{"id":200,"date":"2019-03-31T20:40:42","date_gmt":"2019-03-31T20:40:42","guid":{"rendered":"https:\/\/dial-a-grue.com\/gory\/?p=200"},"modified":"2019-03-31T20:40:42","modified_gmt":"2019-03-31T20:40:42","slug":"getting-the-keypad-working","status":"publish","type":"post","link":"https:\/\/dial-a-grue.com\/gory\/?p=200","title":{"rendered":"Getting the keypad working."},"content":{"rendered":"\n

So, if I’m going to have 3 working phones for the Maker faire, I better get to building them. Today’s project is to get the keypad working. Oringally this keypad used a touch-tone signaling mechanism, <\/a>but that wasn’t necessary for my purposes, so I just cut out all the DTMF hardware to get at the switches that the buttons operate. There are 12 buttons (3 columns and 4 rows) of numbers and symbols. The way these keypads operate is that each row and column has it’s own switch, and each button closes the switch for that column and that row. I wired each of those switches up to an I\/O line on the raspberry pi 3B that I’m using as the brains of the Gruebox 1.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

In the original phone, each column and row had its own tone, and so each number\/symbol played two tones, hence Dual Tone Multi-Frequency. I just built a lookup table of switch values that map to symbols\/numbers, and that’s how I decode which button is pressed.<\/p>\n\n\n\n

Here’s a test run of the decoding:<\/p>\n\n\n\n

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Testing Gruebox1 keypad<\/figcaption><\/figure>\n\n\n\n

So all 12 buttons work. There is also a switch for the on\/off hook that isn’t connected yet, so I’m just wired of off-hook for now, so I can test.<\/p>\n\n\n\n

I also removed the fake wood-grain sticker on the faceplate. It’s still got some residue from the adhesive, but I’ll take care of that later. Assembled it looks like:<\/p>\n\n\n\n

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Gruebox 1 keypad assembled and ready to put into the case.<\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"

So, if I’m going to have 3 working phones for the Maker faire, I better get to building them. Today’s project is to get the keypad working. Oringally this keypad used a touch-tone signaling mechanism, but that wasn’t necessary for my purposes, so I just cut out all the DTMF hardware to get at the […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3,7,8],"tags":[],"class_list":["post-200","post","type-post","status-publish","format-standard","hentry","category-brains","category-phone","category-wetwork"],"_links":{"self":[{"href":"https:\/\/dial-a-grue.com\/gory\/index.php?rest_route=\/wp\/v2\/posts\/200","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/dial-a-grue.com\/gory\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/dial-a-grue.com\/gory\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/dial-a-grue.com\/gory\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/dial-a-grue.com\/gory\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=200"}],"version-history":[{"count":0,"href":"https:\/\/dial-a-grue.com\/gory\/index.php?rest_route=\/wp\/v2\/posts\/200\/revisions"}],"wp:attachment":[{"href":"https:\/\/dial-a-grue.com\/gory\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=200"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dial-a-grue.com\/gory\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=200"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dial-a-grue.com\/gory\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=200"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}