[Ovmsdev] 12V A/D conversion

Mark Webb-Johnson mark at webb-johnson.net
Mon Feb 25 00:40:59 HKT 2013


I've looked, but can't find the original reference code I used. But, it does seem similar to:


I think that is either my reference, or some variant of it.

Regards, Mark.

On 23 Feb, 2013, at 6:07 PM, Michael Balzer <dexter at expeedo.de> wrote:

> Mark,
> I got some 12V alerts during the last 3 days. Checking the 12V reading after the alerts showed normal level, so I'm trying to figure out if they were false alerts.
> Last alert was about 2 hours ago, alerting about 11.0 V -- my check only a few minutes later showed 12.1 V again...
> I've read into the PIC18 doc on the A/D conversion (chapter 19). AFAIS inputs_voltage() differs from the example in two ways:
> 1) the example does not turn off the converter after reading the result (but I understand the ADRES register should keep the result)
> 2) the example step 3 says "wait for acquisition time if required", it seems our function currently does not wait.
> "To determine acquisition time, see Section 19.1 “A/D
> Acquisition Requirements”. After this acquisition
> time has elapsed, the A/D conversion can be started."
> Section 19.1 contains an equation based on hardware parameters I don't know. Can you please have a look and tell if missing that wait time could lead to false measurements?
> Thanks!
> Michael
> -- 
> Michael Balzer * Paradestr. 8 * D-42107 Wuppertal
> Fon 0202 / 272 2201 * Handy 0176 / 206 989 26
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