{"product_id":"20x4-i2c-character-lcd-display-module-lcd2004-pcf8574-backpack-pre-soldered","title":"20x4 I2C Character LCD Display Module (LCD2004 + PCF8574 Backpack, Pre-Soldered)","description":"\u003ch1\u003e20x4 I2C Character LCD Display Module (LCD2004 + PCF8574, Pre-Soldered)\u003c\/h1\u003e\u003cp\u003eA 20x4 LCD2004 HD44780 character display with a PCF8574 I2C backpack \u003cstrong\u003ealready soldered on\u003c\/strong\u003e. Four rows of twenty characters over just two signal wires (SDA + SCL), instead of the six GPIO a bare parallel panel needs — and no soldering to do.\u003c\/p\u003e\u003ch2\u003eWhy the I2C version\u003c\/h2\u003e\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eWiring\u003c\/th\u003e\n\u003cth\u003eParallel LCD2004\u003c\/th\u003e\n\u003cth\u003eThis module\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eSignal pins used\u003c\/td\u003e\n\u003ctd\u003e6 (RS, EN, D4–D7)\u003c\/td\u003e\n\u003ctd\u003e2 (SDA, SCL)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eContrast pot\u003c\/td\u003e\n\u003ctd\u003eExternal 10k required\u003c\/td\u003e\n\u003ctd\u003eOn-board trimpot\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAssembly\u003c\/td\u003e\n\u003ctd\u003eSolder a backpack on\u003c\/td\u003e\n\u003ctd\u003eNone — ready to wire\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\u003ch2\u003eKey Specifications\u003c\/h2\u003e\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eSpecification\u003c\/th\u003e\n\u003cth\u003eValue\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eDisplay\u003c\/td\u003e\n\u003ctd\u003e20 characters x 4 rows, HD44780-compatible\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eInterface\u003c\/td\u003e\n\u003ctd\u003eI2C (PCF8574 expander)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDefault I2C address\u003c\/td\u003e\n\u003ctd\u003e0x27 (PCF8574T). Some batches use PCF8574AT at 0x3F — scan to confirm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAddress select\u003c\/td\u003e\n\u003ctd\u003eA0\/A1\/A2 solder jumpers\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOperating voltage\u003c\/td\u003e\n\u003ctd\u003e5V\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eLogic level\u003c\/td\u003e\n\u003ctd\u003e5V (use a level shifter on a 3.3V board such as ESP32)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eI2C speed\u003c\/td\u003e\n\u003ctd\u003e100 kHz standard mode only (PCF8574 limit — not 400 kHz)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eContrast\u003c\/td\u003e\n\u003ctd\u003eOn-board potentiometer\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePins\u003c\/td\u003e\n\u003ctd\u003eVCC, GND, SDA, SCL\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\u003ch2\u003eWiring\u003c\/h2\u003e\u003cp\u003eArduino Uno: SDA to A4, SCL to A5. ESP32: SDA to GPIO21, SCL to GPIO22. VCC to 5V, GND to GND.\u003c\/p\u003e\u003ch2\u003eCode\u003c\/h2\u003e\u003cp\u003eUse the \u003cstrong\u003eLiquidCrystal_I2C\u003c\/strong\u003e library (Frank de Brabander). Construct it as \u003ccode\u003eLiquidCrystal_I2C lcd(0x27, 20, 4);\u003c\/code\u003e — note the 20 and 4 — then \u003ccode\u003elcd.init();\u003c\/code\u003e and \u003ccode\u003elcd.backlight();\u003c\/code\u003e. \u003ccode\u003einit()\u003c\/code\u003e returns void, so never test it inside an \u003ccode\u003eif\u003c\/code\u003e.\u003c\/p\u003e\u003ch2\u003eNotes\u003c\/h2\u003e\u003cp\u003eOnly dark blocks on screen means the contrast trimpot needs adjusting. Nothing at all usually means the wrong I2C address — run a scanner; it is 0x27 on most units and 0x3F on PCF8574AT variants.\u003c\/p\u003e","brand":"Compoden","offers":[{"title":"Default Title","offer_id":53617529913709,"sku":"CDN-LCD-I2C-2004-DRAFT","price":388.0,"currency_code":"INR","in_stock":true}],"url":"https:\/\/compoden.com\/products\/20x4-i2c-character-lcd-display-module-lcd2004-pcf8574-backpack-pre-soldered","provider":"Compoden","version":"1.0","type":"link"}