{"id":1140,"date":"2024-06-23T17:37:56","date_gmt":"2024-06-23T17:37:56","guid":{"rendered":"https:\/\/iotthinghub.com\/?p=1140"},"modified":"2024-08-11T15:07:58","modified_gmt":"2024-08-11T15:07:58","slug":"twi-seven-segment-display","status":"publish","type":"post","link":"https:\/\/iotthinghub.com\/?p=1140","title":{"rendered":"TWI \u2013 Two Wire Interface"},"content":{"rendered":"\n

What is TWI? TWI stands for Two Wire Interface. We previously learn about segment display (SSD). SSD require many GPIO pin that could be used for any other purpose. We can use only 2 wires for up to 6SSD display at a same time. So only 2GPIO pins can be used for controlling up to 6 seven segment display. In that case we use a special IC TM1637. It will come with a compact package. TM1637 is a kind of LED(light emitting diode display) drive control special circuit with keyboard scan interface and it\u2019s internally integrated with MCU digital interface, data latch, LED high pressure drive and keyboard scan<\/p>\n\n\n\n

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Here the SSD are common anode type display. Let\u2019s look the datasheet how to interface.<\/p>\n\n\n\n

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Let\u2019s begin with start, stop and acknowledge function. First we make a function for some delay. Here we will not stop the processor by using _delay_ms<\/strong> or _delay_us<\/strong> function. We passing a loop without operation.<\/p>\n\n\n

\nvoid _cpu_delay(uint32_t i)\n{\n    while (i > 0) {\n    \tfor (uint32_t j = 0; j < 10; j++) {\n    \t\tasm("nop");\n    \t}\n    \ti--;\n    }\n}\n<\/pre><\/div>\n\n\n
For start condition first set both CLK and DIO pin high then set low the DIO pin. Program for the start condition<\/p>\n\n\n
\nvoid tm1637_Start(void)\n{\n\tTM1637_CLK_PORT|=(1<<TM1637_CLK_PIN); \/\/CLK pin low\n\tTM1637_DIO_PORT|=(1<<TM1637_DIO_PIN); \/\/DIO pin high\n\t_cpu_delay(5);\n\tTM1637_DIO_PORT&=~(1<<TM1637_DIO_PIN); \/\/DIO pin low\n}\n<\/pre><\/div>\n\n\n
For stop condition both the CLK and DIO pin set low. After a delay first set CLK pin to high again some delay set the DIO pin to high.<\/p>\n\n\n
\nvoid tm1637_Stop(void)\n{\n\tTM1637_CLK_PORT&=~(1<<TM1637_CLK_PIN); \/\/CLK pin low\n\t\/\/_cpu_delay(5);\n\tTM1637_DIO_PORT&=~(1<<TM1637_DIO_PIN); \/\/DIO pin low\n    _cpu_delay(5);\n    TM1637_CLK_PORT|=(1<<TM1637_CLK_PIN);  \/\/CLK pin high\n    _cpu_delay(5);\n    TM1637_DIO_PORT|=(1<<TM1637_DIO_PIN); \/\/DIO pin high\n}\n<\/pre><\/div>\n\n\n
For Read Acknowledge bit fist set the CLK pin low and DIO pin high. Set a delay time then read the pin of DIO pin. First set the CLK pin high then after a delay set the pin low.<\/p>\n\n\n
\nuint8_t tm1637_RACK(void)\n{\n\tTM1637_CLK_PORT&=~(1<<TM1637_CLK_PIN); \/\/CLK pin low\n\tTM1637_DIO_PORT|=(1<<TM1637_DIO_PIN);  \/\/DIO pin high\n\t_cpu_delay(7);\n    uint8_t u8_return = TM1637_DIO_PORT&(1<<TM1637_DIO_PIN);\n\tTM1637_CLK_PORT|=(1<<TM1637_CLK_PIN);  \/\/CLK pin high\n\t_cpu_delay(5);\n    TM1637_CLK_PORT&=~(1<<TM1637_CLK_PIN); \/\/CLK pin low\n    return u8_return;\n}\n<\/pre><\/div>\n\n\n
Now the important function is to transfer the data to IC. Here data is writing when CLK pin is at low state. Write procedure is to write 0th<\/sup> bit first then 1st<\/sup> then 2nd<\/sup> and so on. After data write set the CLK pin to high.<\/p>\n\n\n
\nvoid tm1637_WriteByte(uint8_t data)\n{\n    for (uint8_t i = 0; i < 8; i++) {\n    \tTM1637_CLK_PORT&=~(1<<TM1637_CLK_PIN);  \/\/CLK pin low\n        if (data & 0x01) {\n        \tTM1637_DIO_PORT|=(1<<TM1637_DIO_PIN);\/\/DIO pin high\n        } else {\n        \tTM1637_DIO_PORT&=~(1<<TM1637_DIO_PIN);\/\/DIO pin low\n        }\n        _cpu_delay(7);\n        data >>= 1;\n        TM1637_CLK_PORT|=(1<<TM1637_CLK_PIN); \/\/CLK pin low\n        _cpu_delay(7);\n    }\n}\n<\/pre><\/div>\n\n\n
We are done with data transfer basic now look at the command that will be set. Address command setting-<\/p>\n\n\n\n
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Since we use auto incremental method, so we need only one address 0xC0. We can control the brightness of the display.<\/p>\n\n\n\n
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We can write at a fixed address with data. We use fixed address mode for display brightness control.<\/p>\n\n\n
\n\/\/ Display control functions Brightness values: 1 - 7\nvoid tm1637_SetBrightness(uint8_t brightness)\n{\n\ttm1637_Start();\n\ttm1637_WriteByte(0x88+ (brightness&0x0f));\n\ttm1637_RACK();\n\ttm1637_Stop();\n}\n<\/pre><\/div>\n\n\n
Once we set our brightness now it is time to display some data on the SSDs. Follow the step and send data in a sequence. For fixed address mode 0x44 and automatic address adding is 0x40.<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n
\nvoid tm1637_DisplayUpdate(uint8_t data0,uint8_t data1,uint8_t data2,uint8_t data3)\n{\n\/\/--- Send Data register   \n\ttm1637_Start();\n\ttm1637_WriteByte(0x40);\/\/Memory write command\n    tm1637_RACK();\n    tm1637_Stop();\n\/\/--- Send First address\n    tm1637_Start();\n    tm1637_WriteByte(0xC0);\/\/Start address\n    tm1637_RACK();\n\/\/---  Send Data 1 by 1  \n\ttm1637_WriteByte(data0);\/\/Data\n    tm1637_RACK();\n\ttm1637_WriteByte(data1);\/\/Data\n    tm1637_RACK();\n\ttm1637_WriteByte(data2);\/\/Data\n    tm1637_RACK();\n\ttm1637_WriteByte(data3);\/\/Data\n    tm1637_RACK();\n\/\/--- Send Stop Condition for finished\n    tm1637_Stop();\n}\n<\/pre><\/div>\n\n\n
Our main program is to just display number and character.<\/p>\n\n\n
\n#include <avr\/io.h>\n#include <util\/delay.h>\nint main(void)\n{\n    init_tm1637();\n    while (1) \n    {\n\t\tdisplay_number(325,1);      \/\/ 4 digit number & 1 represents brightness level.\n        _delay_ms(3000);\n\t\tdisplay_char("Hello ..",1); \/\/ character available & 1 represents brightness level\n        _delay_ms(3000);\n    }\n}\n<\/pre><\/div>\n\n\n
You can interface 6 digits using TM1637 IC. In that case you can build your own PCB display control seven segment display.<\/p>\n\n\n\n
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download<\/a><\/div>\n<\/div>\n<\/div>\n\n\n\n
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Download the .hex with proteus simulation<\/a><\/strong><\/p>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"
What is TWI? TWI stands for Two Wire Interface. We previously learn about segment display (SSD). SSD require many GPIO pin that could be used for any other purpose. We can use only 2 wires for up to 6SSD display at a same time. So only 2GPIO pins can be used for controlling up to […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9],"tags":[],"class_list":["post-1140","post","type-post","status-publish","format-standard","hentry","category-i-o-port-operations"],"_links":{"self":[{"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/posts\/1140","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1140"}],"version-history":[{"count":19,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/posts\/1140\/revisions"}],"predecessor-version":[{"id":2554,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/posts\/1140\/revisions\/2554"}],"wp:attachment":[{"href":"https:\/\/iotthinghub.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1140"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1140"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1140"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}