Real time clocks, out of the question?

[Astronouth7303]

Setting up just a realtime clock isn't that hard. I was thinking of doing it myself. I just have to figure out how to configure which timer to achieve something reasonable.

[Mike Bortfeldt]

Here is the code we used for a "clock". It uses Timer 2 and has a number of options for flexibility. It is not a "real time clock" in the sense that it doesn't compute hour/minute/second but works off clock "ticks", which for a 2 minute match, or a 15 second autonomous, works fine for us. By default, it's configured to count milliseconds (1 tick = 1 millisecond), but has 2 other predefined options for increased accuracy.

Mike

[Mark McLeod]

In teaching timers I use a demonstration program to calculate all the possible timer prescaler/postscaler combinations for a given Hertz or time period. It's an easy beginner exercise to write such a program for the PIC (or VB), and also can be used to teach them about maintaining the Master processor communication leading to an easy elimination of the Master handshake.

Here's a sample output calculating 2400 Hz used with an LCD display off a digital output.