PIC18F452 and RTC(DS1307) not working via I2C - Page 1
Forum section: electronics / general

author: diegoterc3
author_rank: Regular Contributor
timestamp: February 24, 2014, 03:22:28 pm
content: Hello I am using XC8 to work with an RTC but for some reason I can´t get it to work here is my code.//Beggining of code#include <xc.h>#include <pic18f452.h>#include <plib/i2c.h>#include <plib/pwm.h>#include <plib/timers.h>// CONFIG1H#pragma config OSC = XT // Oscillator Selection bits (XT oscillator)#pragma config OSCS = OFF // Oscillator System Clock Switch Enable bit (Oscillator system clock switch option is disabled (main oscillator is source))// CONFIG2L#pragma config PWRT = OFF // Power-up Timer Enable bit (PWRT disabled)#pragma config BOR = ON // Brown-out Reset Enable bit (Brown-out Reset enabled)#pragma config BORV = 20 // Brown-out Reset Voltage bits (VBOR set to 2.0V)// CONFIG2H#pragma config WDT = OFF // Watchdog Timer Enable bit (WDT disabled (control is placed on the SWDTEN bit))#pragma config WDTPS = 128 // Watchdog Timer Postscale Select bits (1:128)// CONFIG3H#pragma config CCP2MUX = ON // CCP2 Mux bit (CCP2 input/output is multiplexed with RC1)// CONFIG4L#pragma config STVR = ON // Stack Full/Underflow Reset Enable bit (Stack Full/Underflow will cause RESET)#pragma config LVP = OFF // Low Voltage ICSP Enable bit (Low Voltage ICSP disabled)// CONFIG5L#pragma config CP0 = OFF // Code Protection bit (Block 0 (000200-001FFFh) not code protected)#pragma config CP1 = OFF // Code Protection bit (Block 1 (002000-003FFFh) not code protected)#pragma config CP2 = OFF // Code Protection bit (Block 2 (004000-005FFFh) not code protected)#pragma config CP3 = OFF // Code Protection bit (Block 3 (006000-007FFFh) not code protected)// CONFIG5H#pragma config CPB = OFF // Boot Block Code Protection bit (Boot Block (000000-0001FFh) not code protected)#pragma config CPD = OFF // Data EEPROM Code Protection bit (Data EEPROM not code protected)// CONFIG6L#pragma config WRT0 = OFF // Write Protection bit (Block 0 (000200-001FFFh) not write protected)#pragma config WRT1 = OFF // Write Protection bit (Block 1 (002000-003FFFh) not write protected)#pragma config WRT2 = OFF // Write Protection bit (Block 2 (004000-005FFFh) not write protected)#pragma config WRT3 = OFF // Write Protection bit (Block 3 (006000-007FFFh) not write protected)// CONFIG6H#pragma config WRTC = OFF // Configuration Register Write Protection bit (Configuration registers (300000-3000FFh) not write protected)#pragma config WRTB = OFF // Boot Block Write Protection bit (Boot Block (000000-0001FFh) not write protected)#pragma config WRTD = OFF // Data EEPROM Write Protection bit (Data EEPROM not write protected)// CONFIG7L#pragma config EBTR0 = OFF // Table Read Protection bit (Block 0 (000200-001FFFh) not protected from Table Reads executed in other blocks)#pragma config EBTR1 = OFF // Table Read Protection bit (Block 1 (002000-003FFFh) not protected from Table Reads executed in other blocks)#pragma config EBTR2 = OFF // Table Read Protection bit (Block 2 (004000-005FFFh) not protected from Table Reads executed in other blocks)#pragma config EBTR3 = OFF // Table Read Protection bit (Block 3 (006000-007FFFh) not protected from Table Reads executed in other blocks)// CONFIG7H#pragma config EBTRB = OFF // Boot Block Table Read Protection bit (Boot Block (000000-0001FFh) not protected from Table Reads executed in other blocks)#define __CRYSTAL_4000000void main (void){unsigned char a=0;TRISB=0x00;TRISC=0xFF;PORTB=0;SSPADD=9; //FOSC/(4*(x+1))=Frecuencia de I2COpenI2C(MASTER,SLEW_OFF);OpenTimer2(TIMER_INT_OFF & T2_PS_1_1 & T2_POST_1_1);OpenPWM1(0);SetDCPWM1(1);StartI2C();putcI2C(0b11010000);putcI2C(0x00);putcI2C(0b0011010);putcI2C(0x00);putcI2C(0x00);putcI2C(0x00);putcI2C(0x00);putcI2C(0x00);putcI2C(0x00);putcI2C(0b00010000);StopI2C();while(1){}}// End of codeI just configure the PWM to see if the FOSC is the right one, which it is.I have attached an image which shows the communication between the pic and I2C with an oscilloscope.The main objective is to get the 1Hz of the SQW pin, and for some reason I can´t get it to work.I´ve noticed that the putcI2C(); command doesn´t test for and acknowledgment condition and tryied putting while(!PIR1bits.SSP1IF); after each putcI2C(); command but it also doesn´t work.In the oscilloscope I´ve noticed that the ack condition shows SDA = 1 and SCL = 1 but should{t it be SDA = 0 and SCL = 1?.has anyone encontered this kind of problem? The pull up resistors are 4.7K and the RTC is really close to the pic.Please someone help!

author: Unknown
author_rank: Unknown
timestamp: March 03, 2014, 07:54:06 pm
content: Quote from: diegoterc3 on February 24, 2014, 03:22:28 pmHi, you sure that is right? according to the datasheet "Illogical time and date entries result in undefined operation" and it looks like you're writing 0's into registers that shouldn't be set to 0. for example register 03h, day of the week, valid entries are 1-7 ?Also looking at the datasheet on power-up it seems to reset itself; so if you were to wait, then you only need to set reg 07h to get the 1hz output ?

author: diegoterc3
author_rank: Regular Contributor
timestamp: March 04, 2014, 10:42:09 pm
content: Hello I got it working.As you say those registers aren´t supposed to carry those numbers, but you can still write in them. It just doesn´t make sense to have a 0 DOW or something like that.My problem solution was that after each putI2C(); I have to put a IdleI2C(); just to wait until each write command has finished.There is a note on the microcontroller peripheal that says that if one does not put that wait until idle the microcontroller will flip out and try to do all the commands without finishing the communication with the last one.Also I had the SDA and SCL lines backwars. =PBut yeah if anyone has any trouble with I2C you can send me a mail.

author: Unknown
author_rank: Unknown
timestamp: March 05, 2014, 06:51:41 pm
content: lol - you gotta love electronics; being 99.8% there sometimes isn't enough!cool! glad you got it sorted! ;-)