16f887 44 pin demo board code problem?

Hello,

I just got my new version of PBP 2.50 the other day and am trying to write a simple program to light LEDs using a PicKit 2 programmer on the demo board that came with my PICKIT 2 Debug Express. It's really strange that the LEDs do turn on/off on the demo board because the code to turn them on/off is inside an IF Push_Button = Is_Pressed THEN that expects a button press to turn them on/off and it runs the code, flashing the LEDs in the proper sequence without a button press? The other code inside the IF Push_Button = Is_Not_Pressed THEN doesn't turn the LEDs on/off when pressed? The push button has no effect in the code.

I wasn't sure how to set the internal oscillator but after reading the data sheet for the 16f887 it said: The Fail-Safe Clock Monitor is designed to detect a failure of the external clock source and switch automatically to the internal oscillator which it seems to have done because the LEDs are turning on/off. According to the data sheet the oscillator is running at 31 kHz and to select other frequencies I need to set the OSCCON register. Am I correct in thinking that for 4 MHz I would include in my program OSCCON %01100xxx, I'm not sure what bits 0, 1 and 2 would be set to? Could anyone give me some insight about these setting?

I checked and triple checked the schematics for the demo board to be certain that all my tris settings are correct for the LED's and for the on board push button and anything else that I could think of that could cause this but I must be missing something really simple, like when I thought I had ver 2.47 of PBP but instead had ver 2.45.....

Does anyone here see any obvious mistakes in my code below, any help would really be appreciated.

Thanks
jessey

Code:

' Name : Blink_Led.BAS ' Author : Jessey Montgomery ' Notice : ' : ' Date : 02/12/2008 ' Version : PicBasic Pro ver 2.50, MPASM v5.20, MicroCode ' Notes : Studio ver 3.0.0.5, PICKIT 2 programmer, 44 pin ' : PIC16F877-I/PT Microprocessor on PicKit 2 demo board. ; 2 ; P ; C ; 1 C ; A L P / ; D C C I ; K S S C C ; C / / / S ; / O I K A O ; X D D C 1 1 ; T S S S P T ; / / / / / / ; 6 5 4 3 2 1 0 3 2 1 ; C C C D D D D C C C C ; R R R R R R R R R R N ; ------------------------------- ; |* 4 4 4 4 4 3 3 3 3 35 34 | ; RC7/RX/DT<-->|1 4 3 2 1 0 9 8 7 6 33|<-->NC ; RD4<-->|2 32|<-->RC0/T1OSO/T1CKI ; RD5/P1B<-->|3 31|<---RA6/OSC2/CLKOUT ; RD6/P1C<-->|4 30|<---RA7/OSC1/CLKIN ; RD7/P1D<-->|5 29|<---VSS- ; -VSS<-->|6 PIC16F887 28|<---VDD+ ; +VDD--->|7 27|<-->RE2/AN7 ; RB0/AN12/INT<-->|8 26|<-->RE1/AN6 ; RB1/AN10/C12IN3-<-->|9 25|<-->RE0/AN5 ; RB2/AN8<-->|10 24|<-->RA5/AN4/SS/C2OUT ; RB3/AN9/PGM/C12IN2-<-->|11 2 3 4 5 6 7 8 9 0 23|<-->RA4/T0CKI/C1OUT ; | 1 1 1 1 1 1 1 1 2 21 22 | ; ------------------------------- ; C C 1 G K T P | 1 + + ; N N 1 1 L A P 0 N N N ; N T C D V N I I I ; A / P P / I 2 2 1 ; / 3 S S R 2 1 C C ; 4 1 C C L 1 C / / ; B N I I C C / F + ; R A / / M / 1 E F ; / 6 7 / U N R E ; 5 B B 3 W A V R ; B R R E P / C V ; R R L 1 / / ; U A | 3 ; / R F N ; O E A ; N R / ; A V 3 ; / / A ; 0 2 R ; A N ; R A ; / ; 2 ; A ; R Clear 'Set all ram registers to zero PORTA = 0 PORTB = 0 PORTC = 0 PORTD = 0 PORTE = 0 'VSS VDD MCLR Ect. Pins 'VDD '(pin 7) 'VDD '(pin 28) 'VSS '(pin 6) 'VSS '(pin 29) 'NOT USED '(pin 12) 'NOT USED '(pin 13) 'NOT USED '(pin 33) 'NOT USED '(pin 34) ' Set The TRIS In/Out Pins 'PORTA PINS TRISA.0 = 1 '(pin 19) NOT USED, VAR PORTA.0 TRISA.1 = 1 '(pin 20) NOT USED, VAR PORTA.1 TRISA.2 = 1 '(pin 21) NOT USED, VAR PORTA.2 TRISA.3 = 1 '(pin 22) NOT USED, VAR PORTA.3 TRISA.4 = 1 '(pin 23) NOT USED, VAR PORTA.4 TRISA.5 = 1 '(pin 24) NOT USED, VAR PORTA.5 TRISA.6 = 1 '(pin 31) NOT USED, VAR PORTA.6 TRISA.7 = 1 '(pin 30) NOT USED, VAR PORTA.7 'PORTB PINS TRISB.0 = 1 '(pin 8) Push_Button VAR PORTB.0 TRISB.1 = 1 '(pin 9) NOT USED, VAR PORTB.1 TRISB.2 = 1 '(pin 10) NOT USED, VAR PORTB.2 TRISB.3 = 1 '(pin 11) NOT USED, VAR PORTB.3 TRISB.4 = 1 '(pin 14) NOT USED, VAR PORTB.4 TRISB.5 = 1 '(pin 15) NOT USED, VAR PORTB.5 TRISB.6 = 1 '(pin 16) NOT USED, VAR PORTB.6 TRISB.7 = 1 '(pin 17) NOT USED, VAR PORTB.7 'PORTC PINS TRISC.0 = 1 '(pin 32) NOT USED, VAR PORTC.0 TRISC.1 = 1 '(pin 35) NOT USED, VAR PORTC.1 TRISC.2 = 1 '(pin 36) NOT USED, VAR PORTC.2 TRISC.3 = 1 '(pin 37) NOT USED, VAR PORTC.3 TRISC.4 = 1 '(pin 42) NOT USED, VAR PORTC.4 TRISC.5 = 1 '(pin 43) NOT USED, VAR PORTC.5 TRISC.6 = 1 '(pin 44) NOT USED, VAR PORTC.6 TRISC.7 = 1 '(pin 1) NOT USED, VAR PORTC.7 'PORTD PINS TRISD.0 = 0 '(pin 38) Led_1 VAR PORTD.0 TRISD.1 = 0 '(PIN 39) Led_2 VAR PORTD.1 TRISD.2 = 0 '(pin 40) Led_3 VAR PORTD.2 TRISD.3 = 0 '(pin 41) Led_4 VAR PORTD.3 TRISD.4 = 0 '(pin 2) Led_5 VAR PORTD.4 TRISD.5 = 0 '(pin 3) Led_6 VAR PORTD.5 TRISD.6 = 0 '(pin 4) Led_7 VAR PORTD.6 TRISD.7 = 0 '(pin 5) Led_8 VAR PORTD.7 'PORTE PINS TRISE.0 = 1 '(pin 25) NOT USED, VAR PORTE.0 TRISE.1 = 1 '(pin 26) NOT USED, VAR PORTE.1 TRISE.2 = 1 '(pin 27) NOT USED, VAR PORTE.2 TRISE.3 = 1 '(pin 18) NOT USED, VAR PORTE.3 @ __config _CONFIG1, _INTRC_OSC_CLKOUT & _WDT_ON & _MCLRE_ON & _LVP_OFF & _CP_OFF Push_Button VAR PORTB.0 '(pin 8) Led_1 VAR PORTD.0 '(pin 38) Led_2 VAR PORTD.1 '(PIN 39) Led_3 VAR PORTD.2 '(pin 40) Led_4 VAR PORTD.3 '(pin 41) Led_5 VAR PORTD.4 '(pin 2) Led_6 VAR PORTD.5 '(pin 3) Led_7 VAR PORTD.6 '(pin 4) Led_8 VAR PORTD.7 '(pin 5) a VAR BIT ' used in IF THEN's instead of GOTO's A = 0 Is_Pressed CON 0 Is_Not_Pressed CON 1 _On CON 1 _Off CON 0 IF a = 0 THEN MainLoop MainLoop: IF Push_Button = Is_Not_Pressed THEN PORTD.0 = 1 PORTD.1 = 1 PORTD.2 = 1 PORTD.3 = 1 PORTD.4 = 1 PORTD.5 = 1 PORTD.6 = 1 PORTD.7 = 1 pause 500 PORTD.0 = 0 PORTD.1 = 0 PORTD.2 = 0 PORTD.3 = 0 PORTD.4 = 0 PORTD.5 = 0 PORTD.6 = 0 PORTD.7 = 0 endif IF Push_Button = Is_Pressed THEN Led_1 = _On PAUSE 350 Led_1 = _Off Led_2 = _On PAUSE 350 Led_2 = _Off Led_3 = _On PAUSE 350 Led_3 = _Off Led_4 = _On PAUSE 350 Led_4 = _Off Led_5 = _On PAUSE 350 Led_5 = _Off Led_6 = _On PAUSE 350 Led_6 = _Off Led_7 = _On PAUSE 350 Led_7 = _Off Led_8 = _On PAUSE 350 Led_8 = _Off ENDIF pause 100 IF a = 0 THEN MainLoop END

Hi, Jessey

at first sight,

You also have to disable Comparators and declare ADC shared pins as digital ...

Alain

PS: PIC16F877-I/PT Microprocessor or 16 F 887 ???

My config line.

Code:

@__config _CONFIG1, _INTRC_OSC_NOCLKOUT & _WDT_ON & _MCLRE_OFF & _LVP_OFF & _CP_OFF

1 Attachment(s)

Quote:

Am I correct in thinking that for 4 MHz I would include in my program OSCCON %01100xxx, I'm not sure what bits 0, 1 and 2 would be set to?

Yes. OSCCON = %01100000 would set it to 4MHz. Bit 0 SCS allows you to switch from the osc set in config to internal. Bits 1, 2 and 3 are read only bits that indicate the oscillator status.

Look at the modified version of your example attached here for a few other comments. I haven't tested this, but it should help get you up & running.

Thanks Bruce, your the man!

Thanks Everyone,

Once again I proved to myself how (dumb) forgetful I am , I now remember the countless number of times I've read newbies asking why their programs won't work and the responses have always been to check the data sheets for the device your using for Comparators and such. I'll definitely be paying more attention to that the next time I use a new unfamiliar micro.

Hey Bruce, I really appreciate you laying out my program and explaining all the settings in your comments, it would have taken me forever to read and try to figure out the datasheet for all those settings not to mention additional posts. The program works great now but one thing I wanted to mention is that my 44 pin demo board doesn't have a crystal installed on the board even though it reflects that in the schematics, there are pads on the board for the crystal and related components but those pads are all un-populated. Even though the program worked good using _INTRC_OSC_NOCLKOUT I changed it to _INTRC_OSC_CLKOUT, am I right in doing that and also is there a way for me to verify that the program is running on 4 MHz without using an oscilloscope?

Thanks Again
jessey

Quote:

Originally Posted by jessey

Even though the program worked good using _INTRC_OSC_NOCLKOUT I changed it to _INTRC_OSC_CLKOUT, am I right in doing that

In CLKOUT mode you can send a clock pulse signal out to another device.
NOCLKOUT you can use the pins for I/Os

Quote:

and also is there a way for me to verify that the program is running on 4 MHz without using an oscilloscope?

Program a simple blinky with one LED that will blink at a certain rate. If you code has
DEFINE OSC 4
and the chip is running at 4MHz, then the LED will blink at the correct rate.

Thanks Dave,

I added the code below in the MainLoop to check out your explanation and I can see that the timing is correct at 4 MHz and runs twice as fast at 8 MHz, that's cool!

Code:

IF Push_Button = Is_Pressed THEN OSCCON = MHz8 ELSE OSCCON = MHz4 ENDIF

Thanks
jessey

Hello,
I was wondering if someone could suggest why this code below doesn't work to change the oscillator speed of the Internal Oscillator while the program is running but the other code block below does work? Another thing I was pondering is, shouldn't I be setting bit 0 of the OSCCON register to 1? The datasheet for the 16f887 says this about bit 0:
1 = Internal oscillator is used for system clock
0 = Clock source defined by FOSC<2:0> of the CONFIG1 register.

Code:

'this doesn't work IF Push_Button = Is_Pressed THEN IF OSCCON = %01100000 THEN OSCCON = %01110000 ELSE OSCCON = %01100000 ENDIF WHILE Push_Button = Is_Pressed PORTD = %10000001 ' Show that button press has stopped the code here WEND ENDIF

Code:

'this works IF Push_Button = Is_Pressed THEN IF B = 0 THEN B = 1 ELSE B = 0 ENDIF WHILE Push_Button = Is_Pressed PORTD = %10000001 ' Show that button press has stopped the code here WEND ENDIF IF B = 0 THEN OSCCON = %01110000 ' 8 MHz IF B = 1 THEN OSCCON = %01100000 ' 4 MHz

Thanks
jessey

hi,

I think it is "not so good" to change osc settings WHILE you touch the button ( debounce issue guaranteed !!! ...PORTD can show anything but truth !!! )

good reason for #2 to work better ... ONLY better.

I ( it's me ...) Would look for button state CHANGES instead of simply the button state ...

Alain

Quote:

Another thing I was pondering is, shouldn't I be setting bit 0 of the OSCCON register to 1? The datasheet for the 16f887 says this about bit 0:
1 = Internal oscillator is used for system clock
0 = Clock source defined by FOSC<2:0> of the CONFIG1 register.

See post #4
You have the OSC set for internal at the start. In the config settings. You do not need to change the source.