/* Program: freq_cnt.c Function: Frequency Counter Hardware: ATMega 16 running on +5V with a 2x16 LCD plus external counter, counting gate and gate time generator Crystal: 4.096 MHz History: 10.05.2005 LCD works in 8bit mode 11.05.2005 4 Bit mode implemented tested for LCD Counting works for internal 16bit counter 12.05.2005 Counting works for all 24 bit (external + internal counter) 14.05.2005 Mode selection for different prescalers implemented and tested -> Version 1.0 released 28.05.2005 Test functions implemented for showing the counting results in as hex figure in the LCD when PD7 is pulled low 29.05.2005 Calculation formulas cleaned up and simplified, this solves minor display errors, especially for :64/:128 prescaler tested, works fine for all prescaler mode -> Version 1.1 released */ // --- Includefiles --- #include // Universal .h for AVR, does automatically load the device-specific // .h file, the device type is read from the makefile. #include // enables reading of data from the flash-memory #include // for usign string functions #include // standard input output functions // --- Prototypes for functions --- void init_lcd_4bit_interface(void); void update_lcd_4bit_interface(void); void char2lcd_4bit_interface(unsigned char lcdchar); void put_result_to_lcd(unsigned long cnt_result); void switch_to_next_mode(void); unsigned char asc2lcd(unsigned char asc_char); void pause(unsigned int n); void hex_output(unsigned long int number); unsigned char hex2asc(unsigned char hexbyte); // --- modes for different prescalers are --- #define PRESCALE_FACTOR_1 0 // 0 = no prescaler #define PRESCALE_FACTOR_64 1 // 1 = divide by 64 prescaler #define PRESCALE_FACTOR_128 2 // 2 = divide by 128 prescaler #define PRESCALE_FACTOR_640 3 // 3 = divide by 640 prescaler #define PRESCALE_FACTOR_1000 4 // 4 = divide by 1000 prescaler #define MAX_PRESCALE_MODE 4 // --- Global varialbles --- unsigned char videoram[33]; // 32 bytes for the lcd videoram (+1 for \n) as global variable unsigned char mode=PRESCALE_FACTOR_1; // default mode is: no prescaler // --- Constant Data that is kept in the flash memory --- unsigned char PROGMEM scr_greeting[]= "FrequencycounterVer 1.1 DL5NEG"; unsigned char PROGMEM scr_counting[]= " xx.xxx.xx MHz :1 DL5NEG"; // --- Port Definitions --- #define LCD_CMD_PORT PORTD // LCD command lines are connected to Port D #define LCD_CMD_DIR DDRD #define LCD_STR _BV(5) // PD5 is LCD strobe #define LCD_RS _BV(6) // PD6 is LCD register select #define LCD_DATA_PORT PORTB // LCD data lines are connected to PORT B #define LCD_DATA_DIR DDRB #define CNTR_PORT PORTD // Control port for the external counter is Port D #define CNTR_DIR DDRD #define CNTR_IN PIND #define CNTR_GATE _BV(4) // PD4 is gate signal input #define CNTR_RESET _BV(2) // PD2 is reset output #define CNT_DATA_IN PINC // Parallel output pins from external counter // are connected to Port C #define CNT_T1_IN PINB // PB1 is the physical pin for T1 #define CNT_T1_BIT 1 #define KEY_PORT PORTD // User keys are connected to PORTD #define KEY_IN PIND #define KEY_MODE_SEL _BV(3) // PD3 is mode select key #define KEY_DEBUG _BV(7) // PD7 to be pulled low for debug mode //;------------------------ here we go -------------------------- int main(void) { unsigned long int cnt_result; unsigned char ls_byte; unsigned int tmp_cntlb; unsigned int tmp_cnthb; TCCR1B = _BV(CS12) | _BV(CS11) ; // 16bit counter on, input is T1, falling edges, no prescaling CNTR_DIR |= CNTR_RESET; // set the reset pin to the external counter as output LCD_DATA_DIR = 0xF0; // the 4 higher pins as output for the LCD data bits LCD_CMD_DIR |= ( LCD_STR | LCD_RS ); // set LCD reg-sel. and strobe as output KEY_PORT |= KEY_MODE_SEL; // switch on the internal pull up resistor for the mode select key KEY_PORT |= KEY_DEBUG; // switch on the internal pull up resistor for the debug select pin init_lcd_4bit_interface(); // initialize the 2x16 char display strcpy_P( videoram, scr_greeting ); // copy the switch-on message to the videoram update_lcd_4bit_interface(); // transfer data from video ram to lcd display pause(2000); // show switch-on message for 2 seconds strcpy_P( videoram, scr_counting ); // copy the normal counting screen to the videoram update_lcd_4bit_interface(); // transfer data from video ram to lcd display for(;;) { // now keep counting until the gate closes // we detect the falling edge of the gateing-signal while( !(CNTR_IN & CNTR_GATE) ); // wait until gate is open while( CNTR_IN & CNTR_GATE ); // wait until gate closes // 1ms pause to make sure all signals are stable // (we have 128ms until the gate opens again) pause(1); // ----- read out the external 8bit counter value ----- // the MSB is directly connected to the T1 pin and must be mapped together // with the lower 7 bits which are connected to an input port ls_byte = ( CNT_T1_IN & _BV(CNT_T1_BIT) ) << (7-CNT_T1_BIT); // take T1 shifted to MSB ls_byte |= CNT_DATA_IN & 0x7F; // add the other 7 bits // ----- read the value of the internal 16bit counter ----- // (it is important to overtake the values into UNSIGNEDinteger // variables, otherwise the leftshift will give wrong results) tmp_cntlb = TCNT1L; tmp_cnthb = TCNT1H; // put together the 3 counter bytes (2 from the internal 16bit counter and // one from the external counter) to one 24 bit number cnt_result = tmp_cnthb; // value must be stored in a long variable before cnt_result <<= 16; // the 16bit shift can be done cnt_result += (tmp_cntlb << 8); // now add the lower byte of the internal cnt. cnt_result += ls_byte; // and add the value of the external cnt. // ---- if debug pin is pulled low, update counting result as hex figure in LCD ---- if( (KEY_IN & KEY_DEBUG)==0 ) hex_output(cnt_result); // ----- calculate frequency with selected prescaler and put result to LCD ----- put_result_to_lcd(cnt_result); // ----- reset the external counter ----- CNTR_PORT |= CNTR_RESET; CNTR_PORT &= ~CNTR_RESET; // It is important that the external counter is reset first, before // the internal counter is reset. Otherwise it can happen (if the // MSB of the external counter was set before the reset) that a falling // edge occurs for the internal counter and the result becomes one // internal counter bit to high!!! // ----- reset the internal counter ----- // set counter (low and higbyte) back to zero for the next gate-cycle // (highbyte must be written first, then the lowbyte must be written) TCNT1H = 0; TCNT1L = 0; // ----- switch to next prescaler mode if key was pressed ----- if( (KEY_IN & KEY_MODE_SEL)==0 ) switch_to_next_mode(); // now the counter is ready for the next gate-cycle, lets go up again } return(0); // to avoid a compiler warning } // ------------------------ init LCD --------------------------- void init_lcd_4bit_interface(void) { unsigned char initcnt; pause(15); // wait, datasheet req. at least 15ms LCD_CMD_PORT &= ~( LCD_STR | LCD_RS ); // strobe and reg-sel to low // according to datasheet the init-byte must be clocked in 3 times // (Register Select must stay low to indicate an instruction) for( initcnt=1 ; initcnt<=3 ; initcnt++ ) { char2lcd_4bit_interface(48); // value given in datasheet for init pause(5); // wait 5ms } char2lcd_4bit_interface( _BV(5) ); // switch to 4bit mode pause(5); char2lcd_4bit_interface( _BV(5) ); // set 2 lines, font 5x7 char2lcd_4bit_interface( _BV(7) ); pause(5); char2lcd_4bit_interface( 0 ); // display clear char2lcd_4bit_interface( _BV(4) ); pause(5); char2lcd_4bit_interface( 0 ); // entry mode incremental char2lcd_4bit_interface( _BV(6) | _BV(5) ); pause(5); char2lcd_4bit_interface( 0 ); // display on char2lcd_4bit_interface( _BV(7) | _BV(6) ); pause(5); } // ----------------------- update LCD --------------------------- void update_lcd_4bit_interface() { unsigned char lcdpos; LCD_CMD_PORT &= ~LCD_RS; // reg-sel low -> instr. char2lcd_4bit_interface(0x80); //set cursor to line1 (coloum1) char2lcd_4bit_interface(0x00); pause(15); //cursor setting requires 15ms pause LCD_CMD_PORT |= LCD_RS; // set reg sel high to indicate data, not instruction for( lcdpos = 0 ; lcdpos<16 ; lcdpos++ ) // write the 16 characters of line 1 { char2lcd_4bit_interface( ( (videoram[lcdpos] ) & 0xF0 ) ); // higher nibble first char2lcd_4bit_interface( ( (videoram[lcdpos]<<4) & 0xF0 ) ); // lower nibble last } // to come to line 2 we have to use and instruction to set the cursor to coloum 1 in line 2 LCD_CMD_PORT &= ~LCD_RS; // reg-sel low -> instr. char2lcd_4bit_interface(0xC0); //set cursor to line2 (coloum1) char2lcd_4bit_interface(0x00); pause(15); //cursor setting requires 15ms pause LCD_CMD_PORT |= LCD_RS; // set the reg select back to low to indicate data to come for( lcdpos = 16 ; lcdpos<32 ; lcdpos++ ) // write the 16 characters of line 2 { char2lcd_4bit_interface( ( (videoram[lcdpos] ) & 0xF0 ) ); // higher nibble first char2lcd_4bit_interface( ( (videoram[lcdpos]<<4) & 0xF0 ) ); // lower nibble last } } // ----------------------- character to LCD -------------------- // sends one byte to the LCD and takes the strobe high shortly // (depending on the reg-sel line this is recognized as character // or as instruction by the LCD. For some instructions additional // pauses may be necessary and must be cared for externally) void char2lcd_4bit_interface(unsigned char lcdchar) { LCD_DATA_PORT &= ~0xF0; // clear bits 4-7 LCD_DATA_PORT |= (lcdchar & 0xF0); // put data bits 4-7 to LCD port LCD_CMD_PORT |= LCD_STR; // send one strobe pulse to takeover the data LCD_CMD_PORT &= ~LCD_STR; pause(1); // do 1ms pause for the LCD } // --------- calculate the frequency from the counting result and put it to the LCD -------- // calculations are based on a gate-time of 128ms void put_result_to_lcd(unsigned long int cnt_result) { unsigned char res_string[20]; if( mode==PRESCALE_FACTOR_1 ) // for usage without prescaler { cnt_result *= 100; // calculate *100 :128 for cnt_result >>= 7; // 100Hz resolution at 128ms gate-time sprintf( res_string, "%8ld", cnt_result); // convert to decimal digits videoram[1] = res_string[0]; // put decimal digits to videoram videoram[2] = res_string[1]; videoram[3] = res_string[2]; videoram[5] = res_string[3]; videoram[6] = res_string[4]; videoram[7] = res_string[5]; videoram[9] = res_string[6]; videoram[10] = res_string[7]; } if( mode==PRESCALE_FACTOR_64 ) // for usage with :64 prescaler { // very little calculation necessary, prescaler of 128 would fit perfectly to a gate-time of 128ms, // for a prescaler of 64 we just have to do a divide by 2 for a resolution of 100kHz at 128ms gate-time cnt_result >>= 1; // :2 sprintf( res_string, "%8ld", cnt_result); // convert to decimal digits videoram[2] = res_string[1]; // put decimal digits to videoram videoram[4] = res_string[2]; videoram[5] = res_string[3]; videoram[6] = res_string[4]; videoram[8] = res_string[5]; videoram[9] = res_string[6]; videoram[10] = res_string[7]; } if( mode==PRESCALE_FACTOR_128 ) // for usage with :128 prescaler { // no calculation necessary, prescaler of 128 fits perfectly to a gate-time of 128ms // we get a resolution of 100kHz at 128ms gate-time sprintf( res_string, "%8ld", cnt_result); // convert to decimal digits videoram[2] = res_string[1]; // put decimal digits to videoram videoram[4] = res_string[2]; videoram[5] = res_string[3]; videoram[6] = res_string[4]; videoram[8] = res_string[5]; videoram[9] = res_string[6]; videoram[10] = res_string[7]; } if( mode==PRESCALE_FACTOR_640 ) // for usage with :640 prescaler { // for a prescaler of 640 we act like it was a prescaler of 64 (see above) and simply // arange the decimal digites shifted by one digit around the decimal point cnt_result >>= 1; // :2 sprintf( res_string, "%8ld", cnt_result); // convert to decimal digits videoram[1] = res_string[0]; // put decimal digits to videoram videoram[2] = res_string[1]; videoram[3] = res_string[2]; videoram[5] = res_string[3]; videoram[6] = res_string[4]; videoram[7] = res_string[5]; videoram[9] = res_string[6]; videoram[10] = res_string[7]; } if( mode==PRESCALE_FACTOR_1000 ) // for usage with :1000 prescaler { // for a prescaler of 1000 we act just like it was no prescaler at all and simply change // the displayed unit from MHz to GHz cnt_result *= 100; // *100 :128 cnt_result >>= 7; sprintf( res_string, "%8ld", cnt_result); // convert to decimal digits videoram[1] = res_string[0]; // put decimal digits to videoram videoram[2] = res_string[1]; videoram[3] = res_string[2]; videoram[5] = res_string[3]; videoram[6] = res_string[4]; videoram[7] = res_string[5]; videoram[9] = res_string[6]; videoram[10] = res_string[7]; } update_lcd_4bit_interface(); // transfer data from video ram to lcd display } //---------------------- switch to next mode ---------------------------------- // go to next prescaler mode and update the LCD screen mask acoordingly void switch_to_next_mode(void) { mode++; // switch to next prescale mode if( mode > MAX_PRESCALE_MODE ) // if last mode reached.. mode=0; // start with first mode again if( mode==PRESCALE_FACTOR_1 ) // for usage without prescaler { videoram[17]='1'; // write prescalefactor 1 to LCD videoram[18]=' '; videoram[19]=' '; videoram[20]=' '; videoram[12]='M'; // write M for MHz to frequency unit videoram[4]='.'; // set the 3-digit separation points videoram[8]='.'; } if( mode==PRESCALE_FACTOR_64 ) // for usage with :64 prescaler { videoram[17]='6'; // write prescalefactor 64 to LCD videoram[18]='4'; videoram[19]=' '; videoram[20]=' '; videoram[12]='G'; // write G for GHz to frequency unit videoram[3]='.'; // set the 3-digit separation points videoram[7]='.'; } if( mode==PRESCALE_FACTOR_128 ) // for usage with :128 prescaler { videoram[17]='1'; // write prescalefactor 128 to LCD videoram[18]='2'; videoram[19]='8'; videoram[20]=' '; videoram[12]='G'; // write G for MHz to frequency unit videoram[3]='.'; // set the 3-digit separation points videoram[7]='.'; } if( mode==PRESCALE_FACTOR_640 ) // for usage with :640 prescaler { videoram[17]='6'; // write prescalefactor 640 to LCD videoram[18]='4'; videoram[19]='0'; videoram[20]=' '; videoram[12]='G'; // write G for MHz to frequency unit videoram[4]='.'; // set the 3-digit separation points videoram[8]='.'; } if( mode==PRESCALE_FACTOR_1000 ) // for usage with :1000 prescaler { videoram[17]='1'; // write prescalefactor 1000 to LCD videoram[18]='0'; videoram[19]='0'; videoram[20]='0'; videoram[12]='G'; // write G for MHz to frequency unit videoram[4]='.'; // set the 3-digit separation points videoram[8]='.'; } pause(200); // pause to avoid unintended key repetitions } //-------------------------------------------- pause ----------------------------------------------------------- // waits for n times 1 ms (adapted for 4MHz crystal) void pause(unsigned int n) { unsigned int t; TCCR0 = 0x03; // set timer0 prescaler to 64 for( t=0; t>28 & 0x0000000F ); videoram[25]= hex2asc( number>>24 & 0x0000000F ); videoram[26]= hex2asc( number>>20 & 0x0000000F ); videoram[27]= hex2asc( number>>16 & 0x0000000F ); videoram[28]= hex2asc( number>>12 & 0x0000000F ); videoram[29]= hex2asc( number>>8 & 0x0000000F ); videoram[30]= hex2asc( number>>4 & 0x0000000F ); videoram[31]= hex2asc( number & 0x0000000F ); } //--------------------------- hex to asc -------------------------------------- // converts a hex value (00..0F) into the ASCII-character '0'..'F' unsigned char hex2asc(unsigned char hexbyte) { hexbyte += 48; // ASCII code for 0-9 is 48-57 if(hexbyte>=58) // ASCII code for A-F is 65-70 -> in that case add 7 hexbyte += 7; return hexbyte; }