{"id":2845,"date":"2019-01-06T23:03:13","date_gmt":"2019-01-06T21:03:13","guid":{"rendered":"http:\/\/tinusaur.org\/?p=2845"},"modified":"2022-01-17T22:11:34","modified_gmt":"2022-01-17T20:11:34","slug":"interfacing-a-max7219-driven-led-matrix-with-attiny85","status":"publish","type":"post","link":"https:\/\/tinusaur.org\/2019\/01\/06\/interfacing-a-max7219-driven-led-matrix-with-attiny85\/","title":{"rendered":"Interfacing a MAX7219 Driven LED Matrix with ATtiny85"},"content":{"rendered":"\n<p class=\"has-black-color has-text-color has-background\" style=\"background-color:#eeeeee\"><strong>UPDATE <\/strong>2022: The <strong>MAX7219LED8x8<\/strong> library, now renamed to <a href=\"https:\/\/tinusaur.com\/libraries\/max7219tiny\/\"><strong>MAX7219tiny<\/strong><\/a> has now a new home at <a href=\"https:\/\/tinusaur.com\/libraries\/max7219tiny\/\">tinusaur.com\/libraries\/max7219tiny<\/a>. Check also this&nbsp;<a href=\"https:\/\/tinusaur.com\/tutorials\/max7219-attiny85-interface\/\"><strong>MAX7219<\/strong> &amp; <strong>ATtiny85<\/strong> tutorial<\/a>&nbsp;to learn how the library works.<\/p>\n\n\n\n<p>The\u00a0<a rel=\"noreferrer noopener\" href=\"http:\/\/www.maximintegrated.com\/en\/products\/power\/display-power-control\/MAX7219.html\" target=\"_blank\">MAX7219<\/a>\u00a0controller manufactured by\u00a0Maxim Integrated\u00a0is\u00a0a compact, serial input\/output common-cathode display driver that could interface microcontrollers to 64 individual LEDs, 7-segment numeric LED displays of up to 8 digits, bar-graph displays, etc. Included on-chip are a BCD code-B decoder, multiplex scan circuitry, segment and digit drivers, and an 8\u00d78 <a href=\"https:\/\/en.wikipedia.org\/wiki\/Static_random-access_memory\">static RAM<\/a> that stores each digit.\u00a0 <\/p>\n\n\n\n<p>The <strong>MAX7219<\/strong> modules are very convenient to use with microcontrollers such as <a href=\"https:\/\/www.microchip.com\/wwwproducts\/en\/ATtiny85\">ATtiny85<\/a>, or, in our case the <a href=\"\/products\/boards\/\">Tinusaur Board<\/a>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">The Hardware<\/h2>\n\n\n\n<p>The MAX7219 modules usually look like this:<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"1280\" height=\"720\" src=\"https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_ledmatrix8x8_assembling_010_cs1280x720fx1.jpg\" alt=\"MAX7219 Module LED Matrix 8x8\" class=\"wp-image-2848\" srcset=\"https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_ledmatrix8x8_assembling_010_cs1280x720fx1.jpg 1280w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_ledmatrix8x8_assembling_010_cs1280x720fx1-300x169.jpg 300w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_ledmatrix8x8_assembling_010_cs1280x720fx1-1024x576.jpg 1024w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_ledmatrix8x8_assembling_010_cs1280x720fx1-768x432.jpg 768w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_ledmatrix8x8_assembling_010_cs1280x720fx1-772x434.jpg 772w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_ledmatrix8x8_assembling_010_cs1280x720fx1-1230x692.jpg 1230w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_ledmatrix8x8_assembling_010_cs1280x720fx1-314x177.jpg 314w\" sizes=\"(max-width: 1280px) 100vw, 1280px\" \/><figcaption>MAX7219 Module and LED Matrix 8&#215;8<\/figcaption><\/figure>\n\n\n\n<p>They have an input bus on one side and output bus on the other. This allows you to <a href=\"https:\/\/en.wikipedia.org\/wiki\/Daisy_chain_(electrical_engineering)\">daisy chain<\/a> 2 or more modules, i.e. one after another, to create more complicated setups.<\/p>\n\n\n\n<p>The modules that we are using are capable of connecting in a chain using 5 small jumpers. See the picture below.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"1280\" height=\"720\" src=\"https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_ledmatrix8x8_assembling_104_cs1280x720fx1.jpg\" alt=\"MAX7219 Module LED Matrix 8x8\" class=\"wp-image-2850\" srcset=\"https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_ledmatrix8x8_assembling_104_cs1280x720fx1.jpg 1280w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_ledmatrix8x8_assembling_104_cs1280x720fx1-300x169.jpg 300w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_ledmatrix8x8_assembling_104_cs1280x720fx1-1024x576.jpg 1024w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_ledmatrix8x8_assembling_104_cs1280x720fx1-768x432.jpg 768w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_ledmatrix8x8_assembling_104_cs1280x720fx1-772x434.jpg 772w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_ledmatrix8x8_assembling_104_cs1280x720fx1-1230x692.jpg 1230w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_ledmatrix8x8_assembling_104_cs1280x720fx1-314x177.jpg 314w\" sizes=\"(max-width: 1280px) 100vw, 1280px\" \/><figcaption>2x MAX7219 Modules Connected<\/figcaption><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">Pinout and Signals<\/h2>\n\n\n\n<p>MAX7219 module has 5 pins:<\/p>\n\n\n\n<ul><li>VCC &#8211; power (+)<\/li><li>GND &#8211; ground (-)<\/li><li>DIN &#8211; Data input<\/li><li>CS &#8211; Chip select<\/li><li>CLK &#8211; Clock<\/li><\/ul>\n\n\n\n<p>That means that we need 3 pins on the ATtiny85 microcontroller side to control the module. Those will be:<\/p>\n\n\n\n<ul><li>PB0 &#8211; connected to the CLK<\/li><li>PB1 &#8211; connected to the CS<\/li><li>PB2 &#8211; connected to the DIN<\/li><\/ul>\n\n\n\n<p>This is sufficient to connect to the MAX7219 module and program it.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">The Protocol<\/h2>\n\n\n\n<p>Communicating with the MAX7219 is relatively easy &#8211; it uses a <a href=\"https:\/\/en.wikipedia.org\/wiki\/Synchronous_Serial_Interface\">synchronous protocol<\/a> which means that for every data bit we send there is a clock cycle that signifies the presence of that data bit.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"600\" height=\"340\" src=\"https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2014\/07\/max7219_timing_diagram_sc600x340.png\" alt=\"MAX7219 Timing Diagram\" class=\"wp-image-724\" srcset=\"https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2014\/07\/max7219_timing_diagram_sc600x340.png 600w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2014\/07\/max7219_timing_diagram_sc600x340-300x170.png 300w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2014\/07\/max7219_timing_diagram_sc600x340-314x178.png 314w\" sizes=\"(max-width: 600px) 100vw, 600px\" \/><figcaption>MAX7219 Timing Diagram<\/figcaption><\/figure>\n\n\n\n<p>In other words, we send 2 parallel sequences to bits &#8211; one for the clock and another for the data. This is what the software does.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">The Software<\/h2>\n\n\n\n<p>The way this MAX7219 module works is this:<\/p>\n\n\n\n<ul><li>We write bytes to its internal register.<\/li><li>MAX7219 interprets the data.<\/li><li>MAX7219 controls the LEDs in the matrix.<\/li><\/ul>\n\n\n\n<p>That also means that we don&#8217;t have to circle through the array of LEDs all the time in order to light them up &#8211; the MAX7219 controller takes care of that. It could also manage the intensity of the LEDs.<\/p>\n\n\n\n<p>So, to use the MAX7219 modules in a convenient way we need a library of functions to serve that purpose.<\/p>\n\n\n\n<p>First, we need some basic functions in order to write to the  MAX7219&nbsp;registers.<\/p>\n\n\n\n<ul><li>Writing a byte to the MAX7219.<\/li><li>Writing a word (2 bytes) to the MAX7219.<\/li><\/ul>\n\n\n\n<p>The function that writes one byte to the controller looks like this:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>void max7219_byte(uint8_t data) {\n    for(uint8_t i = 8; i &gt;= 1; i--) {\n        PORTB &amp;= ~(1 &lt;&lt; MAX7219_CLK);   \/\/ Set CLK to LOW\n        if (data &amp; 0x80)                \/\/ Mask the MSB of the data\n            PORTB |= (1 &lt;&lt; MAX7219_DIN);    \/\/ Set DIN to HIGH\n        else\n            PORTB &amp;= ~(1 &lt;&lt; MAX7219_DIN);   \/\/ Set DIN to LOW\n        PORTB |= (1 &lt;&lt; MAX7219_CLK);        \/\/ Set CLK to HIGH\n        data &lt;&lt;= 1;                     \/\/ Shift to the left\n    }\n}<\/code><\/pre>\n\n\n\n<p>Now that we can send bytes to the MAX7219 we can start sending commands. This is done by sending 2 byes &#8211; 1st for the address of the internal register and the 2nd for the data we&#8217;d like to send.<\/p>\n\n\n\n<p>There is more than a dozen of register in the MAX7219 controller.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"600\" height=\"720\" src=\"https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2014\/07\/max7219_commands_cs600x720fx.png\" alt=\"MAX7219 Registers and Commands\" class=\"wp-image-726\" srcset=\"https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2014\/07\/max7219_commands_cs600x720fx.png 600w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2014\/07\/max7219_commands_cs600x720fx-250x300.png 250w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2014\/07\/max7219_commands_cs600x720fx-160x192.png 160w\" sizes=\"(max-width: 600px) 100vw, 600px\" \/><figcaption>MAX7219 Registers and Commands<\/figcaption><\/figure>\n\n\n\n<p>Sending a command, or a word, is basically sending 2 consecutive bytes. The function implementing that is very simple.<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>void max7219_word(uint8_t address, uint8_t data) {\n    PORTB &amp;= ~(1 &lt;&lt; MAX7219_CS);    \/\/ Set CS to LOW\n    max7219_byte(address);          \/\/ Sending the address\n    max7219_byte(data);             \/\/ Sending the data\n    PORTB |= (1 &lt;&lt; MAX7219_CS);     \/\/ Set CS to HIGH\n    PORTB &amp;= ~(1 &lt;&lt; MAX7219_CLK);   \/\/ Set CLK to LOW\n}<\/code><\/pre>\n\n\n\n<p>It is important to note here the line where we bring the CS signal back to HIGH &#8211; this marks the end of the sequence &#8211; in this case, the end of the command. A similar technique is used when controlling more than one matrix connected in a chain.<\/p>\n\n\n\n<p>Next step, before we start turning on and off the LEDs, is to initialize the MAX7219 controller. This is done by writing certain values to certain registers. For convenience, while coding it we could put the initialization sequence in an array.<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>uint8_t initseq&#91;] = {\n    0x09, 0x00, \/\/ Decode-Mode Register, 00 = No decode\n    0x0a, 0x01, \/\/ Intensity Register, 0x00 .. 0x0f\n    0x0b, 0x07, \/\/ Scan-Limit Register, 0x07 to show all lines\n    0x0c, 0x01, \/\/ Shutdown Register, 0x01 = Normal Operation\n    0x0f, 0x00, \/\/ Display-Test Register, 0x00 = Normal Operation\n};<\/code><\/pre>\n\n\n\n<p>We just need to send the 5 commands above in a sequence as address\/data pairs.<\/p>\n\n\n\n<p>Next step &#8211; lighting up a row of LEDs.<\/p>\n\n\n\n<p>This is very simple &#8211; we just write one command where 1st byte is the address (from 1 to 8) and the 2nd byte is the 8 bits representing the 8 LEDs in the row.<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>void max7219_row(uint8_t address, uint8_t data) {\n    if (address &gt;= 1 &amp;&amp; address &lt;= 8) max7219_word(address, data);\n}<\/code><\/pre>\n\n\n\n<p>It is important to note that this will work for 1 matrix only. If we connect more matrices in a chain they will all show the same data. The reason for this is that after sending the command we bring the CS signal back to HIGH which causes all the MAX7219 controllers in the chain to latch and show whatever the last command was.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Testing<\/h2>\n\n\n\n<p>This is a simple testing program that lights up a LED on the first row (r=1) on the right-most position, then moves that on the left until it reaches the left-most position, then does the same on one row up (r=2) )until it reaches the top (r=8).<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>max7219_init();\nfor (;;) {\n    for (uint8_t r = 1; r &lt;= 8; r++) {\n        uint8_t d = 1;\n        for (uint8_t i = 9; i &gt; 0; i--) {\n            max7219_row(r, d);\n            d = d &lt;&lt; 1;\n            _delay_ms(50);\n        }\n    }\n}<\/code><\/pre>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"640\" height=\"480\" src=\"https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20190106_max7219led8x8_test_11_fx1o.gif\" alt=\"MAX7219 Testing MAX7219LED8x8 Library\" class=\"wp-image-2873\"\/><figcaption>MAX7219 Testing<\/figcaption><\/figure><\/div>\n\n\n\n<p>This testing code doesn&#8217;t do much but it demonstrates how to communicate with the MAX7219 controller.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">The MAX7219LED8x8 Library<\/h2>\n\n\n\n<p>All of the functions mentioned above are part of the <a href=\"\/software\/libraries\/max7219led8x8\/\">MAX7219LED8x8 library<\/a>. Its source code is available at <a rel=\"noreferrer noopener\" href=\"https:\/\/bitbucket.org\/tinusaur\/max7219led8x8\" target=\"_blank\">https:\/\/bitbucket.org\/tinusaur\/max7219led8x8<\/a>. <\/p>\n\n\n\n<h2 class=\"wp-block-heading\">The Tinusaur Shield GAMEx3<\/h2>\n\n\n\n<p>If you already have a <a href=\"\/products\/boards\/\">Tinusaur Board<\/a> we have the <a href=\"\/products\/shields\/tinusaur-shield-gamex3\/\">Shield GAMEx3<\/a> for it to connect a MAX7219 module easier to your ATtiny85 microcontroller.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><a href=\"\/products\/shields\/tinusaur-shield-gamex3\/\"><img loading=\"lazy\" decoding=\"async\" width=\"1280\" height=\"720\" src=\"https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_shieldgamex3_assembling_190_rcs1280x720fx1.jpg\" alt=\"Shield GAMEx3\" class=\"wp-image-2895\" srcset=\"https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_shieldgamex3_assembling_190_rcs1280x720fx1.jpg 1280w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_shieldgamex3_assembling_190_rcs1280x720fx1-300x169.jpg 300w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_shieldgamex3_assembling_190_rcs1280x720fx1-1024x576.jpg 1024w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_shieldgamex3_assembling_190_rcs1280x720fx1-768x432.jpg 768w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_shieldgamex3_assembling_190_rcs1280x720fx1-772x434.jpg 772w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_shieldgamex3_assembling_190_rcs1280x720fx1-1230x692.jpg 1230w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181216_shieldgamex3_assembling_190_rcs1280x720fx1-314x177.jpg 314w\" sizes=\"(max-width: 1280px) 100vw, 1280px\" \/><\/a><figcaption>Shield GAMEx3<\/figcaption><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">The Gametinu Project<\/h2>\n\n\n\n<p>The <a href=\"\/projects\/gametinu\/\">Gametinu<\/a> is a small game platform that you could build yourself using the <a href=\"\/products\/shields\/shield-gamex3\/\">Shield GAMEx3<\/a> and a few more parts and tools.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><a href=\"\/projects\/gametinu\/\"><img loading=\"lazy\" decoding=\"async\" width=\"1280\" height=\"720\" src=\"https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181224_gametinu_assembling_108_cs1280x720fx2.jpg\" alt=\"Gametinu\" class=\"wp-image-2901\" srcset=\"https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181224_gametinu_assembling_108_cs1280x720fx2.jpg 1280w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181224_gametinu_assembling_108_cs1280x720fx2-300x169.jpg 300w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181224_gametinu_assembling_108_cs1280x720fx2-1024x576.jpg 1024w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181224_gametinu_assembling_108_cs1280x720fx2-768x432.jpg 768w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181224_gametinu_assembling_108_cs1280x720fx2-772x434.jpg 772w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181224_gametinu_assembling_108_cs1280x720fx2-1230x692.jpg 1230w, https:\/\/tinusaur.org\/wp-content\/uploads\/sites\/9\/2019\/01\/20181224_gametinu_assembling_108_cs1280x720fx2-314x177.jpg 314w\" sizes=\"(max-width: 1280px) 100vw, 1280px\" \/><\/a><figcaption>Gametinu<\/figcaption><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">References<\/h2>\n\n\n\n<p>MAX7219 specification and datasheet:<\/p>\n\n\n\n<ul><li><a rel=\"noreferrer noopener\" href=\"http:\/\/www.maximintegrated.com\/en\/products\/power\/display-power-control\/MAX7219.html\" target=\"_blank\">http:\/\/www.maximintegrated.com\/&#8230;\/MAX7219.html<\/a><\/li><li><a rel=\"noreferrer noopener\" href=\"http:\/\/datasheets.maximintegrated.com\/en\/ds\/MAX7219-MAX7221.pdf\" target=\"_blank\">http:\/\/datasheets.maximintegrated.com\/en\/ds\/MAX7219-MAX7221.pdf<\/a><\/li><\/ul>\n\n\n\n<hr class=\"wp-block-separator\"\/>\n\n\n\n<p>This article is a rewritten version of another article from 2014:<br><a href=\"\/2014\/07\/14\/max7219-driver-for-led-matrix-8x8\/\">MAX7219 driver for LED Matrix 8\u00d78<\/a>.<\/p>\n\n\n\n<p><br><\/p>\n","protected":false},"excerpt":{"rendered":"<p>UPDATE 2022: The MAX7219LED8x8 library, now renamed to MAX7219tiny has now a new home at tinusaur.com\/libraries\/max7219tiny. Check also this&nbsp;MAX7219 &amp; ATtiny85 tutorial&nbsp;to learn how the library works. The\u00a0MAX7219\u00a0controller manufactured by\u00a0Maxim Integrated\u00a0is\u00a0a compact, serial input\/output common-cathode display driver that could interface microcontrollers to 64 individual LEDs, 7-segment numeric LED displays of up to 8 digits, bar-graph &#8230; <a title=\"Interfacing a MAX7219 Driven LED Matrix with ATtiny85\" class=\"read-more\" href=\"https:\/\/tinusaur.org\/2019\/01\/06\/interfacing-a-max7219-driven-led-matrix-with-attiny85\/\" aria-label=\"Read more about Interfacing a MAX7219 Driven LED Matrix with ATtiny85\">Read more<\/a><\/p>\n","protected":false},"author":54,"featured_media":2906,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3,16],"tags":[32,78,93,116,120,127,128,173],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v22.3 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Interfacing a MAX7219 Driven LED Matrix with ATtiny85 - The Tinusaur Project<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/tinusaur.org\/2019\/01\/06\/interfacing-a-max7219-driven-led-matrix-with-attiny85\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Interfacing a MAX7219 Driven LED Matrix with ATtiny85 - The Tinusaur Project\" \/>\n<meta property=\"og:description\" content=\"UPDATE 2022: The MAX7219LED8x8 library, now renamed to MAX7219tiny has now a new home at tinusaur.com\/libraries\/max7219tiny. Check also this&nbsp;MAX7219 &amp; ATtiny85 tutorial&nbsp;to learn how the library works. The\u00a0MAX7219\u00a0controller manufactured by\u00a0Maxim Integrated\u00a0is\u00a0a compact, serial input\/output common-cathode display driver that could interface microcontrollers to 64 individual LEDs, 7-segment numeric LED displays of up to 8 digits, bar-graph ... 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