Beginner in need of help !!

[richard]

the low range internal vref gives you 15 steps of 0.208 volt steps starting at 0v
the high range internal vref gives you 15 steps of 0.156 volt steps starting at 1.25v

if you don't need the cout as an actual physical output CM<2:0> = 110 is a better choice
and lets you chose pin 6 or 7 as your input (select with cmcon0.3 "CIS")
why waste pins on a 8 pin chip

0000=0
0001=1
0010=2
0011=3
...................etc etc
its called binary

[robbo78]

Edit: just re-read your post. I need to be able to read a pin & output on it at the same time (obviously with pauses, so do I need to use comparator with output?

Hi Richard, I just came back here from doing a bit of googleing. It took me about 2 mins to figure out that its just binary, maybe if I had paid more attention in Maths I would know this!

I now understand the voltage steps as well, everything is coming together now, its actually quite simple once understood.

I still need to know if you can use a comparator with internal reference on any pin or does it have to be the CIN- pin?

Cheers,
Rob

[richard]

if you don't need the cout as an actual physical output CM<2:0> = 110 is a better choice
and lets you chose pin 6 or 7 as your input (select with cmcon0.3 "CIS")

input to comparator is [ cin+ pin 7] or [cin- pin 6] with CM<2:0> = 110 its your choice

there are other modes but in all cases cin is only on pins 6,7

[richard]

if you need or can use the comparator output use CM<2:0> = 101
it still lets you chose pin 6 or 7 as your input (select with cmcon0.3 "CIS")

[robbo78]

Okay Richard thanks for your help.

So lets say I wanted an LED to be OFF if the voltage on cin+ is below 1.1v, & LED to be ON if the voltage is higher than 1.1v. Would I use this -

VR3 ... VR0 = 1000 (8) with a VDD of 3.3V the Vref will be (8/24) x 3.3 = 1.1V

I hope this is right lol

[richard]

there is not enough info to answer

what comparator mode ?
what cis setting
is vrr set
what cinv seting
how is led connected ?

[robbo78]

Richard, I'm specifically talking about just the VRR nothing else. I just want to know if I've got the workings out right. If you need the whole code to tell me if that part is right or not then I can do that no problem.

[richard]

that is correct it will set the reference to 1.1 for a vdd of 3.3v