liblinht-ctrl

A modular C library for controlling GPIO pins and PWM channels on LinHT

Building

# Build both static and shared libraries
make

# Build example program
make example

# Clean build artifacts
make clean

# Install to system (requires sudo)
sudo make install

# Uninstall from system
sudo make uninstall

# Show help
make help

Build Outputs

• liblinht-ctrl.a - Static library
• liblinht-ctrl.so - Shared library
• example - Example program (when built)

Usage

#include <liblinht-ctrl.h>

int main(void)
{
    // Control flashlight
    linht_ctrl_flashlight_set(true);   // Turn on
    linht_ctrl_flashlight_set(false);  // Turn off
    
    // Control LEDs
    linht_ctrl_green_led_set(true);
    linht_ctrl_red_led_set(true);
    
    // Set LCD backlight to 50% brightness
    linht_ctrl_lcd_backlight_set_brightness(128);
    
    // Set keyboard backlight to full brightness
    linht_ctrl_kbd_backlight_on();
    
    return 0;
}

API Reference

GPIO Functions

Specific GPIO Controls

Pre-configured functions for common hardware controls. These handle chip selection internally.

int linht_ctrl_flashlight_set(bool state);

Control the device flashlight (GPIO2 pin 18).

• Parameters: state - true to turn on, false to turn off
• Returns: 0 on success, -1 on error

int linht_ctrl_green_led_set(bool state);
int linht_ctrl_red_led_set(bool state);

Control the status LEDs (GPIO2 pins 4 and 5).

• Parameters: state - true to turn on, false to turn off
• Returns: 0 on success, -1 on error

int linht_ctrl_tx_rx_switch_set(bool tx_mode);

Control the TX/RX RF switch (GPIO2 pin 13).

• Parameters: tx_mode - true for TX mode, false for RX mode
• Returns: 0 on success, -1 on error

Generic GPIO Control

Direct control of any GPIO pin on any chip with full configuration options.

int linht_ctrl_gpio_set(const char* gpio_chip_path, uint16_t pin_offset, bool state);

Set the state of a GPIO pin.

• Parameters:
  • gpio_chip_path - Path to GPIO chip (e.g., LINHT_CTRL_GPIO2_PATH)
  • pin_offset - Pin number on the chip
  • state - true for active, false for inactive
• Returns: 0 on success, -1 on error

int linht_ctrl_gpio_configure(const char* gpio_chip_path, uint16_t pin_offset,
                              const linht_ctrl_gpio_config_t* config);

Configure a GPIO pin with custom settings.

• Parameters:
  • gpio_chip_path - Path to GPIO chip
  • pin_offset - Pin number on the chip
  • config - Configuration structure with direction, bias, and active level
• Returns: 0 on success, -1 on error

GPIO Configuration Structure:

typedef struct {
    linht_ctrl_gpio_direction_t direction;  // INPUT or OUTPUT
    linht_ctrl_gpio_bias_t bias;            // DISABLED, PULL_UP, or PULL_DOWN
    linht_ctrl_gpio_active_t active_level;  // ACTIVE_HIGH or ACTIVE_LOW
} linht_ctrl_gpio_config_t;

PWM Functions

Backlight Controls

Convenient functions for LCD and keyboard backlight management.

int linht_ctrl_lcd_backlight_set_brightness(uint8_t brightness);
int linht_ctrl_kbd_backlight_set_brightness(uint8_t brightness);

Set backlight brightness.

• Parameters: brightness - 0 (off) to 255 (maximum)
• Returns: 0 on success, -1 on error

int linht_ctrl_lcd_backlight_on(void);
int linht_ctrl_kbd_backlight_on(void);

Turn backlight on at full brightness (255).

• Returns: 0 on success, -1 on error

int linht_ctrl_lcd_backlight_off(void);
int linht_ctrl_kbd_backlight_off(void);

Turn backlight off (brightness 0).

• Returns: 0 on success, -1 on error

Generic PWM Control

Direct control of PWM channels for custom applications.

int linht_ctrl_pwm_export(uint8_t channel);

Export a PWM channel for use.

• Parameters: channel - PWM channel number
• Returns: 0 on success, -1 on error

int linht_ctrl_pwm_unexport(uint8_t channel);

Unexport a PWM channel.

• Parameters: channel - PWM channel number
• Returns: 0 on success, -1 on error

int linht_ctrl_pwm_enable(uint8_t channel);
int linht_ctrl_pwm_disable(uint8_t channel);

Enable or disable PWM output.

• Parameters: channel - PWM channel number
• Returns: 0 on success, -1 on error

int linht_ctrl_pwm_configure(uint8_t channel, uint32_t period_ns, uint8_t duty_cycle);

Configure PWM period and duty cycle.

• Parameters:
  • channel - PWM channel number
  • period_ns - Period in nanoseconds (default: 50000 for 20kHz)
  • duty_cycle - Duty cycle percentage (0-100)
• Returns: 0 on success, -1 on error