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Table of Contents
7-segment numeric display
The Study board is equipped with 7-segment LED display and its driver A6275 (datasheet). The driver is connected to controller ports PORTC and PORTG.
the schematics is shown below. The latch is connected to PORTG2, Serial to PORTC6 and clock to PORTC7.
Example 1
/* Basic ver 3 demo program 7-seg function and demo Raivo Sell/Erki Leitaru */ #define F_CPU 14745600UL #include <avr/io.h> #include <util/delay.h> #define SET(x) |= (1<<x) //defineeritakse kõrge bit pordis x #define CLR(x) &=~(1<<x) //defineeritakse madal bit pordis x #define bit_get(p,m) ((p) & (m)) //returns 1 if bit is set, otherwise returns 0 #define BIT(x) (0x01 << (x)) void write_display (void); void nop_delay(int count); int i;//for cycle int digit;//digit to display on segment int nr;//segment map representation of the digit int delta;//to create a counting effect int num = 0; char buffer[7]; void nop_delay(int count){ unsigned int j; for (j=0; j<count;j++) {asm volatile ("nop");} } void write_display (void) { switch (digit) //table read to get segment map representation of the digit { case 0 : nr = 0b00111111;break; //every bit corresponds to one segment case 1 : nr = 0b00000110;break; //"1" case 2 : nr = 0b01011011;break; //"2" and so on case 3 : nr = 0b01001111;break; case 4 : nr = 0b01100110;break; case 5 : nr = 0b01101101;break; case 6 : nr = 0b01111100;break; case 7 : nr = 0b00000111;break; case 8 : nr = 0b01111111;break; case 9 : nr = 0b01100111;break; default: nr = 0b01111001;//E } PORTG CLR (2); //latch low for(i=7; i>=0; i--) //for every bit in the byte { //if bit is set, sets the data out pin if (bit_get(nr, BIT(i))) PORTC SET (6); //serial out else PORTC CLR (6); //serial out PORTC SET (7); //clock high nop_delay(8);//series of one cycle delays to ensure required timing (according to datasheet) PORTC CLR (7); //clock low nop_delay(8); } PORTG SET (2); //latch high } int main(void){ //7-seg init PORTC = 0xFF; // set output high -> turn all LEDs off DDRC = 0xF8; // PC0...PC2 -> input; PC3...PC5 -> output for LED; PC7 & PC6 outputs for clock and data DDRG = 0x04;//PG2 is latch output digit = 8; delta = 1;//increment or decrement while(1) { num++; _delay_ms(1000); digit=digit+delta;//change digit by delta if(digit>8) {delta=-1*delta;};//upper limit if(digit<1) {delta=-1*delta;};//lower limit write_display(); } }
Example 2
this example does not contain global variables and only functions are used. It is more easy to copy the functions into user program. All variables are 8 bit where possible.
// // Simple up/down counting single 7-segment digit example. // // Raivo Sell, Erki Leitaru, Mikk Leini // // 2009 // #define F_CPU 14745600UL // Include avrlibc #include <avr/io.h> #include <util/delay.h> // Macros for bit manipulation #define BIT(x) (1 << (x)) #define SET(x) |= BIT(x) #define CLR(x) &= ~BIT(x) #define SETTO(value, bit, to) value = ((to) ? value | BIT(bit) : value & ~BIT(bit)) #define ISSET(value, bit) ((value) & (BIT(bit))) // // Delay cycle // On each cycle "no-operation" instruction is executed // void nop_delay(unsigned int count) { for (unsigned int i = 0; i < count; i++) { asm volatile ("nop"); } } // // 7 segment display initialization // void segment_diplay_init(void) { // Port C pin 7 - clock output, pin 6 data output DDRC |= 0xC0; // Port G pin 2 - latch output DDRG |= 0x04; } // // Digit writing to 7 segment display // void segment_display_write(unsigned char digit) { unsigned char map; // Decimal to segment map switch (digit) { case 0 : map = 0b00111111; break; // Every bit corresponds to one segment case 1 : map = 0b00000110; break; // "1" case 2 : map = 0b01011011; break; // "2" case 3 : map = 0b01001111; break; // "3" and so on case 4 : map = 0b01100110; break; case 5 : map = 0b01101101; break; case 6 : map = 0b01111100; break; case 7 : map = 0b00000111; break; case 8 : map = 0b01111111; break; case 9 : map = 0b01100111; break; default: map = 0b01111001; // E like Error } // Latch low PORTG CLR(2); // Send every bit in the byte. MSB (most significant bit) first. for (signed char i = 7; i >= 0; i--) { // If bit is set, sets the data out pin, otherwise not SETTO(PORTC, 6, ISSET(map, i)); // Clock high for certain period PORTC SET(7); nop_delay(8); // Clock low for certain period PORTC CLR(7); nop_delay(8); } // Latch high PORTG SET(2); } // // Program entrance function // int main(void) { unsigned char digit = 0; // Digit to display on segment signed char delta = 1; // Digit modifying value // 7 segment display initialization segment_diplay_init(); // Endless loop while (1) { // Write digit segment_display_write(digit); // Increase digit value by delta (which can be negative also) digit += delta; // Swap counting direction on 0 and 9 if (digit == 0) delta = +1; if (digit == 9) delta = -1; // Wait 1000 ms _delay_ms(1000); } }
Example 3
“pinops.h” library is used to simplify the port and pin usage. See here for more detail description.
LED driver is replaced by the avrlibc driver.
// // Simple up/down counting single 7-segment digit example. // // Raivo Sell, Erki Leitaru, Mikk Leini // // 2009 // // Include avrlibc #include <avr/io.h> #include <util/delay.h> // Include common library #include "pinops.h" /* PS! For distance Lab use: #include <util/pinops.h> */ // Configure pins #define SEGMENT_DISPLAY_LATCH PORTPIN(G, 2) #define SEGMENT_DISPLAY_DATA_OUT PORTPIN(C, 6) #define SEGMENT_DISPLAY_CLOCK PORTPIN(C, 7) // // 7 segment display initialization // void segment_display_init(void) { // Set latch, data out and clock pins as output setup_output_pin(SEGMENT_DISPLAY_LATCH); setup_output_pin(SEGMENT_DISPLAY_DATA_OUT); setup_output_pin(SEGMENT_DISPLAY_CLOCK); } // // Digit writing to 7 segment display // void segment_display_write(unsigned char digit) { unsigned char map; // Decimal to segment map switch (digit) { case 0 : map = 0b00111111; break; // Every bit corresponds to one segment case 1 : map = 0b00000110; break; // "1" case 2 : map = 0b01011011; break; // "2" case 3 : map = 0b01001111; break; // "3" and so on case 4 : map = 0b01100110; break; case 5 : map = 0b01101101; break; case 6 : map = 0b01111100; break; case 7 : map = 0b00000111; break; case 8 : map = 0b01111111; break; case 9 : map = 0b01100111; break; default: map = 0b01111001; // E like Error } // Latch low clear_pin(SEGMENT_DISPLAY_LATCH); // Send every bit in the byte. MSB (most significant bit) first. for (signed char i = 7; i >= 0; i--) { // If bit is set, sets the data out pin, otherwise not set_pin_to(SEGMENT_DISPLAY_DATA_OUT, IS_BIT_SET(map, i)); // Clock high for certain period set_pin(SEGMENT_DISPLAY_CLOCK) _delay_us(1); // Clock low for certain period clear_pin(SEGMENT_DISPLAY_CLOCK) _delay_us(1); } // Latch high set_pin(SEGMENT_DISPLAY_LATCH); } // // Program entrance function // int main(void) { unsigned char digit = 0; // Digit to display on segment signed char delta = 1; // Digit modifying value //digit = int (void) { return 2; }; // 7 segment display initialization segment_display_init(); // Endless loop while (1) { // Write digit segment_display_write(digit); // Increase digit value by delta (which can be negative also) digit += delta; // Swap counting direction on 0 and 9 if (digit == 0) delta = +1; if (digit == 9) delta = -1; // Wait 1000 ms _delay_ms(1000); } }
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