microchip程序实例-EEPROM.zip_DEMO_eeprom_microchip_microchip 示例

/** ******************************************************************* * Lesson 13 - "EEPROM" * * This lesson will provide code for writing and reading a single byte onto * the on-board EEPROM. EEPROM is non-volatile memory, meaning that it does * not lose its value when power is shut off. This is unlike RAM, which will * lose its value when no power is applied. The EEPROM is useful for storing * variables that must still be present during no power. * It is also convenient to use if the entire RAM space is used up. * Writes and reads to the EEPROM are practically instant and are much faster * than program memory operations. * Press the switch to save the LED state and then disconnect the power. When * power is then applied again, the program will start with that same LED lit. * When the lesson is first programmed, no LEDs will light up even with movement * of the POT. When the switch is pressed, the corresponding LED will be lit and * then the PIC will go to sleep until the switch is pressed again. Each press of * the switch saves the ADC value into EEPROM. The PIC uses interrupts to wake up * from sleep, take an ADC reading, save to EEPROM, and then goes back to sleep. * * PIC: 16F1829 * Compiler: XC8 v1.00 * IDE: MPLABX v1.10 * * Board: PICkit 3 Low Pin Count Demo Board * Date: 6.1.2012 * * ******************************************************************* * See Low Pin Count Demo Board User's Guide for Lesson Information* * ****************************************************************** */ #include <xc.h> //PIC hardware mapping #define _XTAL_FREQ 500000 //Used by the XC8 delay_ms(x) macro #define DOWN 0 #define UP 1 #define SWITCH PORTAbits.RA2 //config bits that are part-specific for the PIC16F1829 #pragma config FOSC=INTOSC, WDTE=OFF, PWRTE=OFF, MCLRE=OFF, CP=OFF, CPD=OFF, BOREN=ON, CLKOUTEN=OFF, IESO=OFF, FCMEN=OFF #pragma config WRT=OFF, PLLEN=OFF, STVREN=OFF, LVP=OFF /* -------------------LATC----------------- * Bit#: -7---6---5---4---3---2---1---0--- * LED: ---------------|DS4|DS3|DS2|DS1|- *----------------------------------------- */ unsigned char adc(void); //prototype void main(void) { OSCCON = 0b00111000; //500KHz clock speed TRISC = 0; //all LED pins are outputs LATC = 0; //init all LEDs OFF //setup switch (SW1) TRISAbits.TRISA2 = 1; //switch as input ANSELAbits.ANSA2 = 0; //digital switch //setup ADC TRISAbits.TRISA4 = 1; //Potentiamtor is connected to RA4...set as input ANSELAbits.ANSA4 = 1; //analog ADCON0 = 0b00001101; //select RA4 as source of ADC and enable the module (AN3) ADCON1 = 0b00010000; //left justified - FOSC/8 speed - Vref is Vdd //setup interrupt on change for the switch INTCONbits.IOCIE = 1; //enable interrupt on change global IOCANbits.IOCAN2 = 1; //when SW1 is pressed/released, enter the ISR INTCONbits.GIE = 1; //enable global interupts while (1) { LATC = eeprom_read(0x00); //load whatever is in EEPROM to the LATCH SLEEP(); //sleep until button is pressed } } unsigned char adc(void) { __delay_us(5); //wait for ADC charging cap to settle GO = 1; while (GO) continue; //wait for conversion to be finished return ADRESH; //grab the top 8 MSbs } void interrupt ISR(void) { unsigned char adc_value = 0; if (IOCAF) { //SW1 was just pressed IOCAF = 0; //must clear the flag in software __delay_ms(5); //debounce by waiting and seeing if still held down if (SWITCH == DOWN) { adc_value = adc(); //get the ADC value from the POT adc_value >>= 4; //save only the top 4 MSbs LATC = adc_value; //EEPROM is non-volatile, meaning that it can retain its value when no power is applied eeprom_write(0x00, adc_value); //save the value to EEPROM and go back to sleep } } }