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| // timer_demo2.c |
| // ------------- |
| // |
| // Example file for ATmega88 (and similar AVR chips) demonstrating how to use |
| // timer interrupt to realize Clocks with LED display. |
| // |
| // The program uses TIMER1 to generate interrupts and the interrupt routine counts |
| // fragments of second, seconds, tens of seconds etc. In the same interrupt routine |
| // the display multiplex is done. We use 4 digit 7 segment display. |
| // Common anodas are connected to LED_DIGITS_PORT and segments are connected |
| // to LED_SEGMENTS_PORT (use serial rezistors here, cca 100 OHM). |
| // |
| // (c) miho 2014 http://www.mlab.cz |
| // |
| // History |
| // 2014 01 31 - First demo |
| |
| |
| // System Configuration |
| #define F_CPU 4000000 // Do not forget to set FUSEs to external XTAL osc with DIV/8 off and connect xtal |
| |
| // LED Display - Configuration |
| #define LED_DIGITS_PORT C // Digits Port (common anodas) |
| #define LED_DIGITS 4 // Number of display digits (1..8) |
| #define LED_SEGMENTS_PORT D // Segments Port (catodas) |
| #define LED_SEGMENTS 8 // Usualy 7 or 8 (bit 0 is A) |
| #define TICKS_PER_SEC 500 // Number of interrupts per second ( >250 to look steady) |
| |
| |
| // -------------- DO NOT EDIT BELOW THIS LINE -------------- |
| |
| |
| // LED Display - Internal Defs |
| #define LED_DIGITS_MASK ((1<<LED_DIGITS)-1) // For 4 digits 0x0F=0b00001111 |
| #define LED_SEGMENTS_MASK ((1<<LED_SEGMENTS)-1) // For 7 segments 0x7F=0b01111111 |
| |
| |
| // LED Display - Verify Configuration |
| #if (F_CPU / 64 % TICKS_PER_SEC) |
| #error "TICKS_PER_SEC" should be chosen so that "F_CPU / 64 / TICKS_PER_SEC" is a whole number! |
| #endif |
| #if ( (F_CPU / 64 / TICKS_PER_SEC) > 65536) |
| #error "TICKS_PER_SEC" should be chosen bigger (timer is long 16bit only)! |
| #endif |
| |
| |
| // Library Headers |
| #include <avr/interrupt.h> |
| |
| |
| // Compatibility ATmega8 / ATmega88 |
| #ifndef TIMSK |
| #define TIMSK TIMSK1 |
| #endif |
| |
| |
| // Macro for Port (enables to easily define IO signals) |
| #define GLUE(A,B) A##B |
| #define DDR(PORT_LETTER) GLUE(DDR, PORT_LETTER) // Makes DDRC from DDR(C) etc. |
| #define PORT(PORT_LETTER) GLUE(PORT,PORT_LETTER) // Makes PORTC from PORT(C) |
| #define PIN(PORT_LETTER) GLUE(PIN, PORT_LETTER) // Makes PINC from PIN(C) |
| |
| |
| // 7 Segment Decoder |
| unsigned char Convert(unsigned char Number) |
| { |
| // 7 Segment Decoder Table |
| const unsigned char Decoder[] = |
| { |
| // HGFEDCBA |
| 0b00111111, // 0 |
| 0b00000011, // 1 |
| 0b01101101, // 2 |
| 0b01100111, // 3 |
| 0b01010011, // 4 |
| 0b01110110, // 5 |
| 0b01111110, // 6 |
| 0b00100011, // 7 |
| 0b01111111, // 8 |
| 0b01110111 // 9 |
| }; |
| |
| // Decoding Function |
| if(Number<sizeof(Decoder)) return Decoder[Number]; else return 0; |
| } |
| |
| |
| // Global Variable - Time Counters |
| volatile unsigned int Fractions; // 1/100s |
| volatile unsigned char Seconds, Seconds10; // Seconds and tens of seconds |
| volatile unsigned char Minutes, Minutes10; // Minutes and tens of minutes |
| volatile unsigned char Hours, Hours10; // Hours and tens of hours |
| |
| |
| // Global Variable - Display Multiplex |
| volatile unsigned char DisplayDigit; // Multiplex state 0 1 2 3 (binary counter) |
| volatile unsigned char DisplayDigitMask; // Multiplex state 1 2 4 8 (mask 1 from N) |
| |
| |
| // Interrupt Routine for TIMER1 Output Compare A |
| // Activated 500 per second |
| ISR(TIMER1_COMPA_vect) |
| { |
| // Every 1/500s |
| Fractions++; |
| if (Fractions>(TICKS_PER_SEC-1)) |
| { |
| // Every 1s |
| Fractions=0; |
| Seconds++; |
| if (Seconds>9) |
| { |
| // Every 10s |
| Seconds = 0; |
| Seconds10++; |
| if (Seconds10>5) |
| { |
| // Every 1m |
| Seconds10=0; |
| Minutes++; |
| if (Minutes>9) |
| { |
| // Every 10m |
| Minutes=0; |
| Minutes10++; |
| if (Minutes10>5) |
| { |
| // Every 1h |
| Minutes10=0; |
| Hours++; |
| if (Hours10==2 && Hours>3) |
| { |
| // Every Day |
| Hours=0; |
| Hours10=0; |
| } |
| if (Hours>9) |
| { |
| // At 10 and 20 hours |
| Hours=0; |
| Hours10++; |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| // LED display time multiplex - next digit |
| // 500x per second |
| DisplayDigit++; |
| DisplayDigitMask<<=1; |
| if (DisplayDigit == LED_DIGITS) |
| { |
| DisplayDigit = 0; |
| DisplayDigitMask = 1; |
| } |
| |
| // Get Segment Combination for Current Digit |
| unsigned char Segments=0; |
| switch(DisplayDigit) |
| { |
| case 0: Segments = Convert(Seconds); |
| break; |
| case 1: Segments = Convert(Seconds10); |
| break; |
| case 2: Segments = Convert(Minutes); |
| break; |
| case 3: Segments = Convert(Minutes10); |
| } |
| |
| // LED display update - All digits off |
| PORT(LED_DIGITS_PORT) &= ~LED_DIGITS_MASK; // common anoda 0=off |
| // LED display update - New segments combination |
| PORT(LED_SEGMENTS_PORT) = (PORT(LED_SEGMENTS_PORT) & ~LED_SEGMENTS_MASK) | (~Segments & LED_SEGMENTS_MASK); |
| // LED display update - One digit on |
| PORT(LED_DIGITS_PORT) |= (LED_DIGITS_MASK & DisplayDigitMask); // (common anoda 1=on) |
| } |
| |
| |
| // Main |
| int main() |
| { |
| // Enable LED Display Output |
| DDR(LED_SEGMENTS_PORT) |= LED_SEGMENTS_MASK; // 8 segments 0b11111111 |
| DDR(LED_DIGITS_PORT) |= LED_DIGITS_MASK; // 4 digits 0b00001111 |
| |
| // Set MAX value for Timer1 |
| OCR1A = (F_CPU+64/2)/64/TICKS_PER_SEC-1; // 1/500s |
| |
| // Set Timer1 to CTC with presacaller 1/64 |
| // CTC Mmode counts from 0 to value stored in OCR1A |
| // and generates interrupt every time it goes back to 0 |
| TCCR1B |= (1<<CS11) | (1<<CS10) | (1<<WGM12); |
| |
| // Enable Interrupt for Timer1 OCRA |
| TIMSK |= (1<<OCIE1A); |
| |
| // Enable Global (CPU) Interrupt |
| sei(); |
| |
| // Main Loop |
| for(;;) |
| { |
| // Do any job here |
| } |
| |
| return 0; |
| } |