Adding 16-bit brightness control to LCD backlight

Scan/STLcd/capabilities.kll

@@ -0,0 +1,44 @@
+Name = STLcdCapabilities;
+Version = 0.1;
+Author = "HaaTa (Jacob Alexander) 2015";
+KLL = 0.3c;
+
+# Modified Date
+Date = 2015-08-01;
+
+# Defines available to the STLcd sub-module
+
+# PWM Prescalar
+# In general this can be left alone
+# A higher prescalar should be lower power usage (less switching)
+# However, flickering may be noticeable.
+#
+# Here's a calculation table valid at a 72 MHz system clock
+# Prescalars range from 0 to 7 (1 to 128)
+# 0 -      72 MHz - Highest power usage/best result
+# 1 -      36 MHz
+# 2 -      18 MHz
+# 3 -       9 MHz - Slightly visible flicker (peripheral vision)
+# 4 -   4 500 kHz - Visible flickering
+# 5 -   2 250 kHz
+# 6 -   1 125 kHz
+# 7 - 562 500  Hz
+# Defaulting to no prescalar, looks the best
+STLcdBacklightPrescalar => STLcdBacklightPrescalar_define;
+STLcdBacklightPrescalar = 0;
+
+# Default Backlight Channel Brightness
+# There are 3 channels, RGB
+# In order to get other colors you must mix the 3 colors
+# Each channel is a 16-bit register (65536 levels)
+# Technically, this means, the backlight is a 48-bit RGB pixel
+# In practice, it may be difficult to get color consistency at times if too bright or too dim
+STLcdBacklightRed   => STLcdBacklightRed_define;
+STLcdBacklightGreen => STLcdBacklightGreen_define;
+STLcdBacklightBlue  => STLcdBacklightBlue_define;
+
+# Defaults to 6% brightness, white
+STLcdBacklightRed   = 0xFFF;
+STLcdBacklightGreen = 0xFFF;
+STLcdBacklightBlue  = 0xFFF;
+

Scan/STLcd/lcd_scan.c

@@ -21,6 +21,7 @@
 
 // Project Includes
 #include <cli.h>
+#include <kll.h>
 #include <led.h>
 #include <print.h>
 
@@ -276,16 +277,49 @@ inline void LCD_setup()
 
 	// Setup Backlight
 	// TODO Expose default settings
-	// TODO Setup PWM
+	SIM_SCGC6 |= SIM_SCGC6_FTM0;
-	GPIOC_PDDR |= (1<<1);
+	FTM0_CNT = 0; // Reset counter
-	PORTC_PCR1 = PORT_PCR_SRE | PORT_PCR_DSE | PORT_PCR_MUX(1);
+
-	GPIOC_PCOR |= (1<<1);
+	// PWM Period
-	GPIOC_PDDR |= (1<<2);
+	// 16-bit maximum
-	PORTC_PCR2 = PORT_PCR_SRE | PORT_PCR_DSE | PORT_PCR_MUX(1);
+	FTM0_MOD = 0xFFFF;
-	GPIOC_PCOR |= (1<<2);
+
-	GPIOC_PDDR |= (1<<3);
+	// Set FTM to PWM output - Edge Aligned, Low-true pulses
-	PORTC_PCR3 = PORT_PCR_SRE | PORT_PCR_DSE | PORT_PCR_MUX(1);
+	FTM0_C0SC = 0x24; // MSnB:MSnA = 10, ELSnB:ELSnA = 01
-	GPIOC_PCOR |= (1<<3);
+	FTM0_C1SC = 0x24;
+	FTM0_C2SC = 0x24;
+
+	// Base FTM clock selection (72 MHz system clock)
+	// Pre-scalar calculations
+	// 0 -      72 MHz - Highest power usage/best result
+	// 1 -      36 MHz
+	// 2 -      18 MHz
+	// 3 -       9 MHz - Slightly visible flicker (peripheral vision)
+	// 4 -   4 500 kHz - Visible flickering
+	// 5 -   2 250 kHz
+	// 6 -   1 125 kHz
+	// 7 - 562 500  Hz
+	// System clock, /w prescalar setting
+	FTM0_SC = FTM_SC_CLKS(1) | FTM_SC_PS( STLcdBacklightPrescalar_define );
+
+	/* Write frequency TODO API
+	FTM0_SC = 0;
+	FTM0_CNT = 0;
+	FTM0_MOD = mod;
+	FTM0_SC = FTM_SC_CLKS(1) | FTM_SC_PS(prescale);
+	*/
+
+	// Red
+	FTM0_C0V = STLcdBacklightRed_define;
+	PORTC_PCR1 = PORT_PCR_SRE | PORT_PCR_DSE | PORT_PCR_MUX(4);
+
+	// Green
+	FTM0_C1V = STLcdBacklightGreen_define;
+	PORTC_PCR2 = PORT_PCR_SRE | PORT_PCR_DSE | PORT_PCR_MUX(4);
+
+	// Blue
+	FTM0_C2V = STLcdBacklightBlue_define;
+	PORTC_PCR3 = PORT_PCR_SRE | PORT_PCR_DSE | PORT_PCR_MUX(4);
 }