Matrix Keypad and Sleep

[Razo]

Hi, I'm new and learning CCS.
I've got a project on the go which is giving me a headache. I'm using a PIC16f876A with a 4x4 matrix keypad connected to portb using internal pullup's using this driver http://www.ccsinfo.com/forum/viewtopic.php?t=28022&start=14. What I want to do is be able to send the pic to sleep if no button is pressed after a period of time (just before the sleep() command I will also send a pin low, which will be powering a LCD display) and then wake up if any of the buttons on the keypad is pressed.

I found a promising post which was posted 2 years ago http://www.ccsinfo.com/forum/viewtopic.php?t=29144 but the thread PCM points to is no longer here :(

If anyone could point me in the right direction I would be very grateful.

Thanks Raz

[PCM programmer]

You have two problems to solve.

1. How to create (presumably) a delay of several seconds, while not
blocking the keypad from entries during the delay ?

Answer: You could use a hardware timer. Configure it for a reasonably
long delay, that is an integral fraction of a second (to make things easy).
Then have a static counter variable inside the isr. Initialize it to 0 in
the declaration statement. Increment it once every timer interrupt.
Then check if it has counted up to the required number of interrupts
(say, 100 ms per interrupt x 100 interrupts = 10 second delay).
Then set a global flag to indicate this state. Pool the global flag in
a loop in main() that is also polling the keypad. When the flag is set,
disable the timer interrupts, clear the flag, and go to sleep.


2. How to wake-up from sleep upon a keypress ?

Answer: Use #int_rb interrupts.

In this thread, Ttelmah explains how to prepare to wake-up from
an int_rb interrupt, without having an #int_rb interrupt service routine.
In other words, you go to sleep, get a keypress, then wake-up and
resume executing the inline code that you were in, before you went
to sleep.
http://www.ccsinfo.com/forum/viewtopic.php?t=35940

[Razo]

Thanks PCM programmer.
Had to play with it a bit i.e. settings the row pins of the key pad to low.

Playing with the timer0 right now. but tbh I'm cheating ;). As I'm using a i2c RTC I'm talking to that during my main() loop and if a key isn't pressed for 30 sec's it then sleeps (which then powers down the RTC/LCD) and a push of a button gets it started again.

Going to get timer0 working as its the proper thing. But I'll do that another day

EDIT: Shifted the sleep timer over to timer0, had a few issues, but then again you never learn if it works the first time

Thx again for the pointers