Hi,

I'm designing a controller board for a CD PLAYER.
The controller is based around a PIC18F452.

I'm wondering whether I need to use interrupts or not.

To sum up, while playing (or not), the PIC could received instructions from a RC5 remote control or a switch board (buttons PLAY, STOP, SKIP FWD, ...)

Do I need to use interrupts to check whether a switch or a RC5 code is received by the PIC ?

Or do I include two Functions in the main loop that checks every 20ms if some RC5 code is reveived or some button is pressed.

I'm developping the code ic C.

Could be something like this

Code:

void main(void)
{
  InitializeControler();
  while(1)
  {
    detectButtons(); //detect if a buttons is pressed
    detectIRCode(); //detect if a RC5 code is recevied    
    waitFor(20); //delay of 20ms
  }
}

thanks for your help

Regards

Originally Posted by ZERS

Hi,

I'm designing a controller board for a CD PLAYER.
The controller is based around a PIC18F452.

I'm wondering whether I need to use interrupts or not.

To sum up, while playing (or not), the PIC could received instructions from a RC5 remote control or a switch board (buttons PLAY, STOP, SKIP FWD, ...)

Do I need to use interrupts to check whether a switch or a RC5 code is received by the PIC ?

Or do I include two Functions in the main loop that checks every 20ms if some RC5 code is reveived or some button is pressed.

You can do it either way, it's mostly personal preference, although there are sometimes circumstances where you HAVE to use interrupts.

Useing interrupts is generaly a faster and more relyable solution. If you use normal checking in software, let's say every 20ms, you might miss an event... Integrating interrupts into your existing code is easy, no need to wory...

Originally Posted by Jay.slovak

Useing interrupts is generaly a faster and more relyable solution. If you use normal checking in software, let's say every 20ms, you might miss an event... Integrating interrupts into your existing code is easy, no need to wory...

Could you please give me an example ?

I do not understand how deal with the timer while using interrupts, more precisely while there are two sources of interrupts...

One source using A/D conversion (the switches board), the other one the RC5 codes

If you use multiple sources for interrupt, you need to add checking of Flag Bits. You should check T0IF & ADIF flag bits.... and then execute correct interrupt routine. Yes, there is a chance that you will get A/D interrupt and Timer interrupt at the same time, If you use PIC18 series, you can use priority levels to solve this issue..

Originally Posted by Jay.slovak

If you use multiple sources for interrupt, you need to add checking of Flag Bits. You should check T0IF & ADIF flag bits.... and then execute correct interrupt routine. Yes, there is a chance that you will get A/D interrupt and Timer interrupt at the same time, If you use PIC18 series, you can use priority levels to solve this issue..

After reading the datasheet, it seems that I will set the "A/D" conversion in high priority and the RC5 in low priority.

Still after reading the datasheet, It might be interesting to use the Timer Interrupts (reading the timer value to check if the PIC is stiuck), thus introducing a third source of interrupt.

Is it possible ?

Originally Posted by ZERS

Originally Posted by Jay.slovak

If you use multiple sources for interrupt, you need to add checking of Flag Bits. You should check T0IF & ADIF flag bits.... and then execute correct interrupt routine. Yes, there is a chance that you will get A/D interrupt and Timer interrupt at the same time, If you use PIC18 series, you can use priority levels to solve this issue..

After reading the datasheet, it seems that I will set the "A/D" conversion in high priority and the RC5 in low priority.

Still after reading the datasheet, It might be interesting to use the Timer Interrupts (reading the timer value to check if the PIC is stiuck), thus introducing a third source of interrupt.

Is it possible ?

Are you trying to detect when the PIC is stuck? Theres a feauture call WDT watchdog timer.... that might be more usefull.

Originally Posted by Jay.slovak

Are you trying to detect when the PIC is stuck? Theres a feauture call WDT watchdog timer.... that might be more usefull.

Yes, especially while testing the program.
I've never seen any program without a bug, especially developped by me :wink: :lol:

Do I need to use interrupts to check whether a switch or a RC5 code is received by the PIC ?

Using interrupts for switch detection would make it prone to switch bounce. Switch debounce software will totally negate using interrupts for switches in the first place. In general, switch events are so slow, polling offers a natural debounce. A user will not notice any sluggishness even if you poll switches once every 50-100ms.

IR remote sensors are in the gray area where polling or interrupts can be used. I have used a polling method on a karaoke machine with an IR remote sensor, LED displays, pushbuttons, etc. It used an ancient PIC16C57 @4Mhz but was fast enough to poll the IR sensor every 256usec. This chip had no interrupts so I had no choice but to poll.