What's the voltage on output pin when it's HIGH?

[mackrackit]

I am using 18F452, and reading portb.7.

It lights an LED the way it should, but I only read 1-2V.

With or with out the LED attached?

[keithdoxey]

With or with out the LED attached?

And if WITH the LED attached, did you also include a current limiting resistor in series with the LED ?

[TonyA]

And if WITH the LED attached, did you also include a current limiting resistor in series with the LED ?

I don't remember... I'll test again and re-post.

Thanks again,
T

[TonyA]

Yes, with the resistor and LED disconnected, I still read 2V out of the portb.7

'DEFINITIONS'
DEFINE OSC 20
DEFINE ADC_BITS 10        ' Set number of bits in result
DEFINE ADC_CLOCK 3
DEFINE ADC_SAMPLEUS 15

'PORT SETUP'
TRISA = %11111111       'set up all pins on portA as input pins
ADCON1 = %10000010      'Set PORTA analog conversion and right justify result

timeVar   var word
pauseTime var byte



main:

adcin 0, timeVar

pauseTime = timeVar / 12

high portb.7

pause pauseTime

low portb.7

pause pauseTime

goto main

I'm using the pic like this to provide a TTL pulse, (replacing a Schmitt trigger osc.). I had it hooked up in place of the Schmitt trigger and it works the way I expected, however I don't know why I only read 2V from my multi meter.

The Schmitt trigger's pulse read close to 5V.

[Ramonetnet]

I see no code saying "port b shall be used for output" .... do you ?
Ramon.

[TonyA]

I see no code saying "port b shall be used for output" .... do you ?
Ramon.

I was wondering about that too, but when you say "portb.7 HIGH", doesn't that automatically take care of that?

OR do you still have to define port b as output before the code?

Thanks,
T

[Ramonetnet]

a) instead of trying to imagine the possible combinations,
I would go and program it !

b) if you "select" Port A mode, why don't you specify the Port B mode of operation ?
It is NOT so large and difficult ...

c) if you say "HIGH PORTB.7" it means you write some data into the port,
not that you somehow are telling the compiler to configure it for you.

Let's do it and let's talk again. Ramon.