I figure it's time to dust off my Due or RaspberryPi and try to make some use of them and an ideal project for me would be a TDR to measure cable lengths to detect breaks and I'm hoping someone can answer a few questions.
Glancing at the SAM datasheet I cannot see an analogue comparator and was wondering if I have overlooked this or if it truly does not have one.
I can also see no mention of the rise times on the digital I/O pins, just some info on XIN clock input. So wondered if anybody knows what the rise time is.
Final question for now is what is roughly the smallest duration the Due is capable of measuring.
It does seem that the SAM chip does not have a comparator peripheral - that's not to say you can't make one using two input pins and some software.
As for rise time - what sort of application is this where the rise time might be too slow? Get a fast oscilloscope out and have a measure, if you have access to one.
At about 1 foot per nanosecond, a 6-foot round trip would be 12 ns,
or about one clock cycle of the 84 mHz Duo. So, if you are just able
to count clock cycles, and have the return signal create an interrupt
(for fast response), your resolution might be as good as 6 feet, right?
garygid:
At about 1 foot per nanosecond, a 6-foot round trip would be 12 ns,
or about one clock cycle of the 84 mHz Duo. So, if you are just able
to count clock cycles, and have the return signal create an interrupt
(for fast response), your resolution might be as good as 6 feet, right?
I have moved on with this idea but will be using external components to measure the time instead.