{"id":2180,"date":"2024-07-15T15:56:33","date_gmt":"2024-07-15T15:56:33","guid":{"rendered":"https:\/\/iotthinghub.com\/?p=2180"},"modified":"2024-08-11T17:49:14","modified_gmt":"2024-08-11T17:49:14","slug":"i2c-lcd-pcf8574a","status":"publish","type":"post","link":"https:\/\/iotthinghub.com\/?p=2180","title":{"rendered":"I2C LCD (PCF8574A)"},"content":{"rendered":"\n

We already learn LCD interfacing in GPIO part. LCD Display requires lots of digital I\/O pin and the circuit requires more space. In market I2<\/sup>C LCD display are available and the interfacing is not so difficult. You just need the hardware and the I2<\/sup>C IC which is connected with that LCD. Usually in maximum I2<\/sup>C LCD module use PFC8574A. The PCF8574A is a I2<\/sup>C parallel port expander with latch outputs with high-current drive capability for directly driving LEDs. First look at the hardware how it is connected to LCD.<\/p>\n\n\n\n

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Here pins A2<\/sub>:A1<\/sub> are connected to Vcc<\/sub> via 1K\u03a9 resistance. SDA and SCL are internally pull-up by Vcc <\/sub>so no need for an extra pull-up resistors. Let\u2019s look at the I2<\/sup>C protocol provide by datasheet<\/p>\n<\/div>\n\n\n\n

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Here the logical address is 0111 and the physical address is 111 (since all pin are connected to Vcc<\/sub>). So the device has I2<\/sup>C address 0b0011 1111 or 0x3F. From the data sheet provided we need to start I2<\/sup>C then write the device address with write operation and send data. So our first step is to initialize the LCD ones with I2<\/sup>C start and device ADD+W then we just send data, no farther need of I2<\/sup>C start and device ADD+W command. We just need to change some user function in the LCD library. Let\u2019s go step by step. Since the device can work with 100KHz frequency.<\/p>\n\n\n\n

void system_init(void) -> I2<\/sup>C initialization function<\/p>\n\n\n

\nvoid system_init(void)\n{\n  TWSR=0x00;                \/\/--- Presclar = 1=4^0 \n  TWBR=0x20;                \/\/--- F_CPU=8MHz and Prescaler=1\n  TWCR=(1<<TWEN);           \/\/--- TWI Initialazion\n  TWCR=(1<<TWEN)|(1<<TWINT)|(1<<TWSTA); \/\/--- TWI Interrupt desable, TWI enable, TWI Start\n  while(!(TWCR&(1<<TWINT)));             \/\/--- Wait untial start condition is executed\n  twi_write(0x3F<<1 | 0);  \/\/PCF8574A---- Device ID-- 0b0111 1110\n  LCD_INIT();              \/\/LCD Initializion\n  _delay_ms(100);          \/\/Some delay for LCD initialization\n}\n<\/pre><\/div>\n\n\n
Let\u2019s look the write command or data function. For write command the R\/S pin remain 0 and EN pin goes from 1 to 0.<\/p>\n\n\n\n
void LCD_cmd(unsigned char cmd) -> write command format<\/p>\n\n\n
\nvoid LCD_cmd(unsigned char cmd)\n{\n  twi_write(cmd|0b00001100); \/\/ EN = 1 and Backlight ON(Pin \u2013P3)\n  _delay_ms(2);             \n  twi_write(cmd|0b00001000); \/\/EN = 0 and Backlight ON\n}\n<\/pre><\/div>\n\n\n
void nibble_cmd(unsigned char LCD_value)  -> write command<\/p>\n\n\n
\nvoid nibble_cmd(unsigned char LCD_value)\n{\n  unsigned char display_nibble;\n  display_nibble=LCD_value&0xF0;                 \/\/mask lower nibble because DD4-DD7 \n  pins are used\n  LCD_cmd(display_nibble);                       \/\/Send upper Nibble\n  display_nibble=((LCD_value<<4) & 0xF0);       \/\/mask the upper Nibble\n  LCD_cmd(display_nibble); \n}\n<\/pre><\/div>\n\n\n
Now for data send R\/S pin is 1 and EN pin goes from 1 to 0.<\/p>\n\n\n\n
void LCD_write(unsigned char data) -> write data format<\/p>\n\n\n
\nvoid LCD_write(unsigned char data)\n{\n  twi_write(data|0b00001101); \/\/ EN = 1, R\/S=1 and Backlight ON\n  _delay_ms(2);\n  twi_write(data|0b00001001); \/\/ EN = 0, R\/S=1 and Backlight ON\n}\n<\/pre><\/div>\n\n\n
void nibble_data(unsigned char LCD_data) ->  write data<\/p>\n\n\n
\nvoid nibble_data(unsigned char LCD_data)\n{\n  unsigned char data_nibble;\n  data_nibble=LCD_data&0xF0;                   \/\/mask lower nibble because DD4-DD7 pins are used\n  LCD_write(data_nibble);                      \/\/Send upper Nibble\n  data_nibble=((LCD_data<<4) & 0xF0);         \/\/mask the upper Nibble\n  LCD_write(data_nibble); \n}\n<\/pre><\/div>\n\n\n
LCD other function remain the same. Download the I2CLCD.c and I2CLCD.h file, the main program as follow-<\/p>\n\n\n
\n  #include<avr\/io.h>\n  #include<util\/delay.h>\n  #include<util\/twi.h>\n  #include"I2CLCD.h"\nint main(void)\n  {\n   system_init();\n   LCD_write_string(1,2,"RUET EEE 091109");\n   while(1)\n     {\n       LCD_write_string(1,1,"Subeer kumar Sarkar");\n       _delay_ms(500);\n       LCD_Display_Right();\n     }\n return 0;\n}\n<\/pre><\/div>\n\n\n
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If you don\u2019t see the character on the display rotates the potentiometer of the I2<\/sup>C LCD. The connection as shown in the figure.<\/p>\n<\/div>\n\n\n\n
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download<\/a><\/div>\n<\/div>\n<\/div>\n\n\n\n
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I2C LCD.rar<\/a><\/p>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"
We already learn LCD interfacing in GPIO part. LCD Display requires lots of digital I\/O pin and the circuit requires more space. In market I2C LCD display are available and the interfacing is not so difficult. You just need the hardware and the I2C IC which is connected with that LCD. Usually in maximum I2C […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[19],"tags":[],"class_list":["post-2180","post","type-post","status-publish","format-standard","hentry","category-i2c"],"_links":{"self":[{"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/posts\/2180","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=2180"}],"version-history":[{"count":15,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/posts\/2180\/revisions"}],"predecessor-version":[{"id":2644,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/posts\/2180\/revisions\/2644"}],"wp:attachment":[{"href":"https:\/\/iotthinghub.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2180"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2180"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2180"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}