Strange behaviour of my PBP code.

I have a strange "bug" in my PBP program that I can´t understand.

I have taken out the code that contains the bug from my bigger program and run it on two different PIC´s on two different devboards and the bug is still there so it must have something with the software to do.

The code lets you to select number of shooters (1-5), if Shooters = 2 the Status_LED will blink 2 times and then delay for a longer time before the next two blink.

You change the Shooters value by pressing SW_Forward or SW_Reverse, SW_Launch will start the rest of the program (not included) with the number of shooters stored in the variable Shooters.

The code works pretty well until yesterday when I tried to press the SW_Forward button for about 10 - 15 times as fast that I could then the program hangs and the Status_LED is constantly on, it looks like the program goes into a never ending loop and I must Reset the PIC to continue. the same thing will happen if I press SW_Reverse as fast I can.

Well the program works, but I want to know why the program hangs when I press the SW_Forward or SW_Reverse buttons several times fast

Code:

<html> <head></head> <body><pre><code>Define OSC 8 Include "alldigital.pbp" ;DT´s All Digital Define SHOWDIGITAL 1 Asm ;=========================================================================== __CONFIG _CONFIG1L, _PLLDIV_5_1L & _CPUDIV_OSC1_PLL2_1L & _USBDIV_2_1L __CONFIG _CONFIG1H, _FOSC_HS_1H __CONFIG _CONFIG2H, _WDT_OFF_2H & _WDTPS_512_2H __CONFIG _CONFIG3H, _PBADEN_OFF_3H __CONFIG _CONFIG4L, _LVP_OFF_4L & _XINST_OFF_4L & 0DFh Endasm;------------------------------------------------------------------------- Shooters Var Byte i Var Byte Delayi Var Byte SW_Launch Var PORTA.0;======================================================= SW_Reverse Var PORTA.1 SW_Forward Var PORTA.2 Status_LED Var PORTC.0;------------------------------------------------------- Shooters = 2 ;Default value Main:;========================================================================== Gosub Delay2 For i = 1 To Shooters High Status_LED Gosub Delay1 Low Status_LED Gosub Delay1 Next i Goto Main;---------------------------------------------------------------------- Delay1:;======================================================================== For Delayi = 0 To 100 Pause 2 Gosub Check_Buttons Next Delayi Return Delay2: For Delayi = 0 To 255 Pause 5 Gosub Check_Buttons Next Delayi Return;------------------------------------------------------------------------- Check_Buttons:;================================================================= If SW_Launch = 0 Then High Status_LED Pause 50 While SW_Launch = 0: Wend Pause 50 ' goto start_new Endif If SW_Forward = 0 Then High Status_LED Pause 50 Shooters = Shooters + 1 If Shooters > 5 Then Shooters = 1 While SW_Forward = 0:Wend Pause 50 Low Status_LED Goto Main Endif If SW_Reverse = 0 Then High Status_LED Pause 50 Shooters = Shooters - 1 If Shooters < 1 Then Shooters = 5 While SW_Reverse = 0:Wend Pause 50 Low Status_LED Goto Main Endif Return;------------------------------------------------------------------------- </code></pre></body> </html>

Ok.. now I have tested with another PIC,a PIC16F887 and then it works, the "bug" is gone.
So why does it hang with a PIC18F2550, PIC184550, and 18F4520?

Does it have something with the config fuses to do? what have I missed?

Hi Fredrick,

In the Check_Buttons subroutine, there's 2 Goto Main statements.

You should use RETURN to exit a subroutine.

Using GOTO will cause the stack to overflow.
With 18F's a stack overflow can cause a Reset.

But with 16F's the stack just wraps around and seems to work, although it's probably not working 100%.

Ohh so simple!

When I notified the problem fist time I was saying to myself that this time I will try to solve the problem without help from anybody, so I have spent a lot off hours on trying to find the problem, but then I give up and started a thread here again.

Thank you Darrel.

But it´s OK to use Goto´s within the subroutine as long as I call a label that is in the subroutine and only leave the subroutine by doing a Return

Exactly!

You've got it now. http://www.picbasic.co.uk/forum/images/icons/icon14.gif

How is it with variables?
If I overflow a byte sized counter it will turn to 0 after passing 255, but is it OK to let a variable overflow? or should I take care of the overflow like this

Code:

IF Counter > 254 Then Counter = 0 Endif

For BYTE sized variables, when the value goes over 255 the upper bits are lost, which makes it automatically wrap around to 0.
You don't need to do it manually.

For words, it wraps when over 65535.