For a previous project involving stepper motors, I wanted the microcontroller to remember exactly where the stepper motor was even after power loss. There wasn’t enough time to attempt it then, so I thought I’d try something similar now.
Here is the code :
// Written by Shane Ormonde 10th Feb 2014
#include
#include
#include
#pragma config FOSC=IRC,MCLRE=OFF,WDTEN=0,LVP=OFF,BOREN=OFF
//Functions
void setup(void);
void ee_write(char address, char data);
char ee_read(char address);
//Variables
int val = 1;
void main(void)
{
setup();
val = ee_read(0); // read eeprom address 0
if(val == 1) LATBbits.LATB7 = 1;
if(val == 2) LATCbits.LATC7 = 1;
if(val == 3) LATCbits.LATC6 = 1;
if(val == 4) LATCbits.LATC3 = 1;
val++; // increment val
if(val > 4) val = 1; // if val goes past 4, reset it
ee_write(0,val); // write the new val into address 0
while(1);
}
void setup(void)
{
OSCCON = 0b01100011; //internal oscillator block, 8MHz clock speed.
TRISC = 0b00000000;
TRISB = 0b00000000;
LATB = 0b00000000;
LATC = 0b00000000;
}
void ee_write(char address, char data)
{
EEADR = address;
EEDATA = data;
EECON1bits.WREN = 1; // enable eeprom write
EECON1bits.EEPGD = 0; //access data eeprom memory
EECON1bits.CFGS = 0; // access data eeprom memory (both bits must be cleared)
EECON2 = 0x55; // datasheet says to do this
EECON2 = 0xaa; // datasheet says to do this
EECON1bits.WR = 1 ; // start eeprom write
while( PIR2bits.EEIF == 0 ); // wait for the write to finish
PIR2bits.EEIF = 0; // reset the write finished flag
EECON1bits.WREN = 0; //disable eeprom writes
}
char ee_read(char address)
{
EEADR = address;
EECON1bits.EEPGD = 0; // access eeprom memory
EECON1bits.RD = 1; // eeprom read enable bit
return EEDATA;
}
Each time the PIC starts, it checks the value saved in EEPROM address 0. Depending on this value, it turns on one of four LEDs. Then the variable val is incremented by one and overwrites the previous value in EEPROM address zero. When the PIC is reset this process repeats.
The video is terrible quality so here is a pic of the circuit:
