LABX-USB using port B problems

Hi,

I am having trouble using port B on the ME Labs LABX USB proto board.

I have connected a rotary encoder to port B3, 4, & 5. 4 is the common, set high to give me a supply, 3, & 5 the signals.
I want to detect the signals on 3, & 5. I have also set B0 to an input so that when I push on the encoder SW1 is pressed. I am getting very strange results.

Code:

---

Define OSC 48              'PIC18F4550
adcon1 = %00001111      'All digital
INTCON2.7 = 1        ' disable PORTB pull-ups
trisb = 0                ' portb all outputs
portb = 0              'all low
@ clrf UTRDIS
@ clrf UPUEN
led1        var portd.0
sw1        var portb.0
encsupply  var portb.4
encup      var portb.3
encdn      var portb.5

high encsupply
input encup
input encdn
input led1

start:
if sw1 = 0 then low led1
if sw1 = 1 then high led1
goto start
End

---

When I push the switch the led will light, but it will not go off unless I press button 2, 3, or 4. Also if I turn the encoder the led lights a little each detent, and even stranger if I have my fingers near to the switches or LED 1 I can vary the brightness of the LED, until it seems to go hard on, and once again can only be extinguished by pressing one of the 3 switches.

Can anyone help?

Regards
Bob...

The line input led1 is actually input sw1

Is SW1 the SW1 on the LAB-XUSB board? (the matrix keypad)

If so, then you need to turn ON the internal pull-ups on PORTB.
And PORTB.4 is the input. Set PORTB.0 LOW.

See the keypad pinouts in the LAB-XUSB schematic ... http://melabs.com/downloads/LABXUSCH_06.PDF

Hi Darrel,

Yes it is that switch. The idea was to have pull-ups off, use portb.4 as the supply, b3, & b5 as the encoder inputs, with the 100k weak pull-down resistors, and sw1 as the input when I push on the encoder shaft. I can't see why this does not work with the pull ups off.

Oh well, back to the drawing board. Thanks.

Bob.

RB0 doesn't have a 100k pull-down resistor, only RB3 and RB5 do.

Maybe I need to add a pull down to B0 too, though I still cant explain the strange results I was getting.
Anyway thank you for your help, I'll have another go at the weekend.
Hope I can get it to work, I love how fitting an encoder to the board made it an encoder with push button switch underneath, so just pushing the knob gives me an encoder with a switch, totally by accident, not design.

Amazing, & puzzling how I can write a USB interface, write the visual basic program to connect the hardware to flight simulator, and then I cant even get a switch to work.

By the way much kudos, & many thanks for your interrupt routines, they made a project at work really easy for me.

Kind regards
Bob...