qmk_firmware/example_integration/lcd_backlight_hal.c

/*
The MIT License (MIT)

Copyright (c) 2016 Fred Sundvik

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

#include "lcd_backlight.h"
#include "hal.h"

#define RED_PIN 1
#define GREEN_PIN 2
#define BLUE_PIN 3
#define CHANNEL_RED FTM0->CHANNEL[0]
#define CHANNEL_GREEN FTM0->CHANNEL[1]
#define CHANNEL_BLUE FTM0->CHANNEL[2]

#define RGB_PORT PORTC
#define RGB_PORT_GPIO GPIOC

// Base FTM clock selection (72 MHz system clock)
// @ 0xFFFF period, 72 MHz / (0xFFFF * 2) = Actual period
// Higher pre-scalar will use the most power (also look the best)
// Pre-scalar calculations
// 0 -      72 MHz -> 549 Hz
// 1 -      36 MHz -> 275 Hz
// 2 -      18 MHz -> 137 Hz
// 3 -       9 MHz ->  69 Hz (Slightly visible flicker)
// 4 -   4 500 kHz ->  34 Hz (Visible flickering)
// 5 -   2 250 kHz ->  17 Hz
// 6 -   1 125 kHz ->   9 Hz
// 7 - 562 500  Hz ->   4 Hz
// Using a higher pre-scalar without flicker is possible but FTM0_MOD will need to be reduced
// Which will reduce the brightness range
#define PRESCALAR_DEFINE 0

void lcd_backlight_hal_init(void) {
	// Setup Backlight
    SIM->SCGC6 |= SIM_SCGC6_FTM0;
    FTM0->CNT = 0; // Reset counter

	// PWM Period
	// 16-bit maximum
	FTM0->MOD = 0xFFFF;

	// Set FTM to PWM output - Edge Aligned, Low-true pulses
#define CNSC_MODE FTM_SC_CPWMS | FTM_SC_PS(4) | FTM_SC_CLKS(0)
	CHANNEL_RED.CnSC = CNSC_MODE;
	CHANNEL_GREEN.CnSC = CNSC_MODE;
	CHANNEL_BLUE.CnSC = CNSC_MODE;

	// System clock, /w prescalar setting
	FTM0->SC = FTM_SC_CLKS(1) | FTM_SC_PS(PRESCALAR_DEFINE);

	CHANNEL_RED.CnV = 0;
	CHANNEL_GREEN.CnV = 0;
	CHANNEL_BLUE.CnV = 0;

	RGB_PORT_GPIO->PDDR |= (1 << RED_PIN);
	RGB_PORT_GPIO->PDDR |= (1 << GREEN_PIN);
	RGB_PORT_GPIO->PDDR |= (1 << BLUE_PIN);

#define RGB_MODE PORTx_PCRn_SRE | PORTx_PCRn_DSE | PORTx_PCRn_MUX(4)
    RGB_PORT->PCR[RED_PIN] = RGB_MODE;
    RGB_PORT->PCR[GREEN_PIN] = RGB_MODE;
    RGB_PORT->PCR[BLUE_PIN] = RGB_MODE;
}

void lcd_backlight_hal_color(uint16_t r, uint16_t g, uint16_t b) {
	CHANNEL_RED.CnV = r;
	CHANNEL_GREEN.CnV = g;
	CHANNEL_BLUE.CnV = b;
}