Real Time Clock

[VRL_15]

How to implement a RTC without using any timer in PIC 16F887 ?

How to use DS1307 to achieve RTC for PIC?

 

[Wilksey]

A quick google search reveals an application note for just that:
**broken link removed**

Wilksey

 

[bryan]

In assembler straight from the Dallas web site.

**broken link removed**

 

[futz]

How to implement a RTC without using any timer in PIC 16F887 ?

How to use DS1307 to achieve RTC for PIC?

Yup, a DS1307 is a good way to do it. You'll need a DS1307, a 3V battery holder and battery off an old computer mainboard, three pullup resistors 4.7K to 10K, one 0.1uF ceramic cap, and a 32.768kHz crystal. Wire it up as shown in the datasheet and write some code. Or just buy a RTC module with all that stuff built for you (I'm using this one from Futurlec at present). The code isn't too terribly difficult, though it's a bit daunting at first. After you're immersed in it for a while you realize it's actually pretty simple.

Coincidentally I just happen to have finally decided to learn I2C last night, using one of the DS1307's I've had kicking around here for a long time. To learn it properly I'm writing my own code, and not using the MSSP module on the PIC 18F14K50 that I'm working with (at this point I consider that cheating). I have all my write code working well (the 1307's oscillator is working and it's outputting a 1Hz pulse on SQW/OUT that I have blinking an LED), but still have to tune up the read code. When that's done I'll post my newby code on my web-site.



I did run into one thing that wasted some time finding the problem. I was running the DS1307 at 3.3V. It "pretends" to work at that voltage, but when you write to it all it sends back are nacks (negative acknowledge). I finally read the datasheet more carefully and found that it won't work right at 3.3V. Powered it with 5V and all the nacks turned to acks - my code had been correct all along. I'd have wasted more time if I didn't have a analyzer to show me what was happening with my pulses - I love that thing!

The source code I found most helpful (borrowed from it a bit ) was Mike Pearce's I2C Routines, posted on Microchip's site.

 

[blueroomelectronics]

Futz, you could also reflash your Junebug with the Microchip Serial Analyzer firmware and you'd have an I2C bus sniffer.

 

[futz]

Futz, you could also reflash your Junebug with the Microchip Serial Analyzer firmware and you'd have an I2C bus sniffer.

Hey Bill. I could do that, but the Logic is so convenient that I just use it for everything. Best $150 I ever spent.