Comparator Help reqd

[G8RPI]

Hi,
The 16F630 divides down the Vdd for it's reference and the usable input range is about 0.3 to 3.5V with a 5V Vdd. the resoultion is about 0.15V (Vdd/32).
Depending on your application, it may be worth considering the 16F676 with it's 10 bit ADC. The ADC allows you more freedom to add filtering etc in software.

Robert G8RPI.

[Squibcakes]

Hi Rob,

At this stage, I'm just learing the basics (with a 16F628A), so I'm not ready to decide on a chip for that reason. (But thanks for the info)

I have been able to get the comparator working using an external Vref by resistive divider network, and it works quite well. This I am ok with. (thanks to mister_e's simple code example).

However, no luck when trying to use the internal voltage reference.
I think this is my problem...

The datasheet is not very clear when setting the VCON VR<3:0>: bits.

For example, the datasheet states that the voltage reference specs should be
3.0V < VDD < 5.5V

But by following the formula for configuring the voltage reference I get values between:
0 to 3.13V for VRR=1 and
1.25 to 3.59V for VRR=0,
assuming VDD=5V.

Also, on another matter, if we want to output the internal Vref to RA2, (to monitor this voltage), should we set TRISA.2 to an output pin?

Any Ideas?

[Squibcakes]

Ok,

I have searched this forum and found a good link to Melanie's Comparator Tutorial. Fantastic, even for a dummy like me.

http://list.picbasic.com/forum/messa...tml?1020960642

Hope this helps anyone else out there.

J

[Melanie]

Goodness... I didn't think that old thread was still in existance - let alone folks reading it!