20x4 I2C Character LCD Display Module (LCD2004 + PCF8574 Backpack, Pre-Soldered)
20x4 I2C Character LCD Display Module (LCD2004 + PCF8574, Pre-Soldered)
A 20x4 LCD2004 HD44780 character display with a PCF8574 I2C backpack already soldered on. 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.
Why the I2C version
| Wiring | Parallel LCD2004 | This module |
|---|---|---|
| Signal pins used | 6 (RS, EN, D4–D7) | 2 (SDA, SCL) |
| Contrast pot | External 10k required | On-board trimpot |
| Assembly | Solder a backpack on | None — ready to wire |
Key Specifications
| Specification | Value |
|---|---|
| Display | 20 characters x 4 rows, HD44780-compatible |
| Interface | I2C (PCF8574 expander) |
| Default I2C address | 0x27 (PCF8574T). Some batches use PCF8574AT at 0x3F — scan to confirm |
| Address select | A0/A1/A2 solder jumpers |
| Operating voltage | 5V |
| Logic level | 5V (use a level shifter on a 3.3V board such as ESP32) |
| I2C speed | 100 kHz standard mode only (PCF8574 limit — not 400 kHz) |
| Contrast | On-board potentiometer |
| Pins | VCC, GND, SDA, SCL |
Wiring
Arduino Uno: SDA to A4, SCL to A5. ESP32: SDA to GPIO21, SCL to GPIO22. VCC to 5V, GND to GND.
Code
Use the LiquidCrystal_I2C library (Frank de Brabander). Construct it as LiquidCrystal_I2C lcd(0x27, 20, 4); — note the 20 and 4 — then lcd.init(); and lcd.backlight();. init() returns void, so never test it inside an if.
Notes
Only 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.
Ask Soldr above what you can build with this — it knows every Compoden kit this part appears in.
Shipping Information
- Prepaid Orders: ₹75 for orders up to ₹999, FREE shipping above ₹999
- COD Orders: ₹125 shipping + ₹50 COD fee = ₹175 total
- Delivery Timeline: Dispatch in 1-2 days, delivery in 2-7 days depending on location
Returns & Warranty
- 7-Day Return: Manufacturing defects only (approval required)
- Warranty: 7 days from delivery
- Non-Returnable: Batteries, consumables, cut wires, clearance items