knob: fix up brightness direction, limits

the knob now adjusts in a human-relatable way for min to max brightness.

the min and max brightness levels are now scaled correctly for the knob.

firmware/retro_tech_fw/user/src/adc.c

@@ -120,7 +120,7 @@ void adc_stop_lsens()
     GPIO_Init(GPIOA, &gpio);
 }
 
-uint16_t adc_get_pot()
+uint8_t adc_get_pot()
 {
     uint32_t pot;
 
@@ -135,7 +135,7 @@ uint16_t adc_get_pot()
     // 8 bits is good enough for us
     pot >>= 2;
 
-    return pot & 0xff;
+    return 255 - (pot & 0xff);
 }
 
 uint16_t adc_get_lsens()

firmware/retro_tech_fw/user/src/adc.h

@@ -20,7 +20,7 @@ void adc_read();
 void adc_use_lsens();
 void adc_reset_lsens();
 
-uint16_t adc_get_pot();
+uint8_t adc_get_pot();
 uint16_t adc_get_lsens();
 
 

firmware/retro_tech_fw/user/src/led.c

@@ -15,6 +15,25 @@
 static const uint8_t rgb_map[9] = {0x04, 0x14, 0x01, 0x11, 0x07, 0x0a, 0x1a, 0x0d, 0x1d};
 static const uint8_t cursor_map[3] = {0x17, 0x18, 0x19};
 
+static const uint8_t LED_CIE_PWM_256I_256O[] = {
+    0,    0,    0,    0,    0,    1,    1,    1,    1,    1,    1,    1,    1,    1,    2,    2,
+    2,    2,    2,    2,    2,    2,    2,    3,    3,    3,    3,    3,    3,    3,    3,    4,
+    4,    4,    4,    4,    4,    5,    5,    5,    5,    5,    6,    6,    6,    6,    6,    7,
+    7,    7,    7,    8,    8,    8,    8,    9,    9,    9,   10,   10,   10,   10,   11,   11,
+   11,   12,   12,   12,   13,   13,   13,   14,   14,   15,   15,   15,   16,   16,   17,   17,
+   17,   18,   18,   19,   19,   20,   20,   21,   21,   22,   22,   23,   23,   24,   24,   25,
+   25,   26,   26,   27,   28,   28,   29,   29,   30,   31,   31,   32,   32,   33,   34,   34,
+   35,   36,   37,   37,   38,   39,   39,   40,   41,   42,   43,   43,   44,   45,   46,   47,
+   47,   48,   49,   50,   51,   52,   53,   54,   54,   55,   56,   57,   58,   59,   60,   61,
+   62,   63,   64,   65,   66,   67,   68,   70,   71,   72,   73,   74,   75,   76,   77,   79,
+   80,   81,   82,   83,   85,   86,   87,   88,   90,   91,   92,   94,   95,   96,   98,   99,
+  100,  102,  103,  105,  106,  108,  109,  110,  112,  113,  115,  116,  118,  120,  121,  123,
+  124,  126,  128,  129,  131,  132,  134,  136,  138,  139,  141,  143,  145,  146,  148,  150,
+  152,  154,  155,  157,  159,  161,  163,  165,  167,  169,  171,  173,  175,  177,  179,  181,
+  183,  185,  187,  189,  191,  193,  196,  198,  200,  202,  204,  207,  209,  211,  214,  216,
+  218,  220,  223,  225,  228,  230,  232,  235,  237,  240,  242,  245,  247,  250,  252,  255,
+};
+
 
 
 uint16_t rgb[9][3] = {0};
@@ -66,3 +85,8 @@ void led_send()
         is31fl3729_set_outputs(FL3729_ADDR, 1, out, 16+15);
     }
 }
+
+uint8_t led_gamma(uint8_t in)
+{
+    return LED_CIE_PWM_256I_256O[in];
+}

firmware/retro_tech_fw/user/src/led.h

@@ -30,6 +30,8 @@ void led_init();
 void led_is_updated();
 void led_send();
 
+uint8_t led_gamma(uint8_t in);
+
 
 
 #endif /* USER_SRC_LED_H_ */

firmware/retro_tech_fw/user/src/ui.c

@@ -20,8 +20,8 @@
 #define MODE_PROGRAM            1
 #define MODE_PARAMETER          2
 
-#define MIN_GC                  4
+#define MIN_GC                  2
-#define MAX_GC                  60
+#define MAX_GC                  26
 
 #define UI_CONF_SAVE_TIMEOUT    160
 
@@ -324,7 +324,7 @@ static void ui_cursor_flash()
 
                 // set the level on the cursor
                 if (cursor[color] != level) {
-                    cursor[color] = level;
+                    cursor[color] = led_gamma(level);
                     led_is_updated();
                 }
 
@@ -376,10 +376,11 @@ void ui_init()
 
 void ui_render()
 {
+    uint8_t i;
+
+    uint16_t w;
     uint32_t t;
 
-    uint8_t i;
-    uint8_t w;
     uint8_t flash;
 
 
@@ -409,10 +410,17 @@ void ui_render()
         case MODE_RUN: {    // render an existing program
             tick++;
 
-            // set brightness from knob 64 times/second
+            // set brightness from knob 32 times/second
-            // (the value actually updates less frequently, but we need to fade nicely)
+            // (the knob value updates less frequently, but we need to fade nicely)
-            if (tick & 3 == 3) {
+            if (tick & 7 == 7) {
-                w = adc_get_pot() >> 2;
+                w = adc_get_pot();
+                if (w < 2) w = 0;
+                else {
+                    w *= MAX_GC - MIN_GC;
+                    w >>= 8;
+                    w += MIN_GC;
+                }
+
                 if (!w) {
                     if (target_gc) target_gc--;             // full off = full off.
                 } else if (w < target_gc) {