80 lines
2.5 KiB
C
80 lines
2.5 KiB
C
#include <avr/io.h>
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// #define FIRST_LETTER_IMPL(x) #x[0]
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// #define FIRST_LETTER(x) FIRST_LETTER_IMPL(x)
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// #define PORT_LETTER(PIN) FIRST_LETTER(PIN)
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// global registers
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#define SET(register, bit) register |= 1 << bit
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#define CLEAR(register, bit) register &= ~(1 << bit)
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#define TEST(register, bit) register & 1 << bit
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#define TOGGLE(register, bit) register ^= 1 << bit
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// actions on ports
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#define TEST_PIN(port, bit) TEST(PIN ## port, bit)
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#define TOGGLE_PIN(port, bit) SET(PIN ## port, bit)
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#define MODE_INPUT(port, bit) CLEAR(DDR ## port, bit)
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#define MODE_OUTPUT(port, bit) SET(DDR ## port, bit)
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#define IS_PIN_SET(port, bit) (TEST_PIN(port, bit)) == 0
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#define IS_PIN_CLEAR(port, bit) (TEST_PIN(port, bit)) == 1
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#define TURN_ON(_PORT, BIT) SET(PORT ## _PORT, BIT)
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#define TURN_OFF(_PORT, BIT) CLEAR(PORT ## _PORT, BIT)
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// LEDs
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#define TURN_ON_LED(bit) SET(PORTB, bit)
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#define TURN_OFF_LED(bit) CLEAR(PORTB, bit)
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#define TOGGLE_LED(led) TOGGLE_PIN(B, led)
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// ELEMENTS
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#define D1 0
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#define D2 1
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#define D3 2
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#define D4 4
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#define SW1 2
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#define SW2 4
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// TIME
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#define PRESCALE_VALUE 1024
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#if (PRESCALE_VALUE == 1)
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#define PRESCALE_SET (1 << CS10)
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#elif (PRESCALE_VALUE == 8)
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#define PRESCALE_SET (1 << CS11)
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#elif (PRESCALE_VALUE == 64)
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#define PRESCALE_SET (1 << CS10) | (1 << CS11)
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#elif (PRESCALE_VALUE == 256)
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#define PRESCALE_SET (1 << CS12)
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#elif (PRESCALE_VALUE == 1024)
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#define PRESCALE_SET (1 << CS10) | (1 << CS12)
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#endif
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#define TIME_MS(ms) (((F_CPU / PRESCALE_VALUE) * ms) / 1000)
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int main() {
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MODE_OUTPUT(B, D2);
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TCCR1B |= (1 << WGM12); // set timer in CTC (Clear Time on Compare) mode
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// -> Table 16-4 : use bit WGM12 to set mode ctc
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// -> 16.11.2 : bit WGM12 is located in register TCCR1B
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OCR1A = TIME_MS(500); // set CTC compare value
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// -> Table 16-4 : the value to reset the timer is the Output Compare Registers OCR1A
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TCCR1B |= (PRESCALE_SET);
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while(1) {
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if (TIFR1 & (1 << OCF1A)) { // when comparison has occured, bit OCF1A is set
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// -> 16.2.1 : "The compare match event will also set the Compare Match Flag (OCF1A/B) which can be used to generate an Output Compare interrupt request"
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// -> 16.11.9 : bit OCF1A is in register TIFR1
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TOGGLE_LED(D2); // toggle using PINx register
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TIFR1 = (1 << OCF1A); // clear the CTC flag
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// -> 16.11.9 : "OCF1A can be cleared by writing a logic one to its bit location"
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}
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}
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}
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