-videos/w/documents/28140/charlieplexing-buttons-and-leds-at-the-same-time---how-hard-can-it-be----episode-604#commentsRevision 6 posted to Documents by pchan on 5/26/2023 4:25:34 PM<br /> <p>So many buttons so little IO. When you want to drive a large number of LEDs or read buttons the obvious choice is multiplexing them. But there is a method called charlieplexing that lets you use even more LEDs and buttons with even less IO pins. Clem wants to interface a large amount of buttons and LEDs with a microcontroller but has a limited number of pins.&nbsp; &nbsp;He&#39;s also trying to save money on parts. Could you just replace expensive signal diodes with cheap LEDs? Could you use the same pins to read buttons and drive LEDs in the same matrix? Could you also achieve true n-key rollover without having a diode on every single button? How hard can it be?</p> <h3 id="mcetoc_1h03bofrk0">Watch the Video:</h3> <p><a href="https://www.youtube.com/watch?v=6R3AN3pvo-k">www.youtube.com/watch</a></p> <h3 id="mcetoc_1h03bsfpu3">Bonus Content:</h3> <ul> <li><a href="/challenges-projects/element14-presents/m/files/147593">Login to Download the Code!</a></li> </ul> <h3 id="mcetoc_1h03bqutc1">Bill of Material:</h3> <table class="e14-product-bom-main"> <tbody> <tr> <th>Product Name</th> <th>Manufacturer</th> <th>Quantity</th> <th><a id="e14-product-link-afdea" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=3780506~9,2212779,2770338,2503749&nsku=29AK2184~9,45W6205,24AC5053,71Y9192&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_BUY_KIT" class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('afdea'));" data-farnell="3780506~9,2212779,2770338,2503749" data-newark="29AK2184~9,45W6205,24AC5053,71Y9192" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined~9,,," data-avnetema="undefined~9,,," data-avnetasia="undefined~9,,," >Buy Kit</a> </th> </tr> <tr> <td>LED, Super Red, Through Hole, T-1 3/4 (5mm), 12 mA, 5 V, 640 nm</td> <td>Multicomp</td> <td>9</td> <td><a id="e14-product-link-b8402" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=3780506&nsku=29AK2184&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('b8402'));" data-farnell="3780506" data-newark="29AK2184" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Arduino Mega 2560, ATmega2560, 54 I/O, 256KB Flash, 8KB SRAM, 4KB EEPROM</td> <td>Arduino</td> <td>1</td> <td><a id="e14-product-link-5e5dd" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2212779&nsku=45W6205&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('5e5dd'));" data-farnell="2212779" data-newark="45W6205" data-comoverride="" data-cmpoverride="" data-cpc="SC13721" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Jumper Wire Kit, Multicolour, 2 mm - 125 mm, 22 AWG, 140 Piece</td> <td>Multicomp</td> <td>1</td> <td><a id="e14-product-link-915d7" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2770338&nsku=24AC5053&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('915d7'));" data-farnell="2770338" data-newark="24AC5053" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Breadboard, Mounted, 1580 Pin, 10mm, x 135mm</td> <td>Multicomp</td> <td>1</td> <td><a id="e14-product-link-7ebb3" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2503749&nsku=71Y9192&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('7ebb3'));" data-farnell="2503749" data-newark="71Y9192" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr class="xs-hide"> <td>&nbsp;</td> <td></td> <td></td> <td></td> </tr> </tbody> </table> <p></p> <div style="background:#ffffff;border:1px solid #dadada;margin:0;padding:14px 16px 16px 18px;vertical-align:top;"> <div style="display:inline-block;float:left;padding:0px 25px 8px 0px;"><a href="/challengesprojects/element14-presents/"><img alt="element14 presents" src="/e14/assets/legacy/2018/e14PresentsJune818.png" width="180px" /></a></div> <div style="display:inline-block;vertical-align:top;width:70%;"></div> <div style="display:inline-block;vertical-align:top;width:70%;"><br /> <p style="margin:0;"><span><a class="jivecontainerTT-hover-container jive-link-community-small" href="/challengesprojects/element14-presents/">element14 presents</a></span>&nbsp; <strong>|</strong>&nbsp; <a class="jive-link-wiki-small" href="/challenges-projects/element14-presents/vcp-program/w/documents/3692/vcp-biography-clem">About Clem</a>&nbsp; <strong>|</strong>&nbsp; <a class="jivecontainerTT-hover-container jive-link-community-small" href="/challengesprojects/element14-presents/project-videos/">Project Videos</a></p> </div> </div><div style="clear:both;"></div> <div style="font-size: 90%;">Tags: buttons, keyboard, multiplexing, leds, Charlieplexing, arduino, friday_release, arduino mega, e14p_CMM</div> https://community.element14.com/challenges-projects/element14-presents/project-videos/w/documents/28140/charlieplexing-buttons-and-leds-at-the-same-time---how-hard-can-it-be----episode-604/revision/5Fri, 26 May 2023 14:00:43 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:a8a4d15d-6ca1-44b3-bb39-66e6b71b4b96pchanhttps://community.element14.com/challenges-projects/element14-presents/project-videos/w/documents/28140/charlieplexing-buttons-and-leds-at-the-same-time---how-hard-can-it-be----episode-604#commentsRevision 5 posted to Documents by pchan on 5/26/2023 2:00:43 PM<br /> <p>So many buttons so little IO. When you want to drive a large number of LEDs or read buttons the obvious choice is multiplexing them. But there is a method called charlieplexing that lets you use even more LEDs and buttons with even less IO pins. Clem wants to interface a large amount of buttons and LEDs with a microcontroller but has a limited number of pins.&nbsp; &nbsp;He&#39;s also trying to save money on parts. Could you just replace expensive signal diodes with cheap LEDs? Could you use the same pins to read buttons and drive LEDs in the same matrix? Could you also achieve true n-key rollover without having a diode on every single button? How hard can it be?</p> <h3 id="mcetoc_1h03bofrk0">Watch the Video:</h3> <p><a href="https://www.youtube.com/watch?v=6R3AN3pvo-k">www.youtube.com/watch</a></p> <h3 id="mcetoc_1h03bsfpu3">Bonus Content:</h3> <ul> <li><a href="/challenges-projects/element14-presents/m/files/147593">Download all the Code for Free!</a></li> </ul> <h3 id="mcetoc_1h03bqutc1">Bill of Material:</h3> <table class="e14-product-bom-main"> <tbody> <tr> <th>Product Name</th> <th>Manufacturer</th> <th>Quantity</th> <th><a id="e14-product-link-6260f" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=3780506~9,2212779,2770338,2503749&nsku=29AK2184~9,45W6205,24AC5053,71Y9192&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_BUY_KIT" class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('6260f'));" data-farnell="3780506~9,2212779,2770338,2503749" data-newark="29AK2184~9,45W6205,24AC5053,71Y9192" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined~9,,," data-avnetema="undefined~9,,," data-avnetasia="undefined~9,,," >Buy Kit</a> </th> </tr> <tr> <td>LED, Super Red, Through Hole, T-1 3/4 (5mm), 12 mA, 5 V, 640 nm</td> <td>Multicomp</td> <td>9</td> <td><a id="e14-product-link-ba092" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=3780506&nsku=29AK2184&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('ba092'));" data-farnell="3780506" data-newark="29AK2184" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Arduino Mega 2560, ATmega2560, 54 I/O, 256KB Flash, 8KB SRAM, 4KB EEPROM</td> <td>Arduino</td> <td>1</td> <td><a id="e14-product-link-98dd6" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2212779&nsku=45W6205&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('98dd6'));" data-farnell="2212779" data-newark="45W6205" data-comoverride="" data-cmpoverride="" data-cpc="SC13721" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Jumper Wire Kit, Multicolour, 2 mm - 125 mm, 22 AWG, 140 Piece</td> <td>Multicomp</td> <td>1</td> <td><a id="e14-product-link-58e48" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2770338&nsku=24AC5053&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('58e48'));" data-farnell="2770338" data-newark="24AC5053" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Breadboard, Mounted, 1580 Pin, 10mm, x 135mm</td> <td>Multicomp</td> <td>1</td> <td><a id="e14-product-link-60d78" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2503749&nsku=71Y9192&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('60d78'));" data-farnell="2503749" data-newark="71Y9192" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr class="xs-hide"> <td>&nbsp;</td> <td></td> <td></td> <td></td> </tr> </tbody> </table> <p></p> <div style="background:#ffffff;border:1px solid #dadada;margin:0;padding:14px 16px 16px 18px;vertical-align:top;"> <div style="display:inline-block;float:left;padding:0px 25px 8px 0px;"><a href="/challengesprojects/element14-presents/"><img alt="element14 presents" src="/e14/assets/legacy/2018/e14PresentsJune818.png" width="180px" /></a></div> <div style="display:inline-block;vertical-align:top;width:70%;"></div> <div style="display:inline-block;vertical-align:top;width:70%;"><br /> <p style="margin:0;"><span><a class="jivecontainerTT-hover-container jive-link-community-small" href="/challengesprojects/element14-presents/">element14 presents</a></span>&nbsp; <strong>|</strong>&nbsp; <a class="jive-link-wiki-small" href="/challenges-projects/element14-presents/vcp-program/w/documents/3692/vcp-biography-clem">About Clem</a>&nbsp; <strong>|</strong>&nbsp; <a class="jivecontainerTT-hover-container jive-link-community-small" href="/challengesprojects/element14-presents/project-videos/">Project Videos</a></p> </div> </div><div style="clear:both;"></div> <div style="font-size: 90%;">Tags: buttons, keyboard, multiplexing, leds, Charlieplexing, arduino, friday_release, arduino mega, e14p_CMM</div> https://community.element14.com/challenges-projects/element14-presents/project-videos/w/documents/28140/charlieplexing-buttons-and-leds-at-the-same-time---how-hard-can-it-be----episode-604/revision/4Wed, 10 May 2023 17:48:46 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:a8a4d15d-6ca1-44b3-bb39-66e6b71b4b96tariq.ahmadhttps://community.element14.com/challenges-projects/element14-presents/project-videos/w/documents/28140/charlieplexing-buttons-and-leds-at-the-same-time---how-hard-can-it-be----episode-604#commentsRevision 4 posted to Documents by tariq.ahmad on 5/10/2023 5:48:46 PM<br /> <p>So many buttons so little IO. When you want to drive a large number of LEDs or read buttons the obvious choice is multiplexing them. But there is a method called charlieplexing that lets you use even more LEDs and buttons with even less IO pins. Clem wants to interface a large amount of buttons and LEDs with a microcontroller but has a limited number of pins.&nbsp; &nbsp;He&#39;s also trying to save money on parts. Could you just replace expensive signal diodes with cheap LEDs? Could you use the same pins to read buttons and drive LEDs in the same matrix? Could you also achieve true n-key rollover without having a diode on every single button? How hard can it be?</p> <h3 id="mcetoc_1h03bofrk0">Watch the Video:</h3> <p><a href="https://www.youtube.com/watch?v=6R3AN3pvo-k">www.youtube.com/watch</a></p> <h3 id="mcetoc_1h03bsfpu3">Bonus Content:</h3> <ul> <li><a href="/challenges-projects/element14-presents/secret-element14-presents/m/files/147593">Download all the Code for Free!</a></li> </ul> <h3 id="mcetoc_1h03bqutc1">Bill of Material:</h3> <table class="e14-product-bom-main"> <tbody> <tr> <th>Product Name</th> <th>Manufacturer</th> <th>Quantity</th> <th><a id="e14-product-link-c719e" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=3780506~9,2212779,2770338,2503749&nsku=29AK2184~9,45W6205,24AC5053,71Y9192&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_BUY_KIT" class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('c719e'));" data-farnell="3780506~9,2212779,2770338,2503749" data-newark="29AK2184~9,45W6205,24AC5053,71Y9192" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined~9,,," data-avnetema="undefined~9,,," data-avnetasia="undefined~9,,," >Buy Kit</a> </th> </tr> <tr> <td>LED, Super Red, Through Hole, T-1 3/4 (5mm), 12 mA, 5 V, 640 nm</td> <td>Multicomp</td> <td>9</td> <td><a id="e14-product-link-6369c" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=3780506&nsku=29AK2184&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('6369c'));" data-farnell="3780506" data-newark="29AK2184" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Arduino Mega 2560, ATmega2560, 54 I/O, 256KB Flash, 8KB SRAM, 4KB EEPROM</td> <td>Arduino</td> <td>1</td> <td><a id="e14-product-link-fc408" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2212779&nsku=45W6205&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('fc408'));" data-farnell="2212779" data-newark="45W6205" data-comoverride="" data-cmpoverride="" data-cpc="SC13721" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Jumper Wire Kit, Multicolour, 2 mm - 125 mm, 22 AWG, 140 Piece</td> <td>Multicomp</td> <td>1</td> <td><a id="e14-product-link-827ed" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2770338&nsku=24AC5053&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('827ed'));" data-farnell="2770338" data-newark="24AC5053" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Breadboard, Mounted, 1580 Pin, 10mm, x 135mm</td> <td>Multicomp</td> <td>1</td> <td><a id="e14-product-link-22b21" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2503749&nsku=71Y9192&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('22b21'));" data-farnell="2503749" data-newark="71Y9192" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr class="xs-hide"> <td>&nbsp;</td> <td></td> <td></td> <td></td> </tr> </tbody> </table> <p></p> <div style="background:#ffffff;border:1px solid #dadada;margin:0;padding:14px 16px 16px 18px;vertical-align:top;"> <div style="display:inline-block;float:left;padding:0px 25px 8px 0px;"><a href="/challengesprojects/element14-presents/"><img alt="element14 presents" src="/e14/assets/legacy/2018/e14PresentsJune818.png" width="180px" /></a></div> <div style="display:inline-block;vertical-align:top;width:70%;"></div> <div style="display:inline-block;vertical-align:top;width:70%;"><br /> <p style="margin:0;"><span><a class="jivecontainerTT-hover-container jive-link-community-small" href="/challengesprojects/element14-presents/">element14 presents</a></span>&nbsp; <strong>|</strong>&nbsp; <a class="jive-link-wiki-small" href="/challenges-projects/element14-presents/vcp-program/w/documents/3692/vcp-biography-clem">About Clem</a>&nbsp; <strong>|</strong>&nbsp; <a class="jivecontainerTT-hover-container jive-link-community-small" href="/challengesprojects/element14-presents/project-videos/">Project Videos</a></p> </div> </div><div style="clear:both;"></div> <div style="font-size: 90%;">Tags: buttons, keyboard, multiplexing, leds, Charlieplexing, arduino, friday_release, arduino mega, e14p_CMM</div> https://community.element14.com/challenges-projects/element14-presents/project-videos/w/documents/28140/charlieplexing-buttons-and-leds-at-the-same-time---how-hard-can-it-be----episode-604/revision/3Wed, 10 May 2023 17:48:22 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:a8a4d15d-6ca1-44b3-bb39-66e6b71b4b96tariq.ahmadhttps://community.element14.com/challenges-projects/element14-presents/project-videos/w/documents/28140/charlieplexing-buttons-and-leds-at-the-same-time---how-hard-can-it-be----episode-604#commentsRevision 3 posted to Documents by tariq.ahmad on 5/10/2023 5:48:22 PM<br /> <p>So many buttons so little IO. When you want to drive a large number of LEDs or read buttons the obvious choice is multiplexing them. But there is a method called charlieplexing that lets you use even more LEDs and buttons with even less IO pins. Clem wants to interface a large amount of buttons and LEDs with a microcontroller but has a limited number of pins.&nbsp; &nbsp;He&#39;s also trying to save money on parts. Could you just replace expensive signal diodes with cheap LEDs? Could you use the same pins to read buttons and drive LEDs in the same matrix? Could you also achieve true n-key rollover without having a diode on every single button? How hard could it be?</p> <h3 id="mcetoc_1h03bofrk0">Watch the Video:</h3> <p><a href="https://www.youtube.com/watch?v=6R3AN3pvo-k">www.youtube.com/watch</a></p> <h3 id="mcetoc_1h03bsfpu3">Bonus Content:</h3> <ul> <li><a href="/challenges-projects/element14-presents/secret-element14-presents/m/files/147593">Download all the Code for Free!</a></li> </ul> <h3 id="mcetoc_1h03bqutc1">Bill of Material:</h3> <table class="e14-product-bom-main"> <tbody> <tr> <th>Product Name</th> <th>Manufacturer</th> <th>Quantity</th> <th><a id="e14-product-link-7a371" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=3780506~9,2212779,2770338,2503749&nsku=29AK2184~9,45W6205,24AC5053,71Y9192&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_BUY_KIT" class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('7a371'));" data-farnell="3780506~9,2212779,2770338,2503749" data-newark="29AK2184~9,45W6205,24AC5053,71Y9192" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined~9,,," data-avnetema="undefined~9,,," data-avnetasia="undefined~9,,," >Buy Kit</a> </th> </tr> <tr> <td>LED, Super Red, Through Hole, T-1 3/4 (5mm), 12 mA, 5 V, 640 nm</td> <td>Multicomp</td> <td>9</td> <td><a id="e14-product-link-5e5d2" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=3780506&nsku=29AK2184&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('5e5d2'));" data-farnell="3780506" data-newark="29AK2184" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Arduino Mega 2560, ATmega2560, 54 I/O, 256KB Flash, 8KB SRAM, 4KB EEPROM</td> <td>Arduino</td> <td>1</td> <td><a id="e14-product-link-0aea1" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2212779&nsku=45W6205&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('0aea1'));" data-farnell="2212779" data-newark="45W6205" data-comoverride="" data-cmpoverride="" data-cpc="SC13721" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Jumper Wire Kit, Multicolour, 2 mm - 125 mm, 22 AWG, 140 Piece</td> <td>Multicomp</td> <td>1</td> <td><a id="e14-product-link-494a4" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2770338&nsku=24AC5053&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('494a4'));" data-farnell="2770338" data-newark="24AC5053" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Breadboard, Mounted, 1580 Pin, 10mm, x 135mm</td> <td>Multicomp</td> <td>1</td> <td><a id="e14-product-link-65536" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2503749&nsku=71Y9192&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('65536'));" data-farnell="2503749" data-newark="71Y9192" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr class="xs-hide"> <td>&nbsp;</td> <td></td> <td></td> <td></td> </tr> </tbody> </table> <p></p> <div style="background:#ffffff;border:1px solid #dadada;margin:0;padding:14px 16px 16px 18px;vertical-align:top;"> <div style="display:inline-block;float:left;padding:0px 25px 8px 0px;"><a href="/challengesprojects/element14-presents/"><img alt="element14 presents" src="/e14/assets/legacy/2018/e14PresentsJune818.png" width="180px" /></a></div> <div style="display:inline-block;vertical-align:top;width:70%;"></div> <div style="display:inline-block;vertical-align:top;width:70%;"><br /> <p style="margin:0;"><span><a class="jivecontainerTT-hover-container jive-link-community-small" href="/challengesprojects/element14-presents/">element14 presents</a></span>&nbsp; <strong>|</strong>&nbsp; <a class="jive-link-wiki-small" href="/challenges-projects/element14-presents/vcp-program/w/documents/3692/vcp-biography-clem">About Clem</a>&nbsp; <strong>|</strong>&nbsp; <a class="jivecontainerTT-hover-container jive-link-community-small" href="/challengesprojects/element14-presents/project-videos/">Project Videos</a></p> </div> </div><div style="clear:both;"></div> <div style="font-size: 90%;">Tags: buttons, keyboard, multiplexing, leds, Charlieplexing, arduino, friday_release, arduino mega, e14p_CMM</div> https://community.element14.com/challenges-projects/element14-presents/project-videos/w/documents/28140/charlieplexing-buttons-and-leds-at-the-same-time---how-hard-can-it-be----episode-604/revision/2Wed, 10 May 2023 17:47:10 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:a8a4d15d-6ca1-44b3-bb39-66e6b71b4b96tariq.ahmadhttps://community.element14.com/challenges-projects/element14-presents/project-videos/w/documents/28140/charlieplexing-buttons-and-leds-at-the-same-time---how-hard-can-it-be----episode-604#commentsRevision 2 posted to Documents by tariq.ahmad on 5/10/2023 5:47:10 PM<br /> <p>So many buttons so little IO. When you want to drive a large number of LEDs or read buttons the obvious choice is multiplexing them. But there is a method called charlieplexing that lets you use even more LEDs and buttons with even less IO pins. Clem wants to interface a large amount of buttons and LEDs with a microcontroller but has a limited number of pins.&nbsp; &nbsp;He&#39;s also trying to save money on parts. Could you just replace expensive signal diodes with cheap LEDs? Could you use the same pins to read buttons and drive LEDs in the same matrix? Could you also achieve true n-key rollover without having a diode on every single button? How hard could it be?</p> <h3 id="mcetoc_1h03bofrk0">Watch the Video:</h3> <p><a href="https://www.youtube.com/watch?v=6R3AN3pvo-k">www.youtube.com/watch</a></p> <h3 id="mcetoc_1h03bsfpu3">Bonus Content:</h3> <ul> <li><a href="/challenges-projects/element14-presents/secret-element14-presents/m/files/147593">Download all the Code for Free!</a></li> </ul> <h3 id="mcetoc_1h03bqutc1">Bill of Material:</h3> <table class="e14-product-bom-main"> <tbody> <tr> <th>Product Name</th> <th>Manufacturer</th> <th>Quantity</th> <th><a id="e14-product-link-18a4e" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=3780506~9,2212779,2770338,2503749&nsku=29AK2184~9,45W6205,24AC5053,71Y9192&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_BUY_KIT" class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('18a4e'));" data-farnell="3780506~9,2212779,2770338,2503749" data-newark="29AK2184~9,45W6205,24AC5053,71Y9192" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined~9,,," data-avnetema="undefined~9,,," data-avnetasia="undefined~9,,," >Buy Kit</a> </th> </tr> <tr> <td>LED, Super Red, Through Hole, T-1 3/4 (5mm), 12 mA, 5 V, 640 nm</td> <td>Multicomp</td> <td>9</td> <td><a id="e14-product-link-4f2d7" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=3780506&nsku=29AK2184&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('4f2d7'));" data-farnell="3780506" data-newark="29AK2184" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Arduino Mega 2560, ATmega2560, 54 I/O, 256KB Flash, 8KB SRAM, 4KB EEPROM</td> <td>Arduino</td> <td>1</td> <td><a id="e14-product-link-fc437" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2212779&nsku=45W6205&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('fc437'));" data-farnell="2212779" data-newark="45W6205" data-comoverride="" data-cmpoverride="" data-cpc="SC13721" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Jumper Wire Kit, Multicolour, 2 mm - 125 mm, 22 AWG, 140 Piece</td> <td>Multicomp</td> <td>1</td> <td><a id="e14-product-link-96c2c" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2770338&nsku=24AC5053&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('96c2c'));" data-farnell="2770338" data-newark="24AC5053" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Breadboard, Mounted, 1580 Pin, 10mm, x 135mm</td> <td>Multicomp</td> <td>1</td> <td><a id="e14-product-link-58081" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2503749&nsku=71Y9192&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('58081'));" data-farnell="2503749" data-newark="71Y9192" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr class="xs-hide"> <td>&nbsp;</td> <td></td> <td></td> <td></td> </tr> </tbody> </table> <p></p> <div style="background:#ffffff;border:1px solid #dadada;margin:0;padding:14px 16px 16px 18px;vertical-align:top;"> <div style="display:inline-block;float:left;padding:0px 25px 8px 0px;"><a href="/challengesprojects/element14-presents/"><img alt="element14 presents" src="/e14/assets/legacy/2018/e14PresentsJune818.png" width="180px" /></a></div> <div style="display:inline-block;vertical-align:top;width:70%;"></div> <div style="display:inline-block;vertical-align:top;width:70%;"><br /> <p style="margin:0;"><span><a class="jivecontainerTT-hover-container jive-link-community-small" href="/challengesprojects/element14-presents/">element14 presents</a></span>&nbsp; <strong>|</strong>&nbsp; <a class="jive-link-wiki-small" href="/challenges-projects/element14-presents/vcp-program/w/documents/3692/vcp-biography-clem">About Clem</a>&nbsp; <strong>|</strong>&nbsp; <a class="jivecontainerTT-hover-container jive-link-community-small" href="/challengesprojects/element14-presents/project-videos/">Project Videos</a></p> </div> </div><div style="clear:both;"></div> <div style="font-size: 90%;">Tags: buttons, keyboard, multiplexing, leds, Charlieplexing, arduino, friday_release, arduino mega, e14p_CMM</div> https://community.element14.com/challenges-projects/element14-presents/project-videos/w/documents/28140/charlieplexing-buttons-and-leds-at-the-same-time---how-hard-can-it-be----episode-604/revision/1Wed, 10 May 2023 17:43:26 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:a8a4d15d-6ca1-44b3-bb39-66e6b71b4b96tariq.ahmadhttps://community.element14.com/challenges-projects/element14-presents/project-videos/w/documents/28140/charlieplexing-buttons-and-leds-at-the-same-time---how-hard-can-it-be----episode-604#commentsRevision 1 posted to Documents by tariq.ahmad on 5/10/2023 5:43:26 PM<br /> <p>So many buttons so little IO. When you want to drive a large number of LEDs or read buttons the obvious choice is multiplexing them. But there is a method called charlieplexing that lets you use even more LEDs and buttons with even less IO pins. Clem wants to interface a large amount of buttons and LEDs with a microcontroller but has a limited number of pins.&nbsp; &nbsp;He&#39;s also trying to save money on parts. Could you just replace expensive signal diodes with cheap LEDs? Could you use the same pins to read buttons and drive LEDs in the same matrix? Could you also achieve true n-key rollover without having a diode on every single button? How hard could it be?</p> <h3 id="mcetoc_1h03bofrk0">Watch the Video:</h3> <p><a href="https://www.youtube.com/watch?v=6R3AN3pvo-k">www.youtube.com/watch</a></p> <h3 id="mcetoc_1h03bsfpu3">Bonus Content:</h3> <ul> <li>Download all the Code for Free!</li> </ul> <h3 id="mcetoc_1h03bqutc1">Bill of Material:</h3> <table class="e14-product-bom-main"> <tbody> <tr> <th>Product Name</th> <th>Manufacturer</th> <th>Quantity</th> <th><a id="e14-product-link-28791" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=3780506~9,2212779,2770338,2503749&nsku=29AK2184~9,45W6205,24AC5053,71Y9192&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_BUY_KIT" class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('28791'));" data-farnell="3780506~9,2212779,2770338,2503749" data-newark="29AK2184~9,45W6205,24AC5053,71Y9192" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined~9,,," data-avnetema="undefined~9,,," data-avnetasia="undefined~9,,," >Buy Kit</a> </th> </tr> <tr> <td>LED, Super Red, Through Hole, T-1 3/4 (5mm), 12 mA, 5 V, 640 nm</td> <td>Multicomp</td> <td>9</td> <td><a id="e14-product-link-ad85a" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=3780506&nsku=29AK2184&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('ad85a'));" data-farnell="3780506" data-newark="29AK2184" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Arduino Mega 2560, ATmega2560, 54 I/O, 256KB Flash, 8KB SRAM, 4KB EEPROM</td> <td>Arduino</td> <td>1</td> <td><a id="e14-product-link-878d1" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2212779&nsku=45W6205&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('878d1'));" data-farnell="2212779" data-newark="45W6205" data-comoverride="" data-cmpoverride="" data-cpc="SC13721" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Jumper Wire Kit, Multicolour, 2 mm - 125 mm, 22 AWG, 140 Piece</td> <td>Multicomp</td> <td>1</td> <td><a id="e14-product-link-75416" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2770338&nsku=24AC5053&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('75416'));" data-farnell="2770338" data-newark="24AC5053" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr> <td>Breadboard, Mounted, 1580 Pin, 10mm, x 135mm</td> <td>Multicomp</td> <td>1</td> <td><a id="e14-product-link-0f13c" data-at-areainteracted="rte-content" data-at-type="click" data-at-link-type="button" href="https://referral.element14.com/OrderCodeView?fsku=2503749&nsku=71Y9192&COM=e14c-noscript&CMP=e14c-noscript&osetc=e14-noscript-tracking-loss" data-at-label="PRODUCT_POPUP_OPEN"class="e14-embedded e14_shopping-cart-far e14-button" onclick="event.preventDefault();e14.func.displayProduct(e14.meta.user.country, this, 'embedded-link', e14.func.getProductLinkJSON('0f13c'));" data-farnell="2503749" data-newark="71Y9192" data-comoverride="" data-cmpoverride="" data-cpc="" data-avnetemea="undefined" data-avnetema="undefined" data-avnetasia="undefined" >Buy Now</a> </td> </tr> <tr class="xs-hide"> <td>&nbsp;</td> <td></td> <td></td> <td></td> </tr> </tbody> </table> <p></p> <div style="background:#ffffff;border:1px solid #dadada;margin:0;padding:14px 16px 16px 18px;vertical-align:top;"> <div style="display:inline-block;float:left;padding:0px 25px 8px 0px;"><a href="/challengesprojects/element14-presents/"><img alt="element14 presents" src="/e14/assets/legacy/2018/e14PresentsJune818.png" width="180px" /></a></div> <div style="display:inline-block;vertical-align:top;width:70%;"></div> <div style="display:inline-block;vertical-align:top;width:70%;"><br /> <p style="margin:0;"><span><a class="jivecontainerTT-hover-container jive-link-community-small" href="/challengesprojects/element14-presents/">element14 presents</a></span>&nbsp; <strong>|</strong>&nbsp; <a class="jive-link-wiki-small" href="/challenges-projects/element14-presents/vcp-program/w/documents/3692/vcp-biography-clem">About Clem</a>&nbsp; <strong>|</strong>&nbsp; <a class="jivecontainerTT-hover-container jive-link-community-small" href="/challengesprojects/element14-presents/project-videos/">Project Videos</a></p> </div> </div><div style="clear:both;"></div> <div style="font-size: 90%;">Tags: buttons, keyboard, multiplexing, leds, Charlieplexing, arduino, friday_release, arduino mega, e14p_CMM</div>