What it is
The ShillehTek PCF8574 I2C Serial Interface Adapter Module for 1602 2004 LCD converts a typical 16‑pin parallel character LCD into a simple two‑wire I2C connection (SDA/SCL), helping Arduino and other microcontroller projects save GPIO while simplifying wiring. It solders to the LCD header, includes a contrast potentiometer, supports address changes via A0/A1/A2 solder pads, and can disable the backlight by removing the jumper cap.
Pins
This module is commonly used with I2C lines (SDA and SCL) plus power connections, and it interfaces to the LCD through the standard 16‑pin header on 1602/2004 character displays. For exact pin names and header orientation on your revision, refer to the silkscreen labels on the board/module and the listing photos.
Technical Specifications
| Item | Details |
|---|---|
| Interface type | I2C (two-wire) via PCF8574 |
| Compatible displays | 1602 (16x2) and 2004 (20x4) character LCD modules |
| LCD connection | Solders to the display’s 16-pin header (LCD backpack style) |
| I2C address options | Default often 0x27 or 0x3F; adjustable via A0/A1/A2 solder pads |
| Contrast adjustment | Onboard potentiometer |
| Backlight control | Backlight jumper cap removable to disable LED backlight |
Frequently Asked Questions
How do I connect a PCF8574 I2C LCD backpack to an Arduino?
Connect the module to your Arduino’s I2C pins (SDA and SCL) plus power, then connect it to the 1602/2004 LCD via the 16-pin header. After wiring, use an I2C LCD library and set the correct I2C address.
What I2C address does the PCF8574 LCD adapter use (0x27 vs 0x3F)?
Many modules default to 0x27 or 0x3F depending on the PCF8574 variant and board revision. If your display doesn’t respond, run an I2C scanner sketch and then set your library to the detected address.
How do I change the I2C address with A0/A1/A2 pads?
Use the A0/A1/A2 solder pads to modify the address so multiple LCDs can share one I2C bus. After changing pads, rescan the bus to confirm the new address and update your code accordingly.
How do I adjust contrast on a 1602/2004 LCD with this I2C adapter?
Use the onboard potentiometer (trim knob) to tune contrast until characters are clearly visible. Small adjustments can make a big difference, especially after first power-up.
Can I turn off the LCD backlight to reduce power?
Yes—this adapter includes a backlight jumper cap. Remove the jumper to disable the LED backlight when lower power or reduced brightness is desired.