init mod02 x02
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hugogogo
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module02/ex02/Makefile
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module02/ex02/Makefile
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include ../../Makefile
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module02/ex02/main.c
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module02/ex02/main.c
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#include <avr/io.h>
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#include <util/delay.h>
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#include <avr/interrupt.h>
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// mathematics
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#define DIV_ROUND_CLOSEST(n, d) ((((n) < 0) == ((d) < 0)) ? (((n) + (d)/2)/(d)) : (((n) - (d)/2)/(d))) // https://stackoverflow.com/a/18067292
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// stringify
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#define STRINGIFY_HELPER(x) #x
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#define STRINGIFY(x) STRINGIFY_HELPER(x)
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// concatenate
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#define CONCAT_HELPER(x, y) x ## y
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#define CONCAT(x, y) CONCAT_HELPER(x, y)
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// get argument
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#define ARG_1(v1, v2) v1
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#define ARG_2(v1, v2) v2
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#define GET_PORT(args) ARG_1 args
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#define GET_BIT(args) ARG_2 args
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// // version with "LED1 B, D1" without parenthesis
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// #define ARG_1(v1, ...) v1
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// #define ARG_2(v1, v2, ...) v2
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// #define GET_PORT(...) ARG_1(__VA_ARGS__)
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// #define GET_BIT(...) ARG_2(__VA_ARGS__)
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// actions on 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 elements
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#define SET_ELEM(elem) SET(CONCAT(PORT, GET_PORT(elem)), GET_BIT(elem))
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// #define SET_ELEM(...) SET(CONCAT(PORT, GET_PORT(__VA_ARGS__)), GET_BIT(__VA_ARGS__)) // version for "LED1 B, D1" without parenthesis
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#define CLEAR_ELEM(elem) CLEAR(CONCAT(PORT, GET_PORT(elem)), GET_BIT(elem))
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#define TEST_ELEM(elem) TEST(CONCAT(PORT, GET_PORT(elem)), GET_BIT(elem))
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#define TOGGLE_ELEM(elem) TOGGLE(CONCAT(PORT, GET_PORT(elem)), GET_BIT(elem))
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#define MODE_OUTPUT(elem) SET(CONCAT(DDR, GET_PORT(elem)), GET_BIT(elem))
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#define MODE_INPUT(elem) CLEAR(CONCAT(DDR, GET_PORT(elem)), GET_BIT(elem))
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#define TOGGLE_PIN(elem) SET(CONCAT(PIN, GET_PORT(elem)), GET_BIT(elem))
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#define TEST_PIN(elem) (TEST(CONCAT(PIN, GET_PORT(elem)), GET_BIT(elem)))
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#define IS_PIN_SET(elem) (TEST_PIN(elem) == 0)
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#define IS_PIN_CLEAR(elem) (TEST_PIN(elem) == 1)
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// bits
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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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// elements (port, bit)
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// #define LED1 B, D1
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#define LED1 (B, D1)
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#define LED2 (B, D2)
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#define LED3 (B, D3)
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#define LED4 (B, D4)
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#define BUTTON1 (D, SW1)
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#define BUTTON2 (D, SW2)
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// USART
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// Table 20-1 : Baud Rate Calculation
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#define USART_BAUDRATE 115200
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#define BAUD_PRESCALER (DIV_ROUND_CLOSEST(F_CPU, (16 * USART_BAUDRATE)) - 1)
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// Table 20-8 : Mode Selection (USART Mode SELect)
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#define ASYNCHRONOUS (0<<UMSEL01 | 0<<UMSEL00)
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#define SYNCHRONOUS (0<<UMSEL01 | 1<<UMSEL00)
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// Table 20-9 : Parity Bit Selection (USART Parity Mode)
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#define PARITY_DISABLED (0<<UPM01 | 0<<UPM00)
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#define PARITY_EVEN (1<<UPM01 | 0<<UPM00)
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#define PARITY_ODD (1<<UPM01 | 1<<UPM00)
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// Table 20-10 : Stop Bit Selection (USART Stop Bit Select)
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#define STOP_ONE_BIT (0<<USBS0)
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#define STOP_TWO_BIT (1<<USBS0)
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// Table 20-11 : Data Bit Selection (USART Character SiZe)
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#define DATA_FIVE_BIT (0<<UCSZ02 | 0<<UCSZ01 | 0<<UCSZ00)
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#define DATA_SIX_BIT (0<<UCSZ02 | 0<<UCSZ01 | 1<<UCSZ00)
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#define DATA_SEVEN_BIT (0<<UCSZ02 | 1<<UCSZ01 | 0<<UCSZ00)
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#define DATA_EIGHT_BIT (0<<UCSZ02 | 1<<UCSZ01 | 1<<UCSZ00)
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#define DATA_NINE_BIT (1<<UCSZ02 | 1<<UCSZ01 | 1<<UCSZ00)
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// 20.11.3 : USART Control and Status Register B (UCSRnB)
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#define RECEIVER_DISABLED (0<<RXEN0)
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#define RECEIVER_ENABLED (1<<RXEN0)
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#define TRANSMITTER_DISABLED (0<<TXEN0)
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#define TRANSMITTER_ENABLED (1<<TXEN0)
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// TIMER
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#define PERIOD 2000
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#define TIME_MS(ms) (((F_CPU / PRESCALE_VALUE) * ms) / 1000)
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#define PRESCALE_VALUE 1024 // can be 1, 8, 64, 256, 1024
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// table 16-5 : prescale sets
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#define PRESCALE_SET(value) \
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((value) == 1 ? (0<<CS12 | 0<<CS11 | 1<<CS10) : \
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(value) == 8 ? (0<<CS12 | 1<<CS11 | 0<<CS10) : \
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(value) == 64 ? (0<<CS12 | 1<<CS11 | 1<<CS10) : \
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(value) == 256 ? (1<<CS12 | 0<<CS11 | 0<<CS10) : \
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(value) == 1024? (1<<CS12 | 0<<CS11 | 1<<CS10) : \
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(0<<CS12 | 0<<CS11 | 0<<CS10))
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// Table 16-4 : Waveform Generation Mode Bit Description
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#define CTC_TOP_OCR1A_IN_TCCR1B (0<<WGM13 | 1<<WGM12)
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#define CTC_TOP_OCR1A_IN_TCCR1A (0<<WGM11 | 0<<WGM10)
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#define CTC_TOP_ICR1_IN_TCCR1B (1<<WGM13 | 1<<WGM12)
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#define CTC_TOP_ICR1_IN_TCCR1A (0<<WGM11 | 0<<WGM10)
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#define FAST_PWM_TOP_OCR1A_IN_TCCR1B (1<<WGM13 | 1<<WGM12)
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#define FAST_PWM_TOP_OCR1A_IN_TCCR1A (1<<WGM11 | 1<<WGM10)
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#define FAST_PWM_TOP_ICR1_IN_TCCR1B (1<<WGM13 | 1<<WGM12)
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#define FAST_PWM_TOP_ICR1_IN_TCCR1A (1<<WGM11 | 0<<WGM10)
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#define INTERRUPT_ENABLE_CHANNEL_A (1 << OCIE1A)
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#define INTERRUPT_DISABLE_CHANNEL_A (0 << OCIE1A)
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// END MACROS
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void uart_init() {
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UBRR0H = (unsigned char) (BAUD_PRESCALER >> 8); // 20.11.5 : UBRRnL and UBRRnH – USART Baud Rate Registers
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UBRR0L = (unsigned char) BAUD_PRESCALER;
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UCSR0C |= ASYNCHRONOUS | PARITY_DISABLED | STOP_ONE_BIT | DATA_EIGHT_BIT; // 20.11.4 : set Frame Format
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UCSR0B |= RECEIVER_DISABLED | TRANSMITTER_ENABLED; // 20.11.3 : enable Receiver and/or Transmitter
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}
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void uart_tx(char c) {
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while (TEST(UCSR0A, UDRE0) == 0); // 20.11.2 : do nothing until UDR emission buffer is empty, if UDREn flag is 1, UCSRnA register is empty
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UDR0 = (unsigned char) c; // 20.11.1 : Put data into buffer, UDRn – USART I/O Data Register (read and write)
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}
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void uart_printstr(const char* str) {
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while (*str) {
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uart_tx(*str);
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str++;
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}
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}
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// print hello world, on serial port, every 2 seconds, with empty infinite loop
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// `screen /dev/ttyUSB0 115200`
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int main() {
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uart_init();
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TCCR1A |= CTC_TOP_OCR1A_IN_TCCR1A; // Table 16-4 : set timer in CTC (Clear Time on Compare) mode
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TCCR1B |= CTC_TOP_OCR1A_IN_TCCR1B;
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sei(); // enable global interrupts (https://www.nongnu.org/avr-libc/user-manual/group__avr__interrupts.html#gaad5ebd34cb344c26ac87594f79b06b73)
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TIMSK1 |= INTERRUPT_ENABLE_CHANNEL_A; // 16.11.8 : enables the Timer1 Compare Match A interrupt, this makes the MCU react when OCR1A == TCNT1 by calling TIMER1_COMPA_vect
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OCR1A = TIME_MS(PERIOD); // Table 16-4 : set CTC compare value on channel A, the counter is cleared to zero when the counter value (TCNT1) matches the OCR1A register
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TCCR1B |= (PRESCALE_SET(PRESCALE_VALUE)); // 16.4 : set timer according to prescale value, in register TCCR1B, table 16-5 : prescale sets
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while(1);
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}
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// ISR interrupt macro : https://www.nongnu.org/avr-libc/user-manual/group__avr__interrupts.html
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ISR(TIMER1_COMPA_vect) { // Table 12-7 : we select the code for timer 1 on channel A
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uart_printstr("Hello World!");
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}
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