One wire stops working when clock increased

[smanzer]

Good evening everyone, I have a problem that perhaps someone has seen before and can help.

I am using the one wire library found in this forum and it works great. I am using a PIC18F8722 at 10MHz. If I use the fuse H4 to give it 40MHz the one wire routines fail.

Anyone had this happen before?

Thanks in advance,

Steven
_________________
"I am always doing that which I can not do, in order that I may learn how to do it."
- Pablo Picasso

[PCM programmer]

Post a link to the 1-wire driver that you're using.

[Douglas Kennedy]

One wire has very specific timing too fast or too slow and there will be issues. Most of this is often resolved by the use of CCS delay statements that are automatically adjusted for a change in the oscillator frequency. Now changing to H4 is not enough. The frequency in the #use delay must also be set to 40mhz. The delay is based on #use delay and not on the FUSE settings.

[smanzer]

Thank you for the replies everyone. I tinkered with the #delay and found no change - it works with 10MHz and fails at 40MHz.

I put some debug code in and found the problem was the ow_read_bit() function. Turns out the timing in this function would not work at the higher clock rate.

I searched this forum and found that user Swys had different timing than the original code I used. I modified to match Swys and bing it works!

Here is the corrected function:

[dynamitron]

A few days ago I had this problem and did not find a solution.
At the end I stayed frustrated at 10 MHz.
Now I will try your modified code.