16F883 and Problems with HIGH statement

[aaanekre]

I started with PIC programming two days ago. The project is to make a tachometer for my car. I am using the pulsin statement and that is (finally) working as expected. I will use about 10 LED's to indicate the RPM. 800 RPM=1 LED, 1300 RPM=2 LED 1800RPM=3 LED etc.
The problem now is that when using the statement: HIGH PORTB.0 the port goes down again immidiately.. If I put a pause directly after it stays on however.
Is this normal??
My goal is that when the code enters the IF statement for say: 5000 RPM I want ALL the LED's "below" 5000RPM to be on.
Here is a copy of my code. I have removed some of the IF statements for better readability.


@ device pic16F883, INTRC_OSC_CLKOUT, BOD_OFF, PWRT_OFF, wdt_off, mclr_off, protect_off


'************************************************* ******************************
DEFINE OSC 8 'set OSC value to 8MHz for instructions PAUSE, PAUSEus and SOUND
'************************************************* ******************************

'************************************************* ******************************
'VARIABLES declaration
'IF VARIABLES USED FOUR COUNTER GO OVER 256, USE WORD INSTEAD

puls_h VAR Word 'input high
puls_l VAR Word 'input low
rpm var word
'************************************************* ******************************
'Setting registers

OSCCON = %01110001
ANSEL = %00000000 'choose digital i/o, val = 0
TRISA = %00000001 'set porta pins directions (1=input, high impedance)
TRISB = %00000000
PORTA = %00000000 'set port pins logic, A0 will be a default LOW with 100K WPD
PORTB = %00000000 'set port pins logic
'************************************************* ******************************

PAUSE 1000 'let the power level stabilize if not already done

start:

PULSIN PORTA.0, 0, puls_l
PULSIN PORTA.0, 1, puls_h
rpm = puls_l+puls_h

IF (rpm > 600 AND RPM < 2000) THEN
HIGH PORTB.0
'PAUSE 500 When I use this pause the LED will be lit 500ms here
LOW PORTB.1 'Without the pause the LED's flash fast and very dim.
LOW PORTB.2
LOW PORTB.3
GOTO START
endif
IF (rpm > 2000 AND RPM < 4000) THEN
HIGH PORTB.0
HIGH PORTB.1
'PAUSE 500 When I use this pause the LED will be lit 500ms here
LOW PORTB.2
LOW PORTB.3
GOTO START
endif
IF (rpm > 4000 AND RPM < 6000) THEN
HIGH PORTB.0
HIGH PORTB.1
HIGH PORTB.2
'pause 500 When I use this pause the LED will be lit 500ms here
LOW PORTB.3
GOTO START
endif
IF (rpm > 6000 AND RPM < 8000) THEN
HIGH PORTB.0
HIGH PORTB.1
HIGH PORTB.2
HIGH PORTB.3 'When this code is active, the LED on portb.3 is lit.
GOTO START
endif
GOTO START
END 'end of program

[Darrel Taylor]

The problem now is that when using the statement: HIGH PORTB.0 the port goes down again immidiately.. If I put a pause directly after it stays on however.
Is this normal??

Yes it is.

The 16F88x devices have analog functions on PORTB.

add this ...

ANSELH = 0

[aaanekre]

Thank you for helping me out with that one. Pretty simple problem now after reading about the ANSELH in the datasheet though... But its nice to get some help when you are banging the head...
I am learning new stuff all the time and I think the PIC processor is great. I work as a teacher in high school and we have been using Basic Stamp wich is a bit easier to work with but have limitations. (Especially the price !!) One of my students made code for a tachometer using BS2 and I promised him to port the program to a cheaper PIC processor. I managed to get the tachometer running now on a PIC16F628 that costs a fraction of the BS2. I hope my student will be pleased.
Thanks again.