From 951b6f33a0dc479d29831aaa5c73fc526faf0471 Mon Sep 17 00:00:00 2001 From: Fred Sundvik Date: Sat, 1 Apr 2017 21:28:27 +0300 Subject: CIE 1931 for the LCD backlight --- keyboards/ergodox/infinity/infinity.c | 29 ++++++++++++++++++++++++++--- 1 file changed, 26 insertions(+), 3 deletions(-) (limited to 'keyboards/ergodox/infinity/infinity.c') diff --git a/keyboards/ergodox/infinity/infinity.c b/keyboards/ergodox/infinity/infinity.c index 02db67eaf..ecc072abb 100644 --- a/keyboards/ergodox/infinity/infinity.c +++ b/keyboards/ergodox/infinity/infinity.c @@ -70,10 +70,33 @@ void lcd_backlight_hal_init(void) { RGB_PORT->PCR[BLUE_PIN] = RGB_MODE; } +static uint16_t cie_lightness(uint16_t v) { + // The CIE 1931 formula for lightness + // Y = luminance (output) 0-1 + // L = lightness input 0 - 100 + + // Y = (L* / 902.3) if L* <= 8 + // Y = ((L* + 16) / 116)^3 if L* > 8 + + float l = 100.0f * (v / 65535.0f); + float y = 0.0f; + if (l <= 8.0f) { + y = l / 902.3; + } + else { + y = ((l + 16.0f) / 116.0f); + y = y * y * y; + if (y > 1.0f) { + y = 1.0f; + } + } + return y * 65535.0f; +} + 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; + CHANNEL_RED.CnV = cie_lightness(r); + CHANNEL_GREEN.CnV = cie_lightness(g); + CHANNEL_BLUE.CnV = cie_lightness(b); } __attribute__ ((weak)) -- cgit v1.2.3-70-g09d2