PIC18F14K50 and i2cread/i2cwrite on PORT C

I am trying to use i2cread and i2cwrite on a PIC18F14K50.
PORTC.6 = Clock, PORTC.7 = Data.
Of course I know that there is an issue with the comparator/analog in settings.
So I am using:

ANSEL = 0
ANSELH = 0

to configure PORTC for digital I/O.
But i get the impression that this is not good enough...
When I measure the voltage on the clock pin (C6), it is low but can easily be pulled high with a resistor connected between PORTC.6 and +5V, giving me the impression that this pin is not configured as a digital output.
Am I still missing something?
(I prefer PORTC.6 and PORTC.7 because this would make the PCB design easier...)

Mmm... To eliminate things, I tried to use i2cread/i2cwrite on PORTB.4 (Clock) and PORTB.5 (Data), but this also doesn't seem to work.
TRISB=0 sets the outputs to a solid low level, but the I2C commands are still not working.

You need those pull-up resistors on both pins for I2C.
2.2 or 4.7K.

Quote:

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Originally Posted by Darrel Taylor

You need those pull-up resistors on both pins for I2C.
2.2 or 4.7K.

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Yes, I know that this is an often made mistake.
But of course I have those pull-up resistors connected!
The strange thing is that everything worked fine with a PIC18F4550, but not with a PIC 18F14K50.
When I look with an oscilloscope on the data and clock lines, I don't see any signal at all while sending an I2C command.

Quote:

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Originally Posted by RuudNL

TRISB=0 sets the outputs to a solid low level, but the I2C commands are still not working.

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Don't do that.
I2C requires the pins to be in INPUT mode when not transfering data.
The pins are never driven high, only low, which is why you need the pull-up resistors.

Since it's a 14K50, you're probably running at 48Mhz.
So you may want to add ...

DEFINE I2C_SLOW 1

Depending on if the device you're talking to is a 100Khz I2C part.
If it's a 400Khz part, you won't need it.

I know...
The only reason I tried TRISB=0 is because I wanted to check if I could use the pins as a digital output.
In the meantime I found the problem. In fact, it had nothing to do with the i2cread/i2cwrite commands.
The crystal I used apparently had a low activity. Sometimes the oscillator was working, but most of the time it was not!
I changed the crystal and now it works! (Maybe changing the values of the capacitors would have worked, but I did not try that.)