added new 8-line snake version with updated library copy

projects/lcdsnake_v2/Makefile

@@ -0,0 +1,167 @@
+
+MCU	= atmega328p
+
+F_CPU = 16000000
+
+LFUSE = 0xFF
+HFUSE = 0xDE
+EFUSE = 0x05
+
+MAIN = main.c
+
+## If you've split your program into multiple files,
+## include the additional .c source (in same directory) here
+## (and include the .h files in your foo.c)
+LOCAL_SOURCE =
+
+## Here you can link to one more directory (and multiple .c files)
+# EXTRA_SOURCE_DIR = ../AVR-Programming-Library/
+EXTRA_SOURCE_DIR = lib/
+EXTRA_SOURCE_FILES = debounce.c lcd.c adc.c
+
+EXTRA_CFLAGS  =
+
+##########------------------------------------------------------##########
+##########                 Programmer Defaults                  ##########
+##########          Set up once, then forget about it           ##########
+##########        (Can override.  See bottom of file.)          ##########
+##########------------------------------------------------------##########
+#19200
+PROGRAMMER_TYPE = arduino
+PROGRAMMER_ARGS = -b 57600 -P /dev/ttyUSB0
+
+
+##########------------------------------------------------------##########
+##########                   Makefile Magic!                    ##########
+##########         Summary:                                     ##########
+##########             We want a .hex file                      ##########
+##########        Compile source files into .elf                ##########
+##########        Convert .elf file into .hex                   ##########
+##########        You shouldn't need to edit below.             ##########
+##########------------------------------------------------------##########
+
+## Defined programs / locations
+CC = avr-gcc
+OBJCOPY = avr-objcopy
+OBJDUMP = avr-objdump
+AVRSIZE = avr-size
+AVRDUDE = avrdude
+
+## Compilation options, type man avr-gcc if you're curious.
+CFLAGS = -std=gnu99 -mmcu=$(MCU) -DF_CPU=$(F_CPU)UL -I. -I$(EXTRA_SOURCE_DIR)
+CFLAGS += -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums
+CFLAGS += -Wall -Wno-main -Wno-strict-prototypes -Wno-comment
+CFLAGS += -g2 -Wextra -Wfatal-errors
+CFLAGS += -ffunction-sections -fdata-sections -Wl,--gc-sections -Wl,--relax
+CFLAGS += $(EXTRA_CFLAGS)
+
+CFLAGS_BUILD = $(CFLAGS) -Os
+
+# CFLAGS += -lm
+## CFLAGS += -Wl,-u,vfprintf -lprintf_flt -lm  ## for floating-point printf
+## CFLAGS += -Wl,-u,vfprintf -lprintf_min      ## for smaller printf
+
+## Lump target and extra source files together
+TARGET = $(strip $(basename $(MAIN)))
+SRC1 = $(TARGET).c
+SRC = $(SRC1)
+EXTRA_SOURCE = $(addprefix $(EXTRA_SOURCE_DIR), $(EXTRA_SOURCE_FILES))
+SRC += $(EXTRA_SOURCE)
+SRC += $(LOCAL_SOURCE)
+
+## List of all header files
+HEADERS = $(SRC:.c=.h)
+
+## For every .c file, compile an .o object file
+OBJ = $(SRC:.c=.o)
+
+## Generic Makefile targets.  (Only .hex file is necessary)
+all: $(TARGET).hex size
+pre: $(TARGET).pre
+
+%.hex: %.elf
+	$(OBJCOPY) -R .eeprom -O ihex $< $@
+
+%.elf: $(SRC)
+	$(CC) $(CFLAGS_BUILD) $(SRC) --output $@
+
+%.pre: $(SRC1)
+	$(CC) $(CFLAGS) -E $(SRC1) --output $@
+
+%.eeprom: %.elf
+	$(OBJCOPY) -j .eeprom --change-section-lma .eeprom=0 -O ihex $< $@
+
+debug:
+	@echo
+	@echo "Source files:"   $(SRC)
+	@echo "MCU, F_CPU, BAUD:"  $(MCU), $(F_CPU), $(BAUD)
+	@echo
+
+# Optionally create listing file from .elf
+# This creates approximate assembly-language equivalent of your code.
+# Useful for debugging time-sensitive bits,
+# or making sure the compiler does what you want.
+disassemble: $(TARGET).lst
+
+dis: disassemble
+lst: disassemble
+
+eeprom: $(TARGET).eeprom
+
+%.lst: %.elf
+	$(OBJDUMP) -S $< > $@
+
+# Optionally show how big the resulting program is
+size:  $(TARGET).elf
+	$(AVRSIZE) -C --mcu=$(MCU) $(TARGET).elf
+
+clean:
+	rm -f $(TARGET).elf $(TARGET).hex $(TARGET).obj \
+	$(TARGET).o $(TARGET).d $(TARGET).eep $(TARGET).lst \
+	$(TARGET).lss $(TARGET).sym $(TARGET).map $(TARGET)~ \
+	$(TARGET).eeprom
+
+squeaky_clean:
+	rm -f *.elf *.hex *.obj *.o *.d *.eep *.lst *.lss *.sym *.map *~
+
+
+##########------------------------------------------------------##########
+##########              Programmer-specific details             ##########
+##########           Flashing code to AVR using avrdude         ##########
+##########------------------------------------------------------##########
+
+flash: $(TARGET).hex
+	$(AVRDUDE) -c $(PROGRAMMER_TYPE) -p $(MCU) $(PROGRAMMER_ARGS) -U flash:w:$<
+
+flash_eeprom: $(TARGET).eeprom
+	$(AVRDUDE) -c $(PROGRAMMER_TYPE) -p $(MCU) $(PROGRAMMER_ARGS) -U eeprom:w:$<
+
+terminal:
+	$(AVRDUDE) -c $(PROGRAMMER_TYPE) -p $(MCU) $(PROGRAMMER_ARGS) -nt
+
+
+flash_arduino: PROGRAMMER_TYPE = arduino
+flash_arduino: PROGRAMMER_ARGS =
+flash_arduino: flash
+
+flash_dragon_isp: PROGRAMMER_TYPE = dragon_isp
+flash_dragon_isp: PROGRAMMER_ARGS =
+flash_dragon_isp: flash
+
+
+##########------------------------------------------------------##########
+##########       Fuse settings and suitable defaults            ##########
+##########------------------------------------------------------##########
+
+## Generic
+FUSE_STRING = -U lfuse:w:$(LFUSE):m -U hfuse:w:$(HFUSE):m -U efuse:w:$(EFUSE):m
+
+fuses:
+	$(AVRDUDE) -c $(PROGRAMMER_TYPE) -p $(MCU) \
+	           $(PROGRAMMER_ARGS) $(FUSE_STRING)
+show_fuses:
+	$(AVRDUDE) -c $(PROGRAMMER_TYPE) -p $(MCU) $(PROGRAMMER_ARGS) -nv
+
+## Called with no extra definitions, sets to defaults
+set_default_fuses:  FUSE_STRING = -U lfuse:w:$(LFUSE):m -U hfuse:w:$(HFUSE):m -U efuse:w:$(EFUSE):m
+set_default_fuses:  fuses

projects/lcdsnake_v2/README.md

@@ -0,0 +1,10 @@
+Snake for HD44780
+=================
+
+This is a Snake game (known from old Nokia phones) played on a character display with HD44780.
+
+Program tested on Arduino Pro Mini (flashed with avrdude using the Makefile).
+
+**Connections** are `#define`d in `main.c`, board size and snake speed can also be adjusted. No external parts except the display and buttons required.
+
+Best works with a gamepad, but any buttons will work.

projects/lcdsnake_v2/debo_config.h

@@ -0,0 +1,5 @@
+#pragma once
+
+// Config file for debouncer
+#define DEBO_CHANNELS 6
+#define DEBO_TICKS 1

projects/lcdsnake_v2/lcd_config.h

@@ -0,0 +1,13 @@
+#pragma once
+
+// Config file for LCD.
+
+#include "lib/arduino_pins.h"
+
+#define LCD_RS D2
+#define LCD_RW D3
+#define LCD_E  D4
+#define LCD_D4 D5
+#define LCD_D5 D6
+#define LCD_D6 D7
+#define LCD_D7 D8

projects/lcdsnake_v2/lib/adc.c

@@ -0,0 +1,46 @@
+#include <avr/io.h>
+#include <stdbool.h>
+
+#include "calc.h"
+#include "adc.h"
+
+/** Initialize the ADC */
+void adc_init()
+{
+	ADCSRA |= _BV(ADPS2) | _BV(ADPS1) | _BV(ADPS0);  // 128 prescaler -> 125 kHz
+	ADMUX  |= _BV(REFS0);  // Voltage reference
+	sbi(ADCSRA, ADEN);  // Enable ADC
+}
+
+
+/** Disable AD */
+void adc_disable()
+{
+	cbi(ADCSRA, ADEN);
+}
+
+
+/** Sample analog pin with 8-bit precision */
+uint8_t adc_read_byte(uint8_t channel)
+{
+	write_low_nibble(ADMUX, channel);  // Select channel to sample
+	sbi(ADMUX, ADLAR);  // Align result to left
+	sbi(ADCSRA, ADSC);  // Start conversion
+
+	while(bit_is_high(ADCSRA, ADSC));  // Wait for it...
+
+	return ADCH;  // The upper 8 bits of ADC result
+}
+
+
+/** Sample analog pin with 10-bit precision */
+uint16_t adc_read_word(uint8_t channel)
+{
+	write_low_nibble(ADMUX, channel);  // Select channel to sample
+	cbi(ADMUX, ADLAR);  // Align result to right
+	sbi(ADCSRA, ADSC);  // Start conversion
+
+	while(get_bit(ADCSRA, ADSC));  // Wait for it...
+
+	return ADCW;  // The whole ADC word (10 bits)
+}

projects/lcdsnake_v2/lib/adc.h

@@ -0,0 +1,19 @@
+#pragma once
+
+//
+// Utilities for build-in A/D converter
+//
+
+#include <avr/io.h>
+
+/** Initialize the ADC */
+void adc_init();
+
+/** Disable AD (for power saving?) */
+void adc_disable();
+
+/** Sample analog pin with 8-bit precision */
+uint8_t adc_read_byte(uint8_t channel);
+
+/** Sample analog pin with 10-bit precision */
+uint16_t adc_read_word(uint8_t channel);

projects/lcdsnake_v2/lib/arduino_pins.h

@@ -0,0 +1,42 @@
+#pragma once
+
+//
+// Pin definitions for Arduino (Pro Mini with ATmega328P)
+//
+
+#include "pins.h"
+
+#define D0 D,0
+#define D1 D,1
+#define D2 D,2
+#define D3 D,3
+#define D4 D,4
+#define D5 D,5
+#define D6 D,6
+#define D7 D,7
+#define D8 B,0
+#define D9 B,1
+#define D10 B,2
+
+// MOSI MISO SCK - not good for input
+#define D11 B,3
+#define D12 B,4
+#define D13 B,5
+
+#define D14 C,0
+#define D15 C,1
+#define D16 C,2
+#define D17 C,3
+#define D18 C,4
+#define D19 C,5
+#define D20 C,6
+#define D21 C,7
+
+#define A0 C,0
+#define A1 C,1
+#define A2 C,2
+#define A3 C,3
+#define A4 C,4
+#define A5 C,5
+#define A6 C,6
+#define A7 C,7

projects/lcdsnake_v2/lib/calc.h

@@ -0,0 +1,91 @@
+#pragma once
+
+//
+// Bit and byte manipulation utilities
+//
+
+
+// --- Increment in range ---
+// when overflown, wraps within range. Lower bound < upper bound.
+// ..., upper bound excluded
+#define inc_wrap(var, min, max)  do { if ((var) >= (max - 1)) { (var) = (min); } else { (var)++; } } while(0)
+// ..., upper bound included
+#define inc_wrapi(var, min, max) inc_wrap((var), (min), (max) + 1)
+
+
+// --- Decrement in range ---
+// when underflown, wraps within range. Lower bound < upper bound.
+// ..., upper bound excluded
+#define dec_wrap(var, min, max)  do { if ((var) <= (min)) { (var) = (max) - 1; } else { (var)--; } } while(0)
+// ..., upper bound included
+#define dec_wrapi(var, min, max) dec_wrap((var), (min), (max) + 1)
+
+
+// --- Bit manipulation --
+
+// Set bit
+#define sbi(reg, bit) do { (reg) |=  (1 << (uint8_t)(bit)); } while(0)
+
+// Clear bit
+#define cbi(reg, bit) do { (reg) &= ~(1 << (uint8_t)(bit)); } while(0)
+
+// Get n-th bit
+#define read_bit(reg, bit) (((reg) >> (uint8_t)(bit)) & 0x1)
+#define get_bit(reg, bit)  read_bit(reg, bit)
+
+// Test n-th bit (Can't use bit_is_set, as it's redefined in sfr_def.h)
+#define bit_is_high(reg, bit) read_bit(reg, bit)
+#define bit_is_low(reg, bit)  (!read_bit(reg, bit))
+
+// Write value to n-th bit
+#define write_bit(reg, bit, value) do { (reg) = ((reg) & ~(1 << (uint8_t)(bit))) | (((uint8_t)(value) & 0x1) << (uint8_t)(bit)); } while(0)
+#define set_bit(reg, bit, value)   write_bit(reg, bit, value)
+
+// Invert n-th bit
+#define toggle_bit(reg, bit)       do { (reg) ^= (1 << (uint8_t)(bit)); } while(0)
+
+
+// --- Bit manipulation with pointer to variable ---
+
+// Set n-th bit in pointee
+#define sbi_p(reg_p, bit) do { (*(reg_p)) |=  (1 << (uint8_t)(bit)); } while(0)
+// Clear n-th bit in pointee
+#define cbi_p(reg_p, bit) do { (*(reg_p)) &= ~(1 << (uint8_t)(bit)); } while(0)
+
+// Get n-th bit in pointee
+#define read_bit_p(reg_p, bit) ((*(reg_p) >> (uint8_t)(bit)) & 0x1)
+#define get_bit_p(reg_p, bit)  read_bit_p(reg_p, bit)
+
+// Test n-th bit in pointee (Can't use bit_is_set, as it's redefined in sfr_def.h)
+#define bit_is_high_p(reg_p, bit) read_bit_p(reg_p, bit)
+#define bit_is_low_p(reg_p, bit)  (!read_bit_p(reg_p, bit))
+
+// Write value to a bit in pointee
+#define write_bit_p(reg_p, bit, value) do { *(reg_p) = (*(reg_p) & ~(1 << ((uint8_t)(bit) & 0x1))) | (((uint8_t)(value) & 0x1) << (uint8_t)(bit)); } while(0)
+#define set_bit_p(reg_p, bit, value)     write_bit_p(reg_p, bit, value)
+#define toggle_bit_p(reg_p, bit)       do { *(reg_p) ^= (1 << (uint8_t)(bit)); } while(0)
+
+
+// --- Nibble manipulation ---
+
+// Replace nibble in a byte
+#define write_low_nibble(reg, value)  do { (reg) = ((reg) & 0xF0) | ((uint8_t)(value) & 0xF); } while(0)
+#define write_high_nibble(reg, value) do { (reg) = ((reg) & 0x0F) | (((uint8_t)(value) & 0xF) << 4); } while(0)
+
+#define write_low_nibble_p(reg_p, value)  do { *(reg_p) = (*(reg_p) & 0xF0) | ((uint8_t)(value) & 0xF); } while(0)
+#define write_high_nibble_p(reg_p, value) do { *(reg_p) = (*(reg_p) & 0x0F) | (((uint8_t)(value) & 0xF) << 4); } while(0)
+
+#define low_nibble(x) ((uint8_t)(x) & 0xF)
+#define high_nibble(x) (((uint8_t)(x) & 0xF0) >> 4)
+
+// --- Range tests ---
+
+// Test if X is within low..high, regardless of bounds order
+#define in_range(x, low, high)  ((((low)  < (high)) && ((x) >= (low) && (x)  < (high))) || (((low) > (high)) && ((x) >= (high) && (x)  < (low))))
+// ..., include greater bound
+#define in_rangei(x, low, high) ((((low) <= (high)) && ((x) >= (low) && (x) <= (high))) || (((low) > (high)) && ((x) >= (high) && (x) <= (low))))
+
+// Test if X in low..high, wrap around ends if needed.
+#define in_range_wrap(x, low, high)  ((((low)  < (high)) && ((x) >= (low) && (x) < (high)))  || (((low) > (high)) && ((x) >= (low) || (x)  < (high))))
+// ..., include upper bound
+#define in_range_wrapi(x, low, high) ((((low) <= (high)) && ((x) >= (low) && (x) <= (high))) || (((low) > (high)) && ((x) >= (low) || (x) <= (high))))

projects/lcdsnake_v2/lib/debounce.c

@@ -0,0 +1,45 @@
+#include <avr/io.h>
+#include <stdbool.h>
+
+#include "debounce.h"
+#include "calc.h"
+#include "pins.h"
+#include "debo_config.h"
+
+/** Debounce data array */
+uint8_t debo_next_slot = 0;
+
+uint8_t debo_register(PORT_P reg, uint8_t bit, bool invert)
+{
+	debo_slots[debo_next_slot] = (debo_slot_t){
+		.reg = reg,
+		.bit = bit | ((invert & 1) << 7) | (get_bit_p(reg, bit) << 6), // bit 7 = invert, bit 6 = state
+		.count = 0,
+	};
+
+	return debo_next_slot++;
+}
+
+
+/** Check debounced pins, should be called periodically. */
+void debo_tick()
+{
+	for (uint8_t i = 0; i < debo_next_slot; i++) {
+		// current pin value (right 3 bits, xored with inverse bit)
+		bool value = get_bit_p(debo_slots[i].reg, debo_slots[i].bit & 0x7);
+
+		if (value != get_bit(debo_slots[i].bit, 6)) {
+
+			// different pin state than last recorded state
+			if (debo_slots[i].count < DEBO_TICKS) {
+				debo_slots[i].count++;
+			} else {
+				// overflown -> latch value
+				set_bit(debo_slots[i].bit, 6, value); // set state bit
+				debo_slots[i].count = 0;
+			}
+		} else {
+			debo_slots[i].count = 0; // reset the counter
+		}
+	}
+}

projects/lcdsnake_v2/lib/debounce.h

@@ -0,0 +1,64 @@
+#pragma once
+
+//
+//  An implementation of button debouncer.
+//
+//  ----
+//
+//  You must provide a config file debo_config.h (next to your main.c)
+//
+//  Example:
+//    #pragma once
+//    #define DEBO_CHANNELS 2
+//    #define DDEBO_TICKS 5
+//
+//  ----
+//
+//  A pin is registered like this:
+//
+//    #define BTN1 B,0
+//    #define BTN2 B,1
+//
+//    debo_add(BTN0);  // The function returns number assigned to the pin (0, 1, ...)
+//    debo_add_rev(BTN1);  // active low
+//    debo_register(&PINB, PB2, 0);  // direct access - register, pin & invert
+//
+//  Then periodically call the tick function (perhaps in a timer interrupt):
+//
+//    debo_tick();
+//
+//  To check if input is active, use
+//
+//    debo_get_pin(0); // state of input #0 (registered first)
+//    debo_get_pin(1); // state of input #1 (registered second)
+//
+
+
+#include <avr/io.h>
+#include <stdbool.h>
+
+#include "calc.h"
+#include "pins.h"
+#include "debo_config.h"
+
+/* Internal deboucer entry */
+typedef struct {
+	PORT_P reg;    // pointer to IO register
+	uint8_t bit;   // bits 6 and 7 of this hold "state" & "invert" flag
+	uint8_t count; // number of ticks this was in the new state
+} debo_slot_t;
+
+debo_slot_t debo_slots[DEBO_CHANNELS];
+
+/** Add a pin for debouncing */
+#define debo_add_rev(io) debo_register(&io2pin(io_pack(io)), io2n(io_pack(io)), 1)
+#define debo_add(io)  debo_register(&io2pin(io_pack(io)), io2n(io_pack(io)), 0)
+
+/** Add a pin for debouncing (low level function) */
+uint8_t debo_register(PORT_P pin_reg_pointer, uint8_t bit, bool invert);
+
+/** Check debounced pins, should be called periodically. */
+void debo_tick();
+
+/** Get a value of debounced pin */
+#define debo_get_pin(i) (get_bit(debo_slots[i].bit, 6) ^ get_bit(debo_slots[i].bit, 7))

projects/lcdsnake_v2/lib/lcd.c

@@ -0,0 +1,358 @@
+#include <stdbool.h>
+#include <stdint.h>
+#include <avr/io.h>
+#include <avr/pgmspace.h>
+#include <util/delay.h>
+
+#include "calc.h"
+#include "pins.h"
+#include "nsdelay.h"
+#include "lcd.h"
+#include "lcd_config.h"
+
+// Start address of rows
+const uint8_t LCD_ROW_ADDR[] = {0x00, 0x40, 0x14, 0x54};
+
+
+// Shared stream instance
+static STREAM _lcd_singleton;
+STREAM* lcd;
+
+
+// Internal prototypes
+void _lcd_mode_r();
+void _lcd_mode_w();
+void _lcd_clk();
+void _lcd_wait_bf();
+void _lcd_write_byte(uint8_t bb);
+uint8_t _lcd_read_byte();
+
+
+// Write utilities
+#define _lcd_write_low(bb)  _lcd_write_nibble((bb) & 0x0F)
+#define _lcd_write_high(bb) _lcd_write_nibble(((bb) & 0xF0) >> 4)
+#define _lcd_write_nibble(nib) do {                \
+	write_pin(LCD_D7, get_bit((nib), 3));     \
+	write_pin(LCD_D6, get_bit((nib), 2));     \
+	write_pin(LCD_D5, get_bit((nib), 1));     \
+	write_pin(LCD_D4, get_bit((nib), 0));     \
+} while(0)
+
+
+// 0 W, 1 R
+bool _lcd_mode;
+
+struct {
+	uint8_t x;
+	uint8_t y;
+} _pos;
+
+enum {
+	TEXT = 0,
+	CG = 1
+} _addrtype;
+
+
+/** Initialize the display */
+void lcd_init()
+{
+	// configure pins as output
+	as_output(LCD_E);
+	as_output(LCD_RW);
+	as_output(LCD_RS);
+	_lcd_mode = 1;  // force data pins to output
+	_lcd_mode_w();
+
+	// Magic sequence to invoke Cthulhu (or enter 4-bit mode)
+	_delay_ms(16);
+	_lcd_write_nibble(0b0011);
+	_lcd_clk();
+	_delay_ms(5);
+	_lcd_clk();
+	_delay_ms(5);
+	_lcd_clk();
+	_delay_ms(5);
+	_lcd_write_nibble(0b0010);
+	_lcd_clk();
+	_delay_us(100);
+
+	// Configure the display
+	lcd_command(LCD_IFACE_4BIT_2LINE);
+	lcd_command(LCD_DISABLE);
+	lcd_command(LCD_CLEAR);
+	lcd_command(LCD_MODE_INC);
+
+	// mark as enabled
+	lcd_enable();
+
+	_lcd_singleton.tx = &lcd_write;
+	_lcd_singleton.rx = &lcd_read;
+
+	// Stream
+	lcd = &_lcd_singleton;
+
+	_pos.x = 0;
+	_pos.y = 0;
+	_addrtype = TEXT;
+}
+
+
+/** Send a pulse on the ENABLE line */
+void _lcd_clk()
+{
+	pin_up(LCD_E);
+	delay_ns(450);
+	pin_down(LCD_E);
+}
+
+
+/** Enter READ mode */
+void _lcd_mode_r()
+{
+	if (_lcd_mode == 1) return;  // already in R mode
+
+	pin_up(LCD_RW);
+
+	as_input_pu(LCD_D7);
+	as_input_pu(LCD_D6);
+	as_input_pu(LCD_D5);
+	as_input_pu(LCD_D4);
+
+	_lcd_mode = 1;
+}
+
+
+/** Enter WRITE mode */
+void _lcd_mode_w()
+{
+	if (_lcd_mode == 0) return;  // already in W mode
+
+	pin_down(LCD_RW);
+
+	as_output(LCD_D7);
+	as_output(LCD_D6);
+	as_output(LCD_D5);
+	as_output(LCD_D4);
+
+	_lcd_mode = 0;
+}
+
+
+/** Read a byte */
+uint8_t _lcd_read_byte()
+{
+	_lcd_mode_r();
+
+	uint8_t res = 0;
+
+	_lcd_clk();
+	res = (read_pin(LCD_D7) << 7) | (read_pin(LCD_D6) << 6) | (read_pin(LCD_D5) << 5) | (read_pin(LCD_D4) << 4);
+
+	_lcd_clk();
+	res |= (read_pin(LCD_D7) << 3) | (read_pin(LCD_D6) << 2) | (read_pin(LCD_D5) << 1) | (read_pin(LCD_D4) << 0);
+
+	return res;
+}
+
+
+/** Write an instruction byte */
+void lcd_command(uint8_t bb)
+{
+	_lcd_wait_bf();
+	pin_down(LCD_RS);  // select instruction register
+	_lcd_write_byte(bb);    // send instruction byte
+}
+
+
+/** Write a data byte */
+void lcd_write(uint8_t bb)
+{
+	if (_addrtype == TEXT) {
+		if (bb == '\r') {
+			// CR
+			_pos.x = 0;
+			lcd_xy(_pos.x, _pos.y);
+			return;
+		}
+
+		if (bb == '\n') {
+			// LF
+			_pos.y++;
+			lcd_xy(_pos.x, _pos.y);
+			return;
+		}
+
+		_pos.x++;
+	}
+
+	_lcd_wait_bf();
+	pin_up(LCD_RS);  // select data register
+	_lcd_write_byte(bb);  // send data byte
+}
+
+
+/** Read BF & Address */
+uint8_t lcd_read_bf_addr()
+{
+	pin_down(LCD_RS);
+	return _lcd_read_byte();
+}
+
+
+/** Read CGRAM or DDRAM */
+uint8_t lcd_read()
+{
+	if (_addrtype == TEXT) _pos.x++;
+
+	pin_up(LCD_RS);
+	return _lcd_read_byte();
+}
+
+
+/** Write a byte using the 4-bit interface */
+void _lcd_write_byte(uint8_t bb)
+{
+	_lcd_mode_w();  // enter W mode
+
+	_lcd_write_high(bb);
+	_lcd_clk();
+
+	_lcd_write_low(bb);
+	_lcd_clk();
+}
+
+
+
+/** Wait until the device is ready */
+void _lcd_wait_bf()
+{
+	uint8_t d = 0;
+	while(d++ < 120 && lcd_read_bf_addr() & _BV(7))
+		_delay_us(1);
+}
+
+
+/** Send a string to LCD */
+void lcd_puts(char* str_p)
+{
+	char c;
+	while ((c = *str_p++))
+		lcd_putc(c);
+}
+
+
+/** Print from progmem */
+void lcd_puts_P(const char* str_p)
+{
+	char c;
+	while ((c = pgm_read_byte(str_p++)))
+		lcd_putc(c);
+}
+
+
+/** Sedn a char to LCD */
+void lcd_putc(const char c)
+{
+	lcd_write(c);
+}
+
+
+/** Set cursor position */
+void lcd_xy(const uint8_t x, const uint8_t y)
+{
+	_pos.x = x;
+	_pos.y = y;
+	lcd_addr(LCD_ROW_ADDR[y] + (x));
+}
+
+
+uint8_t _lcd_old_cursor = CURSOR_NONE;
+bool _lcd_enabled = false;
+
+/** Set LCD cursor. If not enabled, only remember it. */
+void lcd_cursor(uint8_t type)
+{
+	_lcd_old_cursor = (type & CURSOR_BOTH);
+
+	if (_lcd_enabled) lcd_command(LCD_CURSOR_NONE | _lcd_old_cursor);
+}
+
+
+/** Display display (preserving cursor) */
+void lcd_disable()
+{
+	lcd_command(LCD_DISABLE);
+	_lcd_enabled = false;
+}
+
+
+/** Enable display (restoring cursor) */
+void lcd_enable()
+{
+	_lcd_enabled = true;
+	lcd_cursor(_lcd_old_cursor);
+}
+
+
+/** Go home */
+void lcd_home()
+{
+	lcd_command(LCD_HOME);
+	_pos.x = 0;
+	_pos.y = 0;
+	_addrtype = TEXT;
+}
+
+
+/** Clear the screen */
+void lcd_clear()
+{
+	lcd_command(LCD_CLEAR);
+	_pos.x = 0;
+	_pos.y = 0;
+	_addrtype = TEXT;
+}
+
+
+/** Define a glyph */
+void lcd_glyph(const uint8_t index, const uint8_t* array)
+{
+	lcd_addr_cg(index * 8);
+	for (uint8_t i = 0; i < 8; ++i)	{
+		lcd_write(array[i]);
+	}
+
+	// restore previous position
+	lcd_xy(_pos.x, _pos.y);
+	_addrtype = TEXT;
+}
+
+
+/** Define a glyph */
+void lcd_glyph_P(const uint8_t index, const uint8_t* array)
+{
+	lcd_addr_cg(index * 8);
+	for (uint8_t i = 0; i < 8; ++i)	{
+		lcd_write(pgm_read_byte(&array[i]));
+	}
+
+	// restore previous position
+	lcd_xy(_pos.x, _pos.y);
+	_addrtype = TEXT;
+}
+
+
+/** Set address in CGRAM */
+void lcd_addr_cg(const uint8_t acg)
+{
+	_addrtype = CG;
+	lcd_command(0b01000000 | ((acg) & 0b00111111));
+}
+
+
+/** Set address in DDRAM */
+void lcd_addr(const uint8_t add)
+{
+	_addrtype = TEXT;
+	lcd_command(0b10000000 | ((add) & 0b01111111));
+}

projects/lcdsnake_v2/lib/lcd.h

@@ -0,0 +1,146 @@
+#pragma once
+
+//  HD44780 LCD display driver - 4-bit mode
+//
+//  LCD pins are configured using a file lcd_config.h, which you
+//  have to add next to your main.c file.
+//
+//  Content can be something like this:
+//
+//    #pragma once
+//    #include "lib/arduino_pins.h"
+//    #define LCD_RS D10
+//    #define LCD_RW D11
+//    #define LCD_E  D12
+//    #define LCD_D4 D13
+//    #define LCD_D5 D14
+//    #define LCD_D6 D15
+//    #define LCD_D7 D16
+//
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#include "stream.h"
+
+// File with configs
+#include "lcd_config.h"
+
+
+
+// Shared LCD stream object
+// Can be used with functions from stream.h once LCD is initialized
+extern STREAM* lcd;
+
+
+// --- Commands ---
+
+// Clear screen (reset)
+#define LCD_CLEAR 0b00000001
+// Move cursor to (0,0), unshift...
+#define LCD_HOME  0b00000010
+
+// Set mode: Increment + NoShift
+#define LCD_MODE_INC         0b00000110
+// Set mode: Increment + Shift
+#define LCD_MODE_INC_SHIFT   0b00000111
+
+// Set mode: Decrement + NoShift
+#define LCD_MODE_DEC         0b00000100
+// Set mode: Decrement + Shift
+#define LCD_MODE_DEC_SHIFT   0b00000101
+
+// Disable display (data remains untouched)
+#define LCD_DISABLE          0b00001000
+
+// Disable cursor
+#define LCD_CURSOR_NONE      0b00001100
+// Set cursor to still underscore
+#define LCD_CURSOR_BAR       0b00001110
+// Set cursor to blinking block
+#define LCD_CURSOR_BLINK     0b00001101
+// Set cursor to both of the above at once
+#define LCD_CURSOR_BOTH      (LCD_CURSOR_BAR | LCD_CURSOR_BLINK)
+
+// Move cursor
+#define LCD_MOVE_LEFT  0b00010000
+#define LCD_MOVE_RIGHT 0b00010100
+
+// Shift display
+#define LCD_SHIFT_LEFT  0b00011000
+#define LCD_SHIFT_RIGHT 0b00011100
+
+// Set iface to 5x7 font, 1-line
+#define LCD_IFACE_4BIT_1LINE 0b00100000
+#define LCD_IFACE_8BIT_1LINE 0b00110000
+// Set iface to 5x7 font, 2-line
+#define LCD_IFACE_4BIT_2LINE 0b00101000
+#define LCD_IFACE_8BIT_2LINE 0b00111000
+
+
+/** Initialize the display */
+void lcd_init();
+
+/** Write an instruction byte */
+void lcd_command(uint8_t bb);
+
+/** Write a data byte */
+void lcd_write(uint8_t bb);
+
+/** Read BF & Address */
+uint8_t lcd_read_bf_addr();
+
+/** Read CGRAM or DDRAM */
+uint8_t lcd_read();
+
+/** Send a string to LCD */
+void lcd_puts(char* str_p);
+
+/** Send a string to LCD from program memory */
+void lcd_puts_P(const char* str_p);
+
+/** Sedn a char to LCD */
+void lcd_putc(const char c);
+
+/** Show string at X, Y */
+#define lcd_puts_xy(x, y, str_p) do { lcd_xy((x), (y)); lcd_puts((str_p)); } while(0)
+
+/** Show string at X, Y */
+#define lcd_puts_xy_P(x, y, str_p) do { lcd_xy((x), (y)); lcd_puts_P((str_p)); } while(0)
+
+/** Show char at X, Y */
+#define lcd_putc_xy(x, y, c) do { lcd_xy((x), (y)); lcd_putc((c)); } while(0)
+
+/** Set cursor position */
+void lcd_xy(const uint8_t x, const uint8_t y);
+
+/** Set LCD cursor. If not enabled, only remember it. */
+#define CURSOR_NONE  0b00
+#define CURSOR_BAR   0b10
+#define CURSOR_BLINK 0b01
+#define CURSOR_BOTH  0b11
+void lcd_cursor(uint8_t type);
+
+/** Display display (preserving cursor) */
+void lcd_disable();
+
+/** Enable display (restoring cursor) */
+void lcd_enable();
+
+/** Go home */
+void lcd_home();
+
+/** Clear the screen */
+void lcd_clear();
+
+/** Define a glyph - 8 bytes, right 5 bits are used */
+void lcd_glyph(const uint8_t index, const uint8_t* array);
+
+/** Define a glyph that's in PROGMEM */
+void lcd_glyph_P(const uint8_t index, const uint8_t* array);
+
+/** Set address in CGRAM */
+void lcd_addr_cg(const uint8_t acg);
+
+/** Set address in DDRAM */
+void lcd_addr(const uint8_t add);

projects/lcdsnake_v2/lib/meta.h

@@ -0,0 +1,6 @@
+#pragma once
+
+// Weird constructs for the compiler
+
+// general macros
+#define SECTION(pos) __attribute__((naked, used, section(pos)))

projects/lcdsnake_v2/lib/nsdelay.h

@@ -0,0 +1,21 @@
+#pragma once
+
+//
+// Functions for precise delays (nanoseconds / cycles)
+//
+
+#include <avr/io.h>
+#include <util/delay_basic.h>
+#include <stdint.h>
+
+/* Convert nanoseconds to cycle count */
+#define ns2cycles(ns)  ( (ns) / (1000000000L / (signed long) F_CPU) )
+
+/** Wait c cycles */
+#define delay_c(c)  (((c) > 0) ? __builtin_avr_delay_cycles(c) :  __builtin_avr_delay_cycles(0))
+
+/** Wait n nanoseconds, plus c cycles  */
+#define delay_ns_c(ns, c)  delay_c(ns2cycles(ns) + (c))
+
+/** Wait n nanoseconds  */
+#define delay_ns(ns)  delay_c(ns2cycles(ns))

projects/lcdsnake_v2/lib/pins.h

@@ -0,0 +1,129 @@
+#pragma once
+
+//
+//  This file provides macros for pin manipulation.
+//
+//  You can define your application pins like so:
+//
+//      // Led at PORTB, pin 1
+//      #define LED B,1
+//
+//      // Switch at PORTD, pin 7
+//      #define SW1 D,7
+//
+//  Now you can use macros from this file to wirh with the pins, eg:
+//
+//      as_output(LED);
+//      as_input(SW1);
+//      pullup_on(SW1);
+//
+//      toggle_pin(LED);
+//      while (pin_is_low(SW1));
+//
+//  - The macros io2XXX() can be used to get literal name of register associated with the pin.
+//  - io2n() provides pin number.
+//  - The underscored and _aux macros are internal and should not be used elsewhere.
+//  - The io_pack() macro is used to pass pin (io) to other macro without expanding it.
+//
+
+#include <avr/io.h>
+#include "calc.h"
+
+// Helpers
+// Get particular register associated with the name X (eg. D -> PORTD)
+#define _reg_ddr(X) DDR ## X
+#define _reg_port(X) PORT ## X
+#define _reg_pin(X) PIN ## X
+#define _io2ddr_aux(reg, bit) _reg_ddr(reg)
+#define _io2port_aux(reg, bit) _reg_port(reg)
+#define _io2pin_aux(reg, bit) _reg_pin(reg)
+#define _io2n_aux(reg, bit) bit
+
+
+// === Convert A,1 to corresponding register and pin number ===
+
+#define io2ddr(io) _io2ddr_aux(io)
+#define io2port(io) _io2port_aux(io)
+#define io2pin(io) _io2pin_aux(io)
+#define io2n(io) _io2n_aux(io)
+
+// === covert "A", "1" to "A,1" for passing on to another macro ===
+#define io_pack(port, bit) port, bit
+
+
+// === Useful types for ports and pins ===
+
+// pointer to port
+typedef volatile uint8_t* PORT_P;
+// number of bit in port
+typedef uint8_t BIT_N;
+
+
+// === pin manipulation ===
+
+// Helpers
+#define _set_pin_aux(port, bit) sbi(_reg_port(port), (bit))
+#define _clear_pin_aux(port, bit) cbi(_reg_port(port), (bit))
+#define _read_pin_aux(port, bit) get_bit(_reg_pin(port), (bit))
+#define _write_pin_aux(port, bit, value) set_bit(_reg_port(port), (bit), (value))
+#define _toggle_pin_aux(port, bit) sbi(_reg_pin(port), (bit))
+
+
+// Set pin to HIGH
+#define pin_up(io) _set_pin_aux(io)
+#define pin_high(io) _set_pin_aux(io)
+
+// Set pin to LOW
+#define pin_down(io) _clear_pin_aux(io)
+#define pin_low(io) _clear_pin_aux(io)
+
+// Get input pin value
+#define get_pin(io) _read_pin_aux(io)
+#define read_pin(io) _read_pin_aux(io)
+
+// Check if pin is low or high
+#define pin_is_low(io) !_read_pin_aux(io)
+#define pin_is_high(io) _read_pin_aux(io)
+
+// Write a value to pin
+#define set_pin(io, value) _write_pin_aux(io, (value))
+#define write_pin(io, value) _write_pin_aux(io, (value))
+#define toggle_pin(io) _toggle_pin_aux(io)
+
+
+// === Setting pin direction ===
+
+// Helpers
+#define _as_input_aux(port, bit) cbi(_reg_ddr(port), (bit))
+#define _as_output_aux(port, bit) sbi(_reg_ddr(port), (bit))
+#define _set_dir_aux(port, bit, dir) write_bit(_reg_ddr(port), (bit), (dir))
+
+
+// Pin as input (_pu ... with pull-up)
+#define as_input(io) _as_input_aux(io)
+#define as_input_pu(io) do { _as_input_aux(io); _pullup_enable_aux(io); } while(0)
+
+// Pin as output
+#define as_output(io) _as_output_aux(io)
+
+// Set direction (1 ... output)
+#define set_dir(io, dir) _set_dir_aux(io, (dir))
+
+
+// === Setting pullup ===
+
+// Helpers
+#define _pullup_enable_aux(port, bit) sbi(_reg_port(port), (bit))
+#define _pullup_disable_aux(port, bit) cbi(_reg_port(port), (bit))
+#define _set_pullup_aux(port, bit, on) write_bit(_reg_port(port), (bit), (on))
+
+// Enable pullup
+#define pullup_enable(io) _pullup_enable_aux(io)
+#define pullup_on(io) _pullup_enable_aux(io)
+
+// Disable pullup
+#define pullup_disable(io) _pullup_disable_aux(io)
+#define pullup_off(io) _pullup_disable_aux(io)
+
+// Set pullup to value (1 ... pullup enabled)
+#define set_pullup(io, on) _set_pullup_aux(io, on)

projects/lcdsnake_v2/lib/stream.c

@@ -0,0 +1,211 @@
+#include <stdlib.h>
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "stream.h"
+#include "calc.h"
+
+
+static char tmpstr[20]; // buffer for number rendering
+
+
+void put_str(const STREAM *p, char* str)
+{
+	char c;
+	while ((c = *str++))
+		p->tx(c);
+}
+
+
+void put_str_P(const STREAM *p, const char* str)
+{
+	char c;
+	while ((c = pgm_read_byte(str++)))
+		p->tx(c);
+}
+
+
+static void _putnf(const STREAM *p, const uint8_t places);
+
+
+/** Send signed int8 */
+void put_u8(const STREAM *p, const uint8_t num)
+{
+	utoa(num, tmpstr, 10);
+	put_str(p, tmpstr);
+}
+
+
+/** Send unsigned int8 */
+void put_i8(const STREAM *p, const int8_t num)
+{
+	itoa(num, tmpstr, 10);
+	put_str(p, tmpstr);
+}
+
+
+
+/** Send unsigned int */
+void put_u16(const STREAM *p, const uint16_t num)
+{
+	utoa(num, tmpstr, 10);
+	put_str(p, tmpstr);
+}
+
+
+/** Send signed int */
+void put_i16(const STREAM *p, const int16_t num)
+{
+	itoa(num, tmpstr, 10);
+	put_str(p, tmpstr);
+}
+
+
+/** Send unsigned long */
+void put_u32(const STREAM *p, const uint32_t num)
+{
+	ultoa(num, tmpstr, 10);
+	put_str(p, tmpstr);
+}
+
+
+/** Send signed long */
+void put_i32(const STREAM *p, const int32_t num)
+{
+	ltoa(num, tmpstr, 10);
+	put_str(p, tmpstr);
+}
+
+
+/** Print number as hex */
+void _print_hex(const STREAM *p, uint8_t* start, uint8_t bytes)
+{
+	for (; bytes > 0; bytes--) {
+		uint8_t b = *(start + bytes - 1);
+
+		for(uint8_t j = 0; j < 2; j++) {
+			uint8_t x = high_nibble(b);
+			b = b << 4;
+			if (x < 0xA) {
+				p->tx('0' + x);
+			} else {
+				p->tx('A' + (x - 0xA));
+			}
+		}
+	}
+}
+
+
+/** Send unsigned int8 */
+void put_x8(const STREAM *p, const uint8_t num)
+{
+	_print_hex(p, (uint8_t*) &num, 1);
+}
+
+
+/** Send int as hex */
+void put_x16(const STREAM *p, const uint16_t num)
+{
+	_print_hex(p, (uint8_t*) &num, 2);
+}
+
+
+/** Send long as hex */
+void put_x32(const STREAM *p, const uint32_t num)
+{
+	_print_hex(p, (uint8_t*) &num, 4);
+}
+
+
+/** Send long long as hex */
+void put_x64(const STREAM *p, const uint64_t num)
+{
+	_print_hex(p, (uint8_t*) &num, 8);
+}
+
+
+
+// float variant doesn't make sense for 8-bit int
+
+/** Send unsigned int as float */
+void put_u16f(const STREAM *p, const uint16_t num, const uint8_t places)
+{
+	utoa(num, tmpstr, 10);
+	_putnf(p, places);
+}
+
+
+/** Send signed int as float */
+void put_i16f(const STREAM *p, const int16_t num, const uint8_t places)
+{
+	if (num < 0) {
+		p->tx('-');
+		itoa(-num, tmpstr, 10);
+	} else {
+		itoa(num, tmpstr, 10);
+	}
+
+	_putnf(p, places);
+}
+
+
+/** Send unsigned long as float */
+void put_u32f(const STREAM *p, const uint32_t num, const uint8_t places)
+{
+	ultoa(num, tmpstr, 10);
+	_putnf(p, places);
+}
+
+
+/** Send signed long as float */
+void put_i32f(const STREAM *p, const int32_t num, const uint8_t places)
+{
+	if (num < 0) {
+		p->tx('-');
+		ltoa(-num, tmpstr, 10);
+	} else {
+		ltoa(num, tmpstr, 10);
+	}
+
+	_putnf(p, places);
+}
+
+
+/** Print number in tmp string as float with given decimal point position */
+void _putnf(const STREAM *p, const uint8_t places)
+{
+	// measure text length
+	uint8_t len = 0;
+	while(tmpstr[len] != 0) len++;
+
+	int8_t at = len - places;
+
+	// print virtual zeros
+	if (at <= 0) {
+		p->tx('0');
+		p->tx('.');
+		while(at <= -1) {
+			p->tx('0');
+			at++;
+		}
+		at = -1;
+	}
+
+	// print the number
+	uint8_t i = 0;
+	while(i < len) {
+		if (at-- == 0) {
+			p->tx('.');
+		}
+
+		p->tx(tmpstr[i++]);
+	}
+}
+
+
+/** Print CR LF */
+void put_nl(const STREAM *p)
+{
+	p->tx(13);
+	p->tx(10);
+}

projects/lcdsnake_v2/lib/stream.h

@@ -0,0 +1,99 @@
+#pragma once
+
+//
+// Streams -- in this library -- are instances of type STREAM.
+//
+// A stream can be used for receiving and sending bytes, generally
+// it's a pipe to a device.
+//
+// They are designed for printing numbers and strings, but can
+// also be used for general data transfer.
+//
+// Examples of streams:
+// "uart.h" -> declares global variable "uart" which is a pointer to the UART stream
+// "lcd.h" -> declares a global variable "lcd" (pointer to LCD scho stream)
+//
+// Streams help avoid code duplication, since the same functions can be used
+// to format and print data to different device types.
+//
+
+#include <stdlib.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <avr/pgmspace.h>
+
+/** Stream structure */
+typedef struct {
+	void (*tx) (uint8_t b);
+	uint8_t (*rx) (void);
+} STREAM;
+
+
+/** Print string into a stream */
+void put_str(const STREAM *p, char* str);
+
+
+/** Print a programspace string into a stream */
+void put_str_P(const STREAM *p, const char* str);
+
+
+/** Send signed int8 */
+void put_u8(const STREAM *p, const uint8_t num);
+
+
+/** Send unsigned int8 */
+void put_i8(const STREAM *p, const int8_t num);
+
+
+/** Send unsigned int */
+void put_u16(const STREAM *p, const uint16_t num);
+
+
+/** Send signed int */
+void put_i16(const STREAM *p, const int16_t num);
+
+
+/** Send unsigned long */
+void put_u32(const STREAM *p, const uint32_t num);
+
+
+/** Send signed long */
+void put_i32(const STREAM *p, const int32_t num);
+
+
+/** Send unsigned int8 */
+void put_x8(const STREAM *p, const uint8_t num);
+
+
+/** Send int as hex */
+void put_x16(const STREAM *p, const uint16_t num);
+
+
+/** Send long as hex */
+void put_x32(const STREAM *p, const uint32_t num);
+
+
+/** Send long long as hex */
+void put_x64(const STREAM *p, const uint64_t num);
+
+
+// float variant doesn't make sense for 8-bit int
+
+/** Send unsigned int as float */
+void put_u16f(const STREAM *p, const uint16_t num, const uint8_t places);
+
+
+/** Send signed int as float */
+void put_i16f(const STREAM *p, const int16_t num, const uint8_t places);
+
+
+/** Send unsigned long as float */
+void put_u32f(const STREAM *p, const uint32_t num, const uint8_t places);
+
+
+/** Send signed long as float */
+void put_i32f(const STREAM *p, const int32_t num, const uint8_t places);
+
+
+/** Print CR LF */
+void put_nl(const STREAM *p);

projects/lcdsnake_v2/main.c

@@ -0,0 +1,428 @@
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <avr/pgmspace.h>
+#include <util/delay.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "lib/arduino_pins.h"
+#include "lib/calc.h"
+#include "lib/adc.h"
+#include "lib/lcd.h"
+#include "lib/debounce.h"
+
+// Buttons (to ground)
+#define BTN_LEFT     A0
+#define BTN_RIGHT    A1
+#define BTN_UP       A2
+#define BTN_DOWN     A3
+#define BTN_PAUSE    A4
+#define BTN_RESTART  A5
+
+// Debouncer channels for buttons
+// (Must be added in this order to debouncer)
+#define D_LEFT      0
+#define D_RIGHT     1
+#define D_UP        2
+#define D_DOWN      3
+#define D_PAUSE     4
+#define D_RESTART   5
+
+// Board size (!!! rows = 2x number of display lines, max 2*4 = 8 !!!)
+#define ROWS 8
+#define COLS 20
+
+// Delay between snake steps, in 10 ms
+#define STEP_DELAY 24
+
+// proto
+void update();
+void init_cgram();
+void init_gameboard();
+
+void init()
+{
+	// Randomize RNG
+	adc_init();
+	srand(adc_read_word(3));
+
+	// Init LCD
+	lcd_init();
+	init_cgram();  // load default glyphs
+
+	// Init game board.
+	init_gameboard();
+
+	// gamepad buttons
+	as_input_pu(BTN_LEFT);
+	as_input_pu(BTN_RIGHT);
+	as_input_pu(BTN_UP);
+	as_input_pu(BTN_DOWN);
+	as_input_pu(BTN_PAUSE);
+	as_input_pu(BTN_RESTART);
+
+	// add buttons to debouncer
+	debo_add_rev(BTN_LEFT);
+	debo_add_rev(BTN_RIGHT);
+	debo_add_rev(BTN_UP);
+	debo_add_rev(BTN_DOWN);
+	debo_add_rev(BTN_PAUSE);
+	debo_add_rev(BTN_RESTART);
+
+	// setup timer
+	TCCR0A = _BV(WGM01); // CTC
+	TCCR0B = _BV(CS02) | _BV(CS00);  // prescaler 1024
+	OCR0A = 156;  // interrupt every 10 ms
+	sbi(TIMSK0, OCIE0A);
+	sei();
+}
+
+
+/** timer 0 interrupt vector */
+ISR(TIMER0_COMPA_vect)
+{
+	debo_tick();  // poll debouncer
+	update();  // update and display
+}
+
+
+
+// sub-glyphs
+#define _HEAD_ 15, 21, 21, 30
+#define _BODY_ 15, 31, 31, 30
+#define _FOOD_ 10, 21, 17, 14
+//14, 17, 17, 14
+#define _NONE_  0,  0,  0,  0
+
+// complete glyphs for loading into memory
+
+// Only one food & one head glyph have to be loaded at a time.
+
+// Body - Body
+const uint8_t SYMBOL_BB[] PROGMEM = {_BODY_, _BODY_};
+
+// Body - None
+const uint8_t SYMBOL_BX[] PROGMEM = {_BODY_, _NONE_};
+const uint8_t SYMBOL_XB[] PROGMEM = {_NONE_, _BODY_};
+
+// Head - None
+const uint8_t SYMBOL_HX[] PROGMEM = {_HEAD_, _NONE_};
+const uint8_t SYMBOL_XH[] PROGMEM = {_NONE_, _HEAD_};
+
+// Body - Head
+const uint8_t SYMBOL_BH[] PROGMEM = {_BODY_, _HEAD_};
+const uint8_t SYMBOL_HB[] PROGMEM = {_HEAD_, _BODY_};
+
+// Head - Food
+const uint8_t SYMBOL_HF[] PROGMEM = {_HEAD_, _FOOD_};
+const uint8_t SYMBOL_FH[] PROGMEM = {_FOOD_, _HEAD_};
+
+// Food - None
+const uint8_t SYMBOL_FX[] PROGMEM = {_FOOD_, _NONE_};
+const uint8_t SYMBOL_XF[] PROGMEM = {_NONE_, _FOOD_};
+
+// Body - Food
+const uint8_t SYMBOL_BF[] PROGMEM = {_BODY_, _FOOD_};
+const uint8_t SYMBOL_FB[] PROGMEM = {_FOOD_, _BODY_};
+
+
+// board block (snake, food...)
+typedef enum {
+	bEMPTY = 0x00,
+	bHEAD = 0x01,
+	bFOOD = 0x02,
+	bBODY_LEFT = 0x80,
+	bBODY_RIGHT = 0x81,
+	bBODY_UP = 0x82,
+	bBODY_DOWN = 0x83,
+} block_t;
+
+// Snake direction
+typedef enum {
+	dLEFT = 0x00,
+	dRIGHT = 0x01,
+	dUP = 0x02,
+	dDOWN = 0x03,
+} dir_t;
+
+// Coordinate on board
+typedef struct {
+	int8_t x;
+	int8_t y;
+} coord_t;
+
+#define is_body(blk) (((blk) & 0x80) != 0)
+#define mk_body_dir(dir) (0x80 + (dir))
+
+// compare two coords
+#define coord_eq(a, b) (((a).x == (b).x) && ((a).y == (b).y))
+
+
+bool crashed;
+uint8_t snake_len;
+
+// y, x indexing
+block_t board[ROWS][COLS];
+
+coord_t head_pos;
+coord_t tail_pos;
+dir_t head_dir;
+
+const uint8_t CODE_BB = 0;
+const uint8_t CODE_BX = 1;
+const uint8_t CODE_XB = 2;
+const uint8_t CODE_H = 3;  // glyph with head, dynamic
+const uint8_t CODE_F = 4;  // glyph with food, dynamic
+const uint8_t CODE_XX = 32; // space
+
+
+// Set a block in board
+#define set_block_xy(x, y, block) do { board[y][x] = (block); } while(0)
+#define get_block_xy(x, y) board[y][x]
+#define get_block(pos) get_block_xy((pos).x, (pos).y)
+#define set_block(pos, block) set_block_xy((pos).x, (pos).y, (block))
+
+
+void init_cgram()
+{
+	// those will be always the same
+	lcd_glyph_P(CODE_BB, SYMBOL_BB);
+	lcd_glyph_P(CODE_BX, SYMBOL_BX);
+	lcd_glyph_P(CODE_XB, SYMBOL_XB);
+						lcd_glyph_P(5, SYMBOL_XF);
+}
+
+
+void place_food()
+{
+	while(1) {
+		const uint8_t xx = rand() % COLS;
+		const uint8_t yy = rand() % ROWS;
+
+		if (get_block_xy(xx, yy) == bEMPTY) {
+			set_block_xy(xx, yy, bFOOD);
+			break;
+		}
+	}
+}
+
+
+void init_gameboard()
+{
+	//erase the board
+	for (uint8_t x = 0; x < COLS; x++) {
+		for (uint8_t y = 0; y < ROWS; y++) {
+			set_block_xy(x, y, bEMPTY);
+		}
+	}
+
+	lcd_clear();
+
+	tail_pos = (coord_t) {.x = 0, .y = 0};
+
+	set_block_xy(0, 0, bBODY_RIGHT);
+	set_block_xy(1, 0, bBODY_RIGHT);
+	set_block_xy(2, 0, bBODY_RIGHT);
+	set_block_xy(3, 0, bHEAD);
+
+	head_pos = (coord_t) {.x = 3, .y = 0};
+
+	snake_len = 4; // includes head
+
+	head_dir = dRIGHT;
+	crashed = false;
+
+	place_food();
+}
+
+
+uint8_t presc = 0;
+
+bool restart_held;
+bool pause_held;
+bool paused;
+void update()
+{
+	if (debo_get_pin(D_RESTART)) {
+
+		if (!restart_held) {
+			// restart
+			init_gameboard();
+			presc = 0;
+			restart_held = true;
+		}
+
+	} else {
+		restart_held = false;
+	}
+
+	if (debo_get_pin(D_PAUSE)) {
+
+		if (!pause_held) {
+			paused ^= true;
+			pause_held = true;
+		}
+
+	} else {
+		pause_held = false;
+	}
+
+	if(!crashed && !paused) {
+
+		// resolve movement direction
+		if (debo_get_pin(D_LEFT))
+			head_dir = dLEFT;
+		else if (debo_get_pin(D_RIGHT))
+			head_dir = dRIGHT;
+		else if (debo_get_pin(D_UP))
+			head_dir = dUP;
+		else if (debo_get_pin(D_DOWN))
+			head_dir = dDOWN;
+
+		// time's up for a move
+		if (presc++ == STEP_DELAY) {
+			presc = 0;
+
+			// move snake
+			const coord_t oldpos = head_pos;
+
+			switch (head_dir) {
+				case dLEFT:  head_pos.x--; break;
+				case dRIGHT: head_pos.x++; break;
+				case dUP:    head_pos.y--; break;
+				case dDOWN:  head_pos.y++; break;
+			}
+
+			bool do_move = false;
+			bool do_grow = false;
+
+			if (head_pos.x < 0 || head_pos.x >= COLS || head_pos.y < 0 || head_pos.y >= ROWS) {
+				// ouch, a wall!
+				crashed = true;
+			} else {
+				// check if tile occupied or not
+				if (coord_eq(head_pos, tail_pos)) {
+					// head moved in previous tail, that's OK.
+					do_move = true;
+				} else {
+					// moved to other tile than tail
+					switch (get_block(head_pos)) {
+
+						case bFOOD:
+							do_grow = true;  // fall through
+						case bEMPTY:
+							do_move = true;
+							break;
+
+						default: // includes all BODY_xxx
+							crashed = true;  // snake crashed into some block
+					}
+				}
+			}
+
+			if (do_move) {
+				// Move tail
+				if (do_grow) {
+					// let tail as is
+					snake_len++; // grow the counter
+				} else {
+					// tail dir
+					dir_t td = get_block(tail_pos) & 0xF;
+
+					// clean tail
+					set_block(tail_pos, bEMPTY);
+
+					// move tail based on old direction of tail block
+					switch (td) {
+						case dLEFT:  tail_pos.x--; break;
+						case dRIGHT: tail_pos.x++; break;
+						case dUP:    tail_pos.y--; break;
+						case dDOWN:  tail_pos.y++; break;
+					}
+				}
+
+				// Move head
+				set_block(head_pos, bHEAD);  // place head in new pos
+				set_block(oldpos, mk_body_dir(head_dir));  // directional body in old head pos
+
+				if (do_grow) {
+					// food eaten, place new
+					place_food();
+				}
+			}
+		}
+	} // end !crashed
+
+
+	// Render the board
+	for (uint8_t r = 0; r < ROWS / 2; r++)	{
+		lcd_xy(0, r);
+		for (uint8_t c = 0; c < COLS; c++)	{
+			const block_t t1 = get_block_xy(c, r * 2);
+			const block_t t2 = get_block_xy(c, (r * 2) + 1);
+
+			uint8_t code = '!';  // ! marks fail
+
+			if ((t1 == bEMPTY) && (t2 == bEMPTY)) {
+				code = CODE_XX;
+				if (crashed) code = '*';
+			} else if (is_body(t1) && is_body(t2))
+				code = CODE_BB;
+			else if (is_body(t1) && (t2 == bEMPTY))
+				code = CODE_BX;
+			else if (t1 == bEMPTY && is_body(t2))
+				code = CODE_XB;
+			else if ((t1 == bFOOD) || (t2 == bFOOD)) {
+				// one is food
+
+				code = CODE_F;
+
+				if (t1 == bFOOD) {
+					if (t2 == bEMPTY)
+						lcd_glyph_P(code, SYMBOL_FX);
+					else if (t2 == bHEAD)
+						lcd_glyph_P(code, SYMBOL_FH);
+					else if (is_body(t2))
+						lcd_glyph_P(code, SYMBOL_FB);
+				} else { // t2 is food
+					if (t1 == bEMPTY)
+						lcd_glyph_P(code, SYMBOL_XF);
+					else if (t1 == bHEAD)
+						lcd_glyph_P(code, SYMBOL_HF);
+					else if (is_body(t1))
+						lcd_glyph_P(code, SYMBOL_BF);
+				}
+				lcd_xy(c,r);
+
+			} else if ((t1 == bHEAD )|| (t2 == bHEAD)) {
+				// one is head
+
+				code = CODE_H;
+
+				if (t1 == bHEAD) {
+					if (t2 == bEMPTY)
+						lcd_glyph_P(code, SYMBOL_HX);
+					else if (is_body(t2))
+						lcd_glyph_P(code, SYMBOL_HB);
+				} else { // t2 is head
+					if (t1 == bEMPTY)
+						lcd_glyph_P(code, SYMBOL_XH);
+					else if (is_body(t1))
+						lcd_glyph_P(code, SYMBOL_BH);
+				}
+
+				lcd_xy(c,r);
+			}
+
+			lcd_putc(code);
+		}
+	}
+}
+
+void main()
+{
+	init();
+
+	while(1); // timer does everything
+}