{"id":5369,"date":"2025-12-31T19:30:40","date_gmt":"2026-01-01T00:30:40","guid":{"rendered":"https:\/\/www.paleotechnologist.net\/?p=5369"},"modified":"2025-12-31T19:30:41","modified_gmt":"2026-01-01T00:30:41","slug":"serial-led-matrix","status":"publish","type":"post","link":"https:\/\/www.paleotechnologist.net\/?p=5369","title":{"rendered":"Serial LED Matrix"},"content":{"rendered":"\n

Specialty chips like the MAX7219 <\/a>can make visually-striking devices easier to work with. The ‘7219 is designed to drive an 8×8 matrix of LEDs, from a single SPI input. Additional modules can be easily added to the chain, allowing the creation of larger displays. A few helper C functions fold the pixels into the usual rectangular shape even if they’re not wired that way. With the SPI interface, updates are fast — at least several dozen Hz for four modules (32×8).<\/p>\n\n\n\n

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Four blue 8×8 LED modules.
(They’re blue, not pale-blue or white — but even the lowest brightness overpowers the camera.)<\/figcaption><\/figure>\n\n\n\n
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Each module sends excess data on to the next one.
The only limit (other than supply current, which could be supplied) is update time.<\/figcaption><\/figure>\n\n\n\n

Weirdly, even though the modules are sold as (and work as) MAX7219 chips, the ICs themselves seem to have had any identifying markings removed. (The original seller photos show both Maxim<\/a>-branded (now part of Analog Devices) as well as the anonymous chips.)<\/p>\n\n\n\n

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The product listing says it’s a MAX7219. It works like one. Why the obfuscation?<\/figcaption><\/figure>\n\n\n\n

A basic Arduino sketch (tested on ESP32) is up on GitHub. I’ll probably add digits next, if there isn’t a library already out there, suitable for these. They’d make a good compass display for the Santana.<\/p>\n\n\n\n

Just don’t try to take a picture of them without strong lighting…<\/p>\n\n\n\n

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This isn’t how it looks IRL either, but it gives you an idea of the level of blue. At low brightness.<\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"

Daisy-chained SPI interfaces and fast microcontrollers make driving large, bright LED displays easy. Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_exactmetrics_skip_tracking":false,"footnotes":""},"categories":[249,265,238,225,475],"tags":[498,497],"class_list":["post-5369","post","type-post","status-publish","format-standard","hentry","category-c","category-components-electronics","category-electronics","category-toys","category-user-interface-design","tag-arduino","tag-c"],"_links":{"self":[{"href":"https:\/\/www.paleotechnologist.net\/index.php?rest_route=\/wp\/v2\/posts\/5369","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.paleotechnologist.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.paleotechnologist.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.paleotechnologist.net\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.paleotechnologist.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=5369"}],"version-history":[{"count":1,"href":"https:\/\/www.paleotechnologist.net\/index.php?rest_route=\/wp\/v2\/posts\/5369\/revisions"}],"predecessor-version":[{"id":5375,"href":"https:\/\/www.paleotechnologist.net\/index.php?rest_route=\/wp\/v2\/posts\/5369\/revisions\/5375"}],"wp:attachment":[{"href":"https:\/\/www.paleotechnologist.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=5369"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.paleotechnologist.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=5369"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.paleotechnologist.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=5369"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}