Beginner in need of help !!

[Amoque]

Not sure how much help you need. I'm assuming you know input/ output, high/ low...

Google "Pull down switch" and see how the level goes from high to low when the button is pressed (there is a pull up as well); use standard input technique to read the level change when the switch is pressed. To control the LED output, I think an if/ then will work well:

If Button press = 0 and LED = off then [turn on LED]
If Button press = 0 and LED = on then [turn off LED]

You should also look at "debounce" as there is some issue to mechanical switches.

Also, without some programming to limit the speed, the switch will turn the LED on/ off very quickly. A pause will work (to give the user time to release the button) or, you can look for a "1" on the switch (released) before allowing another button press to register.

HTH,

[robbo78]

Okay I think I have made sense of this now - correct me if I'm wrong.

So if I wanted to set the comparator up with say an internal reference & output (cm<2:0> = 011), I would set the cmcon0 register as CMCON0 = %00000011 ?

Now to the VRR -

I think Im right in saying that the comparator uses the main VDD+ pin on the chip to compare the internal reference to? What I dont understand is this -

IF VRR=1 and VR3 ... VR0 = 1111 (15) with a VDD of 5V the Vref will be (15/24)*5 = 3,125V

^^ Where are they getting that 15 from? Also where do you get the 24 from?

IF VRR=0 and VR3 ... VR0 = 1111 (15) with a VDD of 5V the Vref will be 5/4+(15/32)*5 = 3,593V

^^ Also why has the 24 changed to a 32 just from vrr=1 changing to a 0?

One last question, Am I right in thinking that you have to use the CIN- pin on the chip to provide the voltage to check? Cant you use a comparator on any pin of the chip (apart from gp3, vdd & vss).

Thanks again,
Rob