Generate a PWM signal for the display
Generate a variable duty cycle PWM signal for the dimmable display backlight at a frequency of 1.25kHz. For demo und testing purposes PD5 is currently fading between 0 and 100%.
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3 changed files with 75 additions and 0 deletions
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.gitignore
vendored
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.gitignore
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*.o
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*.elf
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*.hex
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firmware/src/Makefile
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firmware/src/Makefile
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.SUFFIXES:
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MCU := atmega328p
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PROGRAMMER := usbtiny
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TARGET := main.hex
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BIN := main.elf
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OBJ := main.o
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SHELL := sh
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CC := avr-gcc
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OBJCOPY := avr-objcopy
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SIZE := avr-size
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AVRDUDE := avrdude
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CFLAGS := -mmcu=$(MCU) -Os -Wall -Werror -Wextra -Wpedantic
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all: $(TARGET)
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$(TARGET): $(BIN)
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${OBJCOPY} -O ihex -j .text -j .data $< $@
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$(BIN): $(OBJ)
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$(CC) $(CFLAGS) $< -o $@
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%.o: %.c
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$(CC) $(CFLAGS) -Os -c $< -o $@
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.PHONY: flash clean check size
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flash: $(TARGET) size
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$(AVRDUDE) -p $(MCU) -c $(PROGRAMMER) -U flash:w:$<:a
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clean:
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$(RM) main.o main.elf main.hex
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check:
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cppcheck main.c
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size: $(BIN)
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$(SIZE) --format=avr --mcu=$(MCU) $<
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firmware/src/main.c
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firmware/src/main.c
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#define F_CPU 8000000UL
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#include <avr/io.h>
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#include <util/delay.h>
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#include <stdbool.h>
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int main(void) {
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// FastPWM: 1.25kHz
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TCCR0A = (1 << WGM01) | (1 << WGM00) | (1 << COM0B1);
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TCCR0B = (1 << CS01) | (1 << WGM02); // prescaler = 8;
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OCR0A = 100;
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OCR0B = 10;
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DDRD |= (1 << PD5);
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bool reverse = 0;
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while (1) {
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_delay_ms(1);
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if (OCR0B > 100)
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reverse = !reverse;
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if (reverse)
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OCR0B++;
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else
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if (OCR0B > 0)
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OCR0B--;
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else
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reverse = !reverse;
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}
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}
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