PCINT Interrupts how to use?

Paulvk · Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY

I want to use PCINT8 as an Interrupt but am having a hard time finding some sort of example on how to use these sort of Interrupts in Bascom I can find little bits but not a step by step example that explains it can any body point me to one.

albertsm · Joined: 09 Apr 2004 Posts: 6197 Location: Holland

did you checked the pcint_change.bas sample from the samples dir?

Paulvk · Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY

Did not see that! I have been going through the help trying to work it out I will have a look at the example and see if I can work it out thank you for the pointer (again!)

regards Paul

albertsm · Joined: 09 Apr 2004 Posts: 6197 Location: Holland

the sample shows 2 ways, it would be better to make an example for non interrupt based, and interrupt based.
maybe an enthusiast user can make better samples Smile

Paulvk · Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY

So looking at the example

Enable Interrupts 'enable global ints
Enable Pcint0 'we enable pcint0 as this has pcint0-pcint7

Then would
Enable Pcint1 cover pcint8-pcint15

Regards paul

Paulvk · Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY

When I get this hardware to work I will post the whole program. I am trying to respond to a DTMF decoder when it has a lock on a tone pair. As I can do this in a loop I will do it that way as an example but also want to do it as a jump due to an interrupt so that it does not slow things up. The reason for PCINT8 is that its spare on the board to be used.

albertsm · Joined: 09 Apr 2004 Posts: 6197 Location: Holland

Paulvk · Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY

Ok I have the pin change interrupt working (PCINT8) but how do I get it to respond only to a rising change ie logic 0 to 1 but not when it goes back 1 to 0 again.

hgrueneis · Joined: 04 Apr 2009 Posts: 906 Location: A-4786 Brunnenthal

You can not.
PCINT.... are only change interrupts and can not be configured.
If you need rising or falling then you need to use int0 or int1 for example.
The possibility you have with PCINT is to read the port pin on interrupt and determine the state of the input, so you can determine if this is the interrupt to perform the wanted action.You hopefuly masked the interrupt, otherwise you also get int's from the other pcints in that group (I did not read the sample).
See the AVR datasheets for external interrupts.
Hubert

Paulvk · Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY

Ok that confirms what I suspected after reading through the data sheets and bascom (a number of times) yes I have masked the interrupt, I did not use one of the normal interrupts as I did not want to make a total new artwork and did not know then that INT0, INT1 would be the best to use. It has taught me more though, I will also learn more as I work around the state changes and move on to the next problem I have given myself, how to swap around binary 0100 to 0010 as I have the 4 bits around the wrong way at least the hardware works it detects the DTMF and decodes it.

hgrueneis · Joined: 04 Apr 2009 Posts: 906 Location: A-4786 Brunnenthal

If you talk about input bits in a nibble, there are a few possibilities.
You can make a 16-byte conversiontable but the easiest maybe not most elegant is to declare 1 variable read the corresponding bitlocation and write the bit to the new location in the variable. An other mothode would be to AND, then shift and add also in extra variables 4 times ( a bit more time consuming).
Hubert

Paulvk · Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY

This has the interrupt working for a 0 to 1 transition and the bits I want are 1,2,3,4 as I used 0 as the pin change a re-do of the hardware would get rid of the mirror bits but what the heck I have learnt more this way.

Paulvk · Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY

Ok I have a working example of pin change interrupt this uses a VOIP ATA to enable remote control of some relays, it answers the call after a pre set number of rings then waits and decodes DTMF tones sent to it. This is the prototype made with 3 seperate boards I am now making a finished version on one board this code would show how to use the interrupts if mark wants he can use it to replace the example in bascom. Any improvements/comments are most welcome.

hgrueneis · Joined: 04 Apr 2009 Posts: 906 Location: A-4786 Brunnenthal

The ENABLE INTERRUPTS would normaly be the last thing after all the setup.
I would also not spend so much time in the ISR routines because as long as you are in the ISR no other interrupt is serviced with atmega.
This might not be a problem with your specific application but it is not a good practice in general.
Interrupts should only set a condition and then you do the evaluation from the main routine possibly in a sub.
If you have 4 pins that can change then you could use all four interrupts and branch in the main program after reading the port and AND with an "ON VALUE" or "CASE".
Just some thoughts
Hubert

Paulvk · Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY

All information is welcome, the events that trigger the interrupts are hardware events one is when the DTMF chip has valid tone pairs the other is when the ATA puts ring on the line, it could have been done in a loop but I wanted to teach myself how to use the interrupts. I do understand that spending as short a time in the interrupt as possible is the best way but want I wanted to do was to have a program that runs but do something else when hardware events happen then go back to where it was and keep running. The project has served its purpose well it has and still is teaching me a lot plus I will have a usefull bit of harware to control devices with. When its finnished I will make both the code and hardware plans avaliable for all.