Set up an initial sk9822 library

base/include/base.h

@@ -15,5 +15,15 @@ inline void clear_pin(io_pin_t *pin) {
     *(pin->port) &= 0xff ^ (1 << pin->pin);
 }
 
+typedef struct RNG {
+    uint8_t mod;
+    int8_t a;
+    int8_t c;
+    uint8_t seed;
+} rng_t;
+
+rng_t rng_new(uint8_t seed);
+
+uint8_t rng_sample(rng_t *state);
 
 #endif

base/src/base.c

@@ -0,0 +1,12 @@
+#include "../base.h"
+
+
+
+rng_t rng_new(uint8_t seed) {
+    return { .mod = 255, .a = 253, .c = 41, .seed = seed };
+}
+
+uint8_t rng_sample(rng_t *state) {
+    state->seed = (state->a * state->seed + state->c) % state->mod;
+    return state->seed;
+}

flake.nix

@@ -25,6 +25,7 @@
         };
         */
 
+        /*
       defaultPackage."x86_64-linux" =
         let
           pkgs = import nixpkgs { system = "x86_64-linux"; };
@@ -48,6 +49,7 @@
             cp main.elf main.hex $out
             '';
         };
+        */
 
       devShell."x86_64-linux" =
         let
@@ -55,12 +57,18 @@
           avr = with pkgs.pkgsCross.avr.buildPackages; [
             binutils
             gcc
+            gdb
             avrdude
+            simavr
+            gtkwave
           ];
         in
         pkgs.mkShell {
           name = "Wearables-shell";
           buildInputs = avr;
+
+          GCC="${pkgs.pkgsCross.avr.buildPackages.gcc}";
+          AVR="${pkgs.avrlibc}";
         };
     };
 }

sk9822/Makefile

@@ -0,0 +1,23 @@
+MCU=attiny85
+CHIP_SELECT=AVR_ATtiny85
+F_CPU=8000000
+CFLAGS=-O -finline-functions -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums -Wall -Wstrict-prototypes -DF_CPU=${F_CPU} -std=gnu99 -D__${CHIP_SELECT}__=1
+LINKFLAGS=-mmcu=${MCU}
+
+OBJECTS= main.o \
+		 sk9822.o
+
+.SUFFIXES: .c .o .h
+
+%.o: %.c %.h
+	${GCC}/bin/avr-gcc ${CFLAGS} ${AVR}/avr/include -I../base/include/ -o $@ -c $<
+
+main: main.o sk9822.o
+	# ${GCC}/bin/avr-gcc ${CFLAGS} -I../base/include/ -E -o main.E src/main.c
+	# ${GCC}/bin/avr-gcc ${CFLAGS} -I../base/include/ -S -o main.S src/main.c
+	${GCC}/bin/avr-gcc ${CFLAGS} ${LINKFLAGS} -I../base/include/ -o main.elf main.o sk9822.o
+	${OBJCOPY} -O ihex main.elf main.hex
+
+clean:
+	rm *.o make.elf main.hex main.S main.E
+

sk9822/main.c

@@ -0,0 +1,51 @@
+#include <avr/io.h>
+#include <util/delay.h>
+
+#include <base.h>
+#include "sk9822.h"
+
+uint8_t random_step(uint8_t value, uint8_t min, uint8_t max, rng_t *rng) {
+    int8_t step = (rng_sample(rng) % 32) - 16;
+    uint16_t new_value = value + step;
+    if (new_value > max) {
+       return max;
+    } else if (new_value < min) {
+        return min;
+    } else {
+        return new_value;
+    }
+}
+
+void flicker(rgb_t *pixel, rng_t *rng) {
+    pixel->r = random_step(pixel->r, 180, 255, rng);
+    pixel->g = random_step(pixel->g, 10, 40, rng);
+}
+
+int main (void) {
+    DDRB = _BV(2) | _BV(1) | _BV(0);
+    PORTB = 0;
+    _delay_ms(50);
+
+    io_pin_t data_pin = { .port = &PORTB, .pin = 0 };
+    io_pin_t clock_pin = { .port = &PORTB, .pin = 2 };
+
+    rgb_t lamps[2] = { { .brightness =  9, .r = 212, .g =  50, .b =   0 },
+                       { .brightness =  1, .r =   0, .g =   0, .b =   0 } };
+
+    int8_t step_1 = 1;
+    rng_t rng = rng_new(0);
+    while (1) {
+        send_pixels(data_pin, clock_pin, lamps, 2);
+
+        flicker(&lamps[0], &rng);
+
+        lamps[1].r += step_1;
+
+        if (lamps[1].r == 255) {
+            step_1 = -1;
+        } else if (lamps[1].r == 0) {
+            step_1 = 1;
+        }
+        _delay_ms(16);
+    }
+}

sk9822/sk9822.c

@@ -0,0 +1,36 @@
+void send_byte(io_pin_t data_pin, io_pin_t clock_pin, uint8_t byte) {
+    for (int i = 7; i >= 0; i--) {
+        if (byte & _BV(i)) {
+            (*data_pin.port) |= _BV(data_pin.pin);
+        } else {
+            (*data_pin.port) &= ~(_BV(data_pin.pin));
+        }
+        (*clock_pin.port) |= _BV(clock_pin.pin);
+        (*clock_pin.port) &= ~(_BV(clock_pin.pin));
+    }
+}
+
+void send_start(io_pin_t data_pin, io_pin_t clock_pin) {
+    send_byte(data_pin, clock_pin, 0);
+    send_byte(data_pin, clock_pin, 0);
+    send_byte(data_pin, clock_pin, 0);
+    send_byte(data_pin, clock_pin, 0);
+}
+
+void send_term(io_pin_t data_pin, io_pin_t clock_pin) {
+    send_byte(data_pin, clock_pin, 0xff);
+    send_byte(data_pin, clock_pin, 0xff);
+    send_byte(data_pin, clock_pin, 0xff);
+    send_byte(data_pin, clock_pin, 0xff);
+}
+
+void send_pixels(io_pin_t data_pin, io_pin_t clock_pin, rgb_t * pixels, uint8_t count) {
+    send_start(data_pin, clock_pin);
+    for (uint8_t i = 0; i < count; i++) {
+        send_byte(data_pin, clock_pin, 0xe0 + pixels[i].brightness);
+        send_byte(data_pin, clock_pin, pixels[i].r);
+        send_byte(data_pin, clock_pin, pixels[i].b);
+        send_byte(data_pin, clock_pin, pixels[i].g);
+    }
+    send_term(data_pin, clock_pin);
+}

sk9822/sk9822.h

@@ -0,0 +1,10 @@
+#include <avr/io.h>
+
+typedef struct RGB_s {
+    uint8_t brightness;
+    uint8_t r;
+    uint8_t g;
+    uint8_t b;
+} rgb_t;
+
+void send_pixels(io_pin_t data_pin, io_pin_t clock_pin, rgb_t *pixels, uint8_t count);