I'm having a small problem with some of the voltge reference settings.
The last two bits in the FVRCON register should set this voltage.
11 gives 4.096V which works
10 gives 2.048V wich also works
01 should give 1.024 V but the ADC reading comes out at 60144 which translating from two's compliment format gives -4096 for all voltage values on the ADC pin (I have Vref negative set to Vss).
So any ideas why the 1.024 V does not work as expected.
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Thanks for the feedback.
I expect you have saved many people a lot of time there, forewarned is
forearmed especially with all the new Analogue Peripherals that Microchip
are starting to add.
I've been merrily skating along with 2.048V FVR as Vref. Now I know there is trouble if I ever wanted to drop it down a notch. Thanks for the heads up.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
I'm having a small problem with some of the voltge reference settings.
The last two bits in the FVRCON register should set this voltage.
11 gives 4.096V which works
10 gives 2.048V wich also works
01 should give 1.024 V but the ADC reading comes out at 60144 which translating from two's compliment format gives -4096 for all voltage values on the ADC pin (I have Vref negative set to Vss).
So any ideas why the 1.024 V does not work as expected.
Found the problem. It is well hiden in the datasheet that the minimum ADC ref voltage is 1.8.
Thanks for the feedback.
I expect you have saved many people a lot of time there, forewarned is
forearmed especially with all the new Analogue Peripherals that Microchip
are starting to add.
Cheers
Chris
On Fri, Oct 23, 2015 at 8:34 PM, David Stephenson uwidavid@users.sf.net
wrote:
I've been merrily skating along with 2.048V FVR as Vref. Now I know there is trouble if I ever wanted to drop it down a notch. Thanks for the heads up.