broke up main.c, optimized ISR, color channels can have different ports

Makefile

@@ -1,5 +1,5 @@
 # Default values
-OBJ            = main.o
+OBJ            = hw.o laborlicht.o main.o
 OUT           ?= image
 MCU_TARGET    ?= atmega8
 MCU_CC        ?= avr-gcc

config.h

@@ -0,0 +1,16 @@
+#ifndef CONFIG_H
+#define CONFIG_H
+
+#define DDR_RED  DDRC
+#define PORT_RED PORTC
+#define BIT_RED  PC0
+
+#define DDR_GREEN  DDRC
+#define PORT_GREEN PORTC
+#define BIT_GREEN  PC1
+
+#define DDR_BLUE  DDRC
+#define PORT_BLUE PORTC
+#define BIT_BLUE  PC2
+
+#endif // CONFIG_H

hw.c

@@ -0,0 +1,98 @@
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <avr/pgmspace.h>
+
+#include "config.h"
+#include "hw.h"
+
+volatile unsigned char g_color[channel_MAX] = {0};
+
+unsigned char const PROGMEM g_cie_table[256] = {
+     10,  11,  10,  11,  11,  10,  11,  11,
+     10,  11,  11,  10,  11,  11,  11,  10,
+     11,  11,  10,  11,  11,  10,  11,  12,
+     11,  13,  12,  13,  13,  14,  14,  14,
+     15,  16,  15,  17,  16,  17,  18,  18,
+     18,  19,  19,  20,  20,  21,  21,  22,
+     22,  23,  23,  24,  24,  25,  25,  26,
+     26,  27,  28,  28,  28,  30,  30,  30,
+     31,  31,  33,  32,  34,  34,  35,  35,
+     36,  36,  38,  37,  39,  39,  40,  41,
+     41,  42,  42,  44,  44,  44,  46,  46,
+     47,  47,  49,  49,  50,  50,  52,  52,
+     53,  54,  54,  55,  56,  57,  58,  58,
+     60,  60,  61,  62,  62,  64,  64,  65,
+     66,  67,  68,  69,  69,  71,  71,  73,
+     73,  74,  75,  76,  77,  78,  78,  80,
+     81,  81,  83,  84,  84,  86,  86,  88,
+     88,  90,  91,  91,  93,  93,  95,  96,
+     96,  98,  99, 100, 101, 102, 103, 105,
+    105, 106, 108, 108, 110, 111, 112, 113,
+    115, 115, 117, 117, 119, 120, 122, 122,
+    124, 124, 126, 127, 129, 129, 131, 132,
+    134, 134, 136, 137, 138, 140, 140, 142,
+    144, 144, 146, 147, 149, 150, 151, 152,
+    154, 155, 156, 158, 159, 160, 162, 163,
+    165, 166, 167, 168, 170, 172, 173, 174,
+    175, 177, 179, 180, 181, 183, 184, 186,
+    187, 189, 190, 191, 193, 195, 196, 197,
+    199, 201, 202, 203, 205, 207, 208, 209,
+    212, 212, 215, 216, 217, 219, 221, 222,
+    224, 225, 227, 229, 230, 232, 233, 236,
+    236, 239, 240, 241, 244, 245, 247, 248
+};
+
+ISR(TIMER_ISR) {
+    // duty cycle from 0 (0%) to 255 (100%)
+    static unsigned char duty_cycle = 0;
+
+    __asm__ volatile(
+        "cie_to_ocr2:"                          "\n\t"
+            "add r30,%[duty_cycle]; ZL"         "\n\t"
+            "adc r31,__zero_reg__ ; ZH"         "\n\t"
+            "lpm __tmp_reg__,Z"                 "\n\t"
+            xstr(OUT_STS) " %[ocr],__tmp_reg__" "\n\t"
+
+        "red_cmp:"                              "\n\t"
+            "lds __tmp_reg__,g_color"           "\n\t"
+            "cp __tmp_reg__,%[duty_cycle]"      "\n\t"
+            "brlo red_off"                      "\n\t"
+            "sbi %[port_red],%[bit_red]"        "\n\t"
+            "rjmp green_cmp"                    "\n\t"
+        "red_off:"                              "\n\t"
+            "cbi %[port_red],%[bit_red]"        "\n\t"
+
+        "green_cmp:"                            "\n\t"
+            "lds __tmp_reg__,g_color+1"         "\n\t"
+            "cp __tmp_reg__,%[duty_cycle]"      "\n\t"
+            "brlo green_off"                    "\n\t"
+            "sbi %[port_green],%[bit_green]"    "\n\t"
+            "rjmp blue_cmp"                     "\n\t"
+        "green_off:"                            "\n\t"
+            "cbi %[port_green],%[bit_green]"    "\n\t"
+
+        "blue_cmp:"                             "\n\t"
+            "lds __tmp_reg__,g_color+2"         "\n\t"
+            "cp __tmp_reg__,%[duty_cycle]"      "\n\t"
+            "brlo blue_off"                     "\n\t"
+            "sbi %[port_blue],%[bit_blue]"      "\n\t"
+            "rjmp finish"                       "\n\t"
+        "blue_off:"                             "\n\t"
+            "cbi %[port_blue],%[bit_blue]"      "\n\t"
+
+        "finish:"                               "\n\t"
+            "inc %[duty_cycle]"                 "\n\t"
+
+            : [duty_cycle] "+r" (duty_cycle)
+            : "[duty_cycle]" (duty_cycle),
+              "z" (&g_cie_table[0]) ,
+              [ocr]        "M" _SFR_IO_ADDR(OCR),
+              [port_red]   "M" _SFR_IO_ADDR(PORT_RED),
+              [port_green] "M" _SFR_IO_ADDR(PORT_GREEN),
+              [port_blue]  "M" _SFR_IO_ADDR(PORT_BLUE),
+              [bit_red]    "M" (BIT_RED),
+              [bit_green]  "M" (BIT_GREEN),
+              [bit_blue]   "M" (BIT_BLUE)
+    );
+}
+

hw.h

@@ -0,0 +1,124 @@
+#ifndef HW_H
+#define HW_H
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <avr/pgmspace.h>
+#include <stdlib.h>
+
+#include "config.h"
+
+#define xstr(s) str(s)
+#define str(s) #s
+
+#define PW(a) pgm_read_word(&(a))
+
+typedef enum color_channel_e {
+    channel_red,
+    channel_green,
+    channel_blue,
+    channel_MAX,
+} color_channel_t;
+
+extern volatile unsigned char g_color[channel_MAX];
+extern unsigned char const g_cie_table[256]; 
+
+// wait timer
+inline static void init_timer0(void) {
+#if defined(__AVR_ATmega8__) || \
+    defined(__AVR_ATmega8A__)
+#    define MY_TIFR TIFR
+    // clk/64
+    TCCR0 = _BV(CS01) | _BV(CS00);
+#elif defined(__AVR_ATmega48__)   || \
+      defined(__AVR_ATmega48P__)  || \
+      defined(__AVR_ATmega88__)   || \
+      defined(__AVR_ATmega88P__)  || \
+      defined(__AVR_ATmega168__)  || \
+      defined(__AVR_ATmega168P__) || \
+      defined(__AVR_ATmega328__)  || \
+      defined(__AVR_ATmega328P__)
+#    define MY_TIFR TIFR0
+    // clk/64
+    TCCR0B = _BV(CS01) | _BV(CS00);
+#else
+#    error MCU not supported
+#endif
+}
+
+// ISR timer
+inline static void init_timer2(void) {
+#if defined(__AVR_ATmega8__) || \
+    defined(__AVR_ATmega8A__)
+#    define TIMER_ISR TIMER2_COMP_vect
+#    define OUT_STS out
+#    define OCR OCR2
+    // CTC mode, OC2 disconnected, clk/8
+    TCCR2 = _BV(WGM21) | _BV(CS21);
+    // initialize compare match and counter registers
+    OCR2 = PW(g_cie_table[0]);
+    TCNT2 = 0;
+    // clear compare match flag and enable compare match interrupt handler
+    TIFR  |= _BV(OCF2);
+    TIMSK |= _BV(OCIE2);
+#elif defined(__AVR_ATmega48__)   || \
+      defined(__AVR_ATmega48P__)  || \
+      defined(__AVR_ATmega88__)   || \
+      defined(__AVR_ATmega88P__)  || \
+      defined(__AVR_ATmega168__)  || \
+      defined(__AVR_ATmega168P__) || \
+      defined(__AVR_ATmega328__)  || \
+      defined(__AVR_ATmega328P__)
+#    define TIMER_ISR TIMER2_COMPA_vect
+#    define OUT_STS sts
+#    define OCR OCR2A
+    // CTC mode, OC2A/OC2B disconnected, clk/8
+    TCCR2A = _BV(WGM21);
+    TCCR2B = _BV(CS21);
+    // initialize compare match and counter registers
+    OCR2A = PW(g_cie_table[0]);
+    TCNT2 = 0;
+    // clear compare match flag and enable compare match interrupt handler
+    TIFR2  |= _BV(OCF2A);
+    TIMSK2 |= _BV(OCIE2A);
+#else
+#    error MCU not supported
+#endif
+}
+
+inline static unsigned short get_seed()
+{
+    unsigned short seed = 0;
+    unsigned short *p = (unsigned short*) (RAMEND + 1);
+    extern unsigned short __heap_start;
+
+    while (p >= &__heap_start + 1)
+        seed ^= * (--p);
+
+    return seed;
+}
+
+// hardware initialization
+inline static void init_hw(void) {
+    srand(get_seed());
+
+    // set color pins to output mode
+    DDR_RED |= _BV(BIT_RED);
+    DDR_GREEN |= _BV(BIT_GREEN);
+    DDR_BLUE |= _BV(BIT_BLUE);
+
+    init_timer0();
+    init_timer2();
+    sei();
+}
+
+inline static void wait(unsigned int ms){
+    for (; ms--;) {
+        TCNT0 = 6;                      // overflow after 250 ticks, 1000 Hz
+        while (!(MY_TIFR & _BV(TOV0))); // wait for timer overflow flag
+        MY_TIFR = _BV(TOV0);            // reset overflow flag
+    }
+}
+
+#endif // HW_H
+

laborlicht.c

@@ -0,0 +1,44 @@
+#include <avr/pgmspace.h>
+
+#include "hw.h"
+#include "laborlicht.h"
+
+#define INTERIM_UPSCALE(a) ((a) * 128)
+#define INTERIM_DOWNSCALE(a) ((a) / 128)
+
+unsigned char const PROGMEM g_color_presets[color_MAX][channel_MAX] = {
+    {  0,   0,   0}, // black
+    {255,   0,   0}, // red
+    {255, 255,   0}, // yellow
+    {  0, 255,   0}, // green
+    {  0, 255, 255}, // teal
+    {  0,   0, 255}, // blue
+    {255,   0, 255}, // pink
+    {255, 255, 255}  // white
+};
+
+void color_fade(unsigned char const *fade_color,
+                unsigned char const steps,
+                unsigned int delay) {
+    int interim_color[channel_MAX];
+    int offset[channel_MAX];
+    for (color_channel_t channel = 0; channel < channel_MAX; ++channel) {
+        interim_color[channel] = INTERIM_UPSCALE(g_color[channel]);
+        offset[channel] =
+            INTERIM_UPSCALE(fade_color[channel] - g_color[channel]) / steps;
+    }
+
+    for (unsigned char step = 0; step < steps; ++step) {
+        for (color_channel_t channel = 0; channel < channel_MAX; ++channel) {
+            g_color[channel] =
+                INTERIM_DOWNSCALE(interim_color[channel] += offset[channel]);
+        }
+        wait(delay);
+    }
+
+    // counter measure against rounding errors
+    for (color_channel_t channel = 0; channel < channel_MAX; ++channel) {
+        g_color[channel] = fade_color[channel];
+    }
+}
+

laborlicht.h

@@ -0,0 +1,52 @@
+#ifndef LABORLICHT_H
+#define LABORLICHT_H
+
+#include <stdlib.h>
+
+#include "hw.h"
+
+typedef enum color_preset_e {
+    color_black,
+    color_red,
+    color_yellow,
+    color_green,
+    color_cyan,
+    color_blue,
+    color_purple,
+    color_white,
+    color_MAX
+} color_preset_t;
+
+extern unsigned char const g_color_presets[color_MAX][channel_MAX];
+
+inline static void set_color_preset(color_preset_t preset) {
+    g_color[channel_red]   = PW(g_color_presets[preset][channel_red]);
+    g_color[channel_green] = PW(g_color_presets[preset][channel_green]);
+    g_color[channel_blue]  = PW(g_color_presets[preset][channel_blue]);
+}
+
+void color_fade(unsigned char const *fade_color,
+                unsigned char const steps,
+                unsigned int delay);
+
+inline static void color_fade_preset(color_preset_t const preset,
+                                     unsigned char const steps,
+                                     unsigned int delay) {
+    unsigned char preset_color[channel_MAX];
+    for (unsigned char channel = 0; channel < channel_MAX; ++channel) {
+        preset_color[channel] = PW(g_color_presets[preset][channel]);
+    }
+    color_fade(preset_color, steps, delay);
+}
+
+// fade to a random color (minimum brightness per channel is 64);
+inline static void color_fade_random(unsigned char const steps,
+                                     unsigned int delay) {
+    unsigned char random_color[channel_MAX];
+    for (color_channel_t channel = 0; channel < channel_MAX; ++channel) {
+        random_color[channel] = (rand() % 192) + 64;
+    }
+    color_fade(random_color, steps, delay);
+}
+
+#endif // LABORLICHT_H