i2c / SPI Character LCD Backpack - STEMMA QT / Qwiic
I2C/SPI backpack for HD44780-compatible character LCDs, reducing control to 2 pins (I2C) or 3 pins (SPI). Includes 5-pin terminal block for wiring and STEMMA QT/Qwiic connector. Compatible with Adafruit's character LCD library for Arduino and CircuitPython.
Pinout
2 grouped source records are expanded into separate logical pads where unambiguous; physical placement is not implied.
- VIN
Power input for the I2C/SPI LCD backpack; Adafruit states it can be powered with 3 to 5V DC.
Type · PowerVoltage · 3-5V DC - GND
Ground reference for backpack power and logic.
Type · GroundVoltage · 0V - CLKSCLSCK
Clock line. In I2C mode this is SCL; after closing the SPI Enable jumper it is the SPI SCK clock input.
Type · I2C, SPI, SignalVoltage · 3-5V logic level shifted - DATSDAMOSI
Data line. In I2C mode this is SDA; after closing the SPI Enable jumper it is SPI MOSI, used to send data from the microcontroller to the backpack.
Type · I2C, SPI, SignalVoltage · 3-5V logic level shifted - LAT
SPI latch input used when the backpack is configured for SPI by soldering the SPI Enable jumper.
Type · Signal - SPI Enable jumper
Back-side solder jumper that enables SPI control instead of the default I2C interface.
Type · Control - LCD connector pins 1-16
Sixteen output pins along the top of the board for attaching a character LCD; Adafruit states pin 1 is furthest left when viewing the front/logo side.
Type · Unknown - Address jumpers
I2C address-selection jumpers used to chain up to 8 backpacks on the same I2C clock/data pins.
Type · Control - 3-5V jumper
Back-side jumper between the CLK and 3-5V labels used for board voltage configuration per the Adafruit pinouts page.
Type · ControlVoltage · 3-5V
| Pin | Type | Function | Voltage |
|---|---|---|---|
| VIN | Power | Power input for the I2C/SPI LCD backpack; Adafruit states it can be powered with 3 to 5V DC. | 3-5V DC |
| GND | Ground | Ground reference for backpack power and logic. | 0V |
| CLKSCLSCK | I2C, SPI, Signal | Clock line. In I2C mode this is SCL; after closing the SPI Enable jumper it is the SPI SCK clock input. | 3-5V logic level shifted |
| DATSDAMOSI | I2C, SPI, Signal | Data line. In I2C mode this is SDA; after closing the SPI Enable jumper it is SPI MOSI, used to send data from the microcontroller to the backpack. | 3-5V logic level shifted |
| LAT | Signal | SPI latch input used when the backpack is configured for SPI by soldering the SPI Enable jumper. | |
| SPI Enable jumper | Control | Back-side solder jumper that enables SPI control instead of the default I2C interface. | |
| LCD connector pins 1-16 | Unknown | Sixteen output pins along the top of the board for attaching a character LCD; Adafruit states pin 1 is furthest left when viewing the front/logo side. | |
| Address jumpers | Control | I2C address-selection jumpers used to chain up to 8 backpacks on the same I2C clock/data pins. | |
| 3-5V jumper | Control | Back-side jumper between the CLK and 3-5V labels used for board voltage configuration per the Adafruit pinouts page. | 3-5V |
2 grouped source records are expanded into separate logical pads where unambiguous; physical placement is not implied.
Pin details
9 connections- VIN
Power input for the I2C/SPI LCD backpack; Adafruit states it can be powered with 3 to 5V DC.
PowerVoltage · 3-5V DC - GND
Ground reference for backpack power and logic.
GroundVoltage · 0V - CLKSCLSCK
Clock line. In I2C mode this is SCL; after closing the SPI Enable jumper it is the SPI SCK clock input.
I2C, SPI, SignalVoltage · 3-5V logic level shifted - DATSDAMOSI
Data line. In I2C mode this is SDA; after closing the SPI Enable jumper it is SPI MOSI, used to send data from the microcontroller to the backpack.
I2C, SPI, SignalVoltage · 3-5V logic level shifted - LAT
SPI latch input used when the backpack is configured for SPI by soldering the SPI Enable jumper.
Signal - SPI Enable jumper
Back-side solder jumper that enables SPI control instead of the default I2C interface.
Control - LCD connector pins 1-16
Sixteen output pins along the top of the board for attaching a character LCD; Adafruit states pin 1 is furthest left when viewing the front/logo side.
Unknown - Address jumpers
I2C address-selection jumpers used to chain up to 8 backpacks on the same I2C clock/data pins.
Control - 3-5V jumper
Back-side jumper between the CLK and 3-5V labels used for board voltage configuration per the Adafruit pinouts page.
ControlVoltage · 3-5V
Start wiring
SPI · I2C · 3.3 V · 3.3 – 5 V · Breakout
Adafruit describes product 398 as a 16x2 RGB backlight LCD using digital pins for LCD control and PWM pins for the backlight; the product…
Module pins: VIN, GND, CLK / SCL / SCK, DAT / SDA / MOSI, LAT. Schematik maps them to your board in the app.
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