16×2 or 20×4?

A 16×2 shows 32 characters and fits a small enclosure. A 20×4 shows 80 characters, enough for a label plus value on every line or a simple menu. The 20×4 is roughly twice the panel area and draws more backlight current, so size it to the information, not the price.

I2C Backpack Type

Most modules use a PCF8574 I/O expander and work with the standard LiquidCrystal_I2C library. Integrated or RGB controllers (AiP31068L, ATmega328P) need the vendor’s library instead. Check which one you are buying before you copy example code.

5 V vs 3.3 V Logic

Classic blue modules want 5 V for good contrast. On an ESP32, ESP8266 or Pico, power the LCD from 5 V and either add a level shifter or remove the backpack pull-ups. Waveshare and SparkFun modules are designed for 3.3 V systems out of the box.

I2C Address

PCF8574T backpacks usually answer at 0x27, PCF8574AT at 0x3F. Solder jumpers A0 to A2 let you change it, which is how you run several LCDs on one bus. Always run an I2C scanner sketch first instead of guessing.

Backlight & Contrast

Blue with white text is the most common and easy to read indoors. Yellow-green reads better in sunlight. Make sure there is an accessible contrast pot and a backlight jumper so you can cut power in battery projects.

The GeeekPi 2-Pack is the sensible buy if you have more than one project on the go or want a spare for the inevitable reverse-polarity accident. Each module is the familiar 16×2 blue panel with a PCF8574 backpack at 0x27, a contrast and backlight potentiometer, and a 5 V supply requirement, so every LiquidCrystal_I2C example works unchanged. GeeekPi lists compatibility with Arduino, Raspberry Pi, Tinker Board, NanoPi, Banana Pi and STM32, and the module measures about 80 × 35 × 11 mm. It is also one of the best-rated listings in the category at around 4.6 stars from several hundred buyers.

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Freenove’s “New Type” I2C LCD 1602 integrates the I2C conversion circuit on the module rather than using a separate soldered-on backpack, which Freenove says makes it more stable. The real reason to buy it is support: Freenove provides example projects and code for Arduino, Raspberry Pi, Raspberry Pi Pico and ESP32, with the tutorial link printed on the box. If you are following a Freenove kit or teaching a class across several platforms, that matching code saves real time. Because the controller differs from the classic PCF8574 backpack, use Freenove’s provided library and examples rather than assuming a generic sketch will work.

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Need several 20×4 displays for a classroom, a set of sensor nodes or a few test fixtures? The Hosyond 3-pack gives you three 2004 modules, each with an I2C backpack at 0x27, a 5 V supply and a backlight potentiometer on the back. Hosyond even prints the Uno wiring on the listing (SDA to A4, SCL to A5). The multipack also hedges against the occasional weak unit you get with budget LCDs, and the listing holds around 4.7 stars from close to two hundred ratings, which is high for this category.

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If you need exactly one 20×4 for a one-off build, the GeeekPi I2C 2004 is a lower-cost alternative to the SunFounder. It is the same idea: a 20×4 blue character panel with an I2C interface adapter, compatible with anything that speaks I2C, from Arduino and Raspberry Pi to ESP32 and STM32. GeeekPi includes jumper wires in the box, so you can wire it straight to a dev board. Amazon ratings sit around 4.6 stars, although GeeekPi’s listing copy is thin on electrical detail, so plan to run an I2C scanner before you hard-code the address.

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The Waveshare LCD1602 RGB is the module to pick when you want colour or a clean 3.3 V design. Instead of a PCF8574 backpack, it uses an onboard AiP31068L LCD controller and a PCA9633 RGB driver, giving you software control of up to 16 million backlight colours over I2C. That makes the backlight itself an indicator: green for OK, amber for warning, red for fault. It is specified for both 3.3 V and 5 V operation, so it drops straight onto a Raspberry Pi, Pi Pico, Jetson Nano or ESP32 without level shifting, and Waveshare publishes demo code for all of them. Amazon reviews are more mixed (around 3.9 stars), mostly from buyers who tried generic LiquidCrystal_I2C code, which will not drive this controller.

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The SparkFun SerLCD is a different class of product: an ATmega328P on the back of the display handles all the LCD control, so your microcontroller just sends text over Serial, I2C or SPI. The I2C address (default 0x72) can be changed in software, backlight brightness and contrast are set by PWM from code instead of a potentiometer, there is an 80-character input buffer and a user-definable splash screen. The Qwiic connector means no soldering if you already use SparkFun or Adafruit STEMMA QT boards, and the firmware is open source and reflashable from the Arduino IDE. It is the most expensive pick here, but it is also the least fiddly.

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First LCD for an Arduino Uno?

Get the SunFounder I2C LCD1602. Four wires, address 0x27, and every LiquidCrystal_I2C tutorial works first time.

Building a dashboard or menu?

Text that does not fit in 32 characters needs the SunFounder I2C 2004. Four lines covers a title plus three live values.

Several projects or a classroom?

Buy packs. The GeeekPi 2-Pack for 16×2 or the Hosyond 3-Pack for 20×4 gives you the lowest cost per display plus spares.

Learning on ESP32 or Pi Pico?

The Freenove New Type 1602 ships with example code for Arduino, Pi, Pico and ESP32, which saves hours of porting.

Need colour status or 3.3 V logic?

The Waveshare LCD1602 RGB runs natively at 3.3 V and turns the backlight into a red, amber or green indicator.

Using Qwiic or STEMMA QT boards?

The SparkFun SerLCD plugs straight in, supports Serial, I2C and SPI, and sets contrast in software.

My I2C LCD lights up but shows nothing, or only a row of boxes. What is wrong?

Nine times out of ten it is the contrast potentiometer. Turn the small blue pot on the back slowly with a screwdriver while the sketch runs until the characters appear. A top row of solid boxes means the LCD has power but has not been initialised, which points to the wrong I2C address or wrong SDA/SCL pins. On an Uno, SDA is A4 and SCL is A5; on an ESP32 the defaults are GPIO 21 and 22. If you power a 5 V module from 3.3 V you may also see faint or no text, because the glass needs around 5 V for proper contrast.

Is my LCD at address 0x27 or 0x3F?

It depends on the backpack chip. Modules with a PCF8574T usually answer at 0x27, those with a PCF8574AT at 0x3F, and the A0 to A2 solder pads shift the address within that range. Do not guess: upload an I2C scanner sketch, open the serial monitor and use whatever address it reports. RGB and smart modules such as the Waveshare RGB and SparkFun SerLCD use their own fixed or software-set addresses (SparkFun defaults to 0x72).

Can I use a 16×2 I2C LCD with an ESP32, ESP8266 or Raspberry Pi Pico?

Yes, and it is very common, but be aware of the voltage mismatch. Standard blue modules need 5 V for good contrast, and the backpack’s pull-up resistors then pull SDA and SCL to 5 V, which exceeds the official rating of 3.3 V microcontrollers. The robust options are a small bidirectional I2C level shifter, removing the backpack pull-ups and relying on 3.3 V pull-ups, or choosing a module designed for 3.3 V such as the Waveshare LCD1602 RGB or SparkFun SerLCD. Our ESP32 and ESP8266 I2C LCD tutorial walks through the wiring and code.

Should I choose a 16×2 LCD, a 20×4 LCD or an OLED?

Pick a 16×2 when you only show one or two values and space is tight. Pick a 20×4 for menus, multi-sensor readouts or status pages, since four lines of twenty characters is two and a half times the text. Choose an OLED or TFT when you need graphics, icons or very low power with the backlight off. Character LCDs still win on cost, sunlight readability with a backlight, and the simplicity of a text-only API, which is why they remain standard in test fixtures and industrial panels.

Can I connect two or more I2C LCDs to the same Arduino?

Yes, as long as each one has a unique address. On PCF8574 backpacks, bridge one or more of the A0, A1 and A2 solder pads to move a module away from the default 0x27, giving up to eight displays per chip variant. Then create a separate LiquidCrystal_I2C object for each address. With several 5 V modules on one bus, keep wires short and remember each backpack adds its own pull-ups, so the combined resistance can get quite low; removing the extra pull-ups on all but one module keeps the bus healthy.