i2c-displayd - Man Page

I2C display controller for single board computers

Synopsis

i2c-displayd [-config path] [-mock] [-validate-config] [-test-display]

i2c-displayd drives small OLED and TFT displays attached to single board computers (Raspberry Pi, Rock 3C, etc.) over I2C or SPI. It shows rotating pages of system statistics (disk, RAM, CPU temperature) and network interface information.

Supported display types include SSD1306 (I2C), ST7735 (SPI), and UCTRONICS colour displays (I2C bridge).

Options

-config path: Path to a JSON configuration file. If not specified, the daemon searches for configuration in /etc/i2c-display/config.json, then falls back to built-in defaults.
-mock: Use a mock display for testing without hardware.
-validate-config: Validate the configuration file and exit. Returns exit code 0 if valid, non-zero otherwise.
-test-display: Run a hardware test pattern on the display and exit. Cycles through solid white, border rectangle, diagonal lines, text rendering, and clear.

Files

/etc/i2c-display/config.json: Default configuration file.
/usr/lib/systemd/system/i2c-display.service: Systemd service unit file.

Exit Status

0: Successful operation (or valid configuration with -validate-config).
non-zero: An error occurred during startup or configuration validation.

Examples

Run with a specific configuration file:

i2c-displayd -config /etc/i2c-display/config.json

Test display hardware:

i2c-displayd -config /etc/i2c-display/config.json -test-display

Validate configuration without starting the daemon:

i2c-displayd -config /etc/i2c-display/config.json -validate-config

Signals

SIGHUP: Reload configuration file without restarting the daemon.
SIGUSR1: Wake the display immediately if the screen saver is active. The display remains on for the configured wake_duration (default 30 seconds) before returning to normal screen saver behaviour. Equivalent to curl -X POST http://localhost:9090/wake when the metrics server is enabled.