Electronic – Suspected PIC alarm bug with RTCC module in PIC16LF series, cannot set alarm to 00 seconds

So thanks to the help of all here here's an alternative solution using the RTCC of the pic.

This solution makes much more sense then reading the time from an external SPI module.

you can buy a 32.768 crystal like this one: http://www.sparkfun.com/products/540

and two 11pf or 12 pf crystals and align them as shown on this schematic (top right): http://www.sparkfun.com/datasheets/DevTools/PIC/UBW32_MX795_v262.pdf

What I've still not figured out is how to power the RTC with an additional battery. If someone knows how I'd enjoy a post!

Here's a working example code:

// Master header file for all peripheral library includes
#include <plib.h>

// configuration settings
#pragma config FNOSC = PRIPLL, POSCMOD = HS, FPLLMUL = MUL_18, FPLLIDIV = DIV_2, FPBDIV = DIV_2, FPLLODIV = DIV_1
#pragma config FWDTEN = OFF

int main(void) {

    rtccTime    tm;          // time structure
    rtccDate    dt;          // date structure

    // Configure the device for maximum performance.
    // This macro sets flash wait states, PBCLK divider and DRM wait states based on the specified
    // clock frequency. It also turns on the cache mode if avaialble.
    // Based on the current frequency, the PBCLK divider will be set at 1:2. This knoweldge
    // is required to correctly set UART baud rate, timer reload value and other time sensitive
    // setting.
    SYSTEMConfigPerformance(72000000L);

    RtccInit();   // init the RTCC

    while(RtccGetClkStat()!=RTCC_CLK_ON);   // wait for the SOSC to be actually running and RTCC to have its clock source
                                            // could wait here at most 32ms

    RtccOpen(0x10073000, 0x07011602, 0);    // set time and date (- actually i don't know what time is set, but for the moment it doesn't matter.)
                                            // time is MSb: hour, min, sec, rsvd. date is MSb: year, mon, mday, wday.
                                            // please note that the rsvd field has to be 0 in the time field!

    RtccGetTimeDate(&tm, &dt);              // get current time

    DDPCONbits.JTAGEN = 0; // disable JTAGport, free up PORTA
    TRISA = 0b0000000000000000;
    TRISB = 0b0000000000000000;

    while(1){

        RtccGetTimeDate(&tm, &dt);

        // test: minutes odd or even
        int minutes = tm.sec%2;
        switch(minutes){
            case 0:
                PORTA = 0b0000000000000000;
                PORTB = 0b1111111111111111;
                break;
            case 1:
                PORTA = 0b1111111111111111;
                PORTB = 0b0000000000000000;
                PORTA._RA0 = 0;

                break;
        }
    }
}

I haven't used the part in a while, but it should be just a case of setting the configuration bits correctly. You don't say what compiler you are using so I can't give a code example, but your compiler manual should let you know (the commands will probably be at the end of the include file)

Also, you are better off reading the 30F family reference manual (Section 7 is the Oscillator) as it's far more detailed than the datasheet.

If you let us know which compiler and maybe post the code you have already tried it would help give a more specific answer (e.g. a code example)

I notice in the table below the FPR bits are dashed out for the FRC without PLLoption, even though note 1 says the pin function is dependent on these bits (if so, how should they be set?) This seems suspicious, I think I would raise a support ticket with Microchip to see what they have to say on the matter.