Started some tedious work on reverse engineering the correct functions for th RGB light outputs.

doc/RGB_mapping.py

@@ -0,0 +1,97 @@
+#!/usr/bin/env python3
+#
+# This script was used to work out how to map the RGB/brightness input
+# data to GPIO pinout voltages.
+
+maxV = 3.27
+
+requirements = [
+    # Input                # Expected output
+    (0, 0, 0, 1.00,        False, None, None, None),
+    (255, 255, 255, 0.00,  False, None, None, None),
+    (255, 0,   0, 0.01,    True, 2.95, maxV, maxV),
+    (255, 255, 0, 0.01,    True, 3.04, 2.86, 3.17),
+    (255, 255, 255, 0.01,  True, 3.04, 2.86, 3.07),
+    (0, 255, 0, 0.01,      True, 3.27, 2.95, 3.27),
+    (0, 255, 255, 0.01,    True, 3.13, 2.86, 3.07),
+    (0, 0, 255, 0.01,      True, 3.27, 3.27, 2.95),
+    (255, 0, 255, 0.01,    True, 2.88, 3.12, 2.86),
+]
+
+def get_red(r, g, b, brightness):
+    if r == 0:
+        if g == 1 and b == 1:
+            v = round(3.1317 - brightness * 0.16, 2)
+            return v
+        else:
+            return maxV; 
+    if g == 1:
+        v = round(r * (3.0417 - brightness * 0.48), 2)
+    elif b == 1:
+        v = round(r * (2.88 - (brightness - 0.01) * (2.88 - 1.85)), 2)
+    else:
+        v = round(r * (2.95 - (brightness - 0.01) * (2.95 - 1.82)), 2)
+        v = round(r * (2.9617 - brightness * 1.13), 2)
+    return v
+
+def get_green(r, g, b, brightness):
+    if g == 0:
+        if r == 1 and b == 1:
+            return round(3.12 - (brightness - 0.01) * (3.12 - 2.92), 2)
+        else:
+            return maxV; 
+    if r == 1:
+        v = round(g * (2.86 - (brightness - 0.01) * (2.86 - 1.77)), 2)
+    elif r == 0 and b == 1:
+        v = round(g * (2.86 - (brightness - 0.01) * (2.86 - 1.77)), 2)
+    else:
+        v = round(g * (2.95 - (brightness - 0.01) * (2.95 - 1.82)), 2)
+    return v
+
+def get_blue(r, g, b, brightness):
+    if b == 0:
+        if r > 0 and g > 0:
+            return 3.17
+        else:
+            return maxV; 
+    if r == 1 and g == 1:
+        v = round(r * (3.0717 - brightness * 0.48), 2)
+    elif r == 1 and g == 0:
+        v = round(r * (2.86 - (brightness - 0.01) * (2.86 - 1.77)), 2)
+    elif r == 0 and g == 1:
+        v = round(g * (3.0717 - brightness * 0.48), 2)
+    else:
+        v = round(b * (2.95 - (brightness - 0.01) * (2.95 - 1.82)), 2)
+    return v
+
+def make_rgb_fractions(r, g, b):
+    """ These ought to be 0 to 1 on input already, but it won't 
+        hurt to make sure they are."""
+    m = max(r, g, b)
+    r = r/m
+    g = g/m
+    b = b/m
+    return (r, g, b)
+
+
+for r,g,b,brightness,stateExpected, rVexpected, gVexpected, bVexpected in requirements:
+    print(f"IN: {r}, {g}, {b} at {brightness} / ", end="")
+    print(f"EXP: ({stateExpected}) {rVexpected},{gVexpected},{bVexpected} ", end="")
+
+    state = True
+    if r + g + b == 0 or brightness == 0:
+        state = False
+        rV = None
+        gV = None
+        bV = None
+    else:
+        r, g, b = make_rgb_fractions(r, g, b)
+        rV = get_red(r, g, b, brightness)
+        gV = get_green(r, g, b, brightness)
+        bV = get_blue(r, g, b, brightness)
+    print(f"OUT: ({state}) {rV},{gV},{bV} ", end="")
+    if rV == rVexpected and gV == gVexpected and bV == bVexpected and state == stateExpected:
+        print(" [PASS]");
+    else:
+        print(" [FAIL]");
+

yeelight_bs2.h

@@ -91,11 +91,6 @@ class YeelightBedsideLampV2LightOutput : public Component, public LightOutput
   {
     ESP_LOGD("custom", "Activate RGB %f, %f, %f, BRIGHTNESS %f", red, green, blue, brightness);
 
-    // This tunes the power for the red channel a bit, to bring
-    // the red=1, green=1, blue=1 color more towards white.
-    // (on my lamps, there is a faint hint of red in the color)
-    red = red * 0.93f;
-
     // Compensate for brightness.
     red = red * brightness;
     green = green * brightness;