CCS C Software and Maintenance Offers
FAQFAQ   FAQForum Help   FAQOfficial CCS Support   SearchSearch  RegisterRegister 

ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

CCS does not monitor this forum on a regular basis.

Please do not post bug reports on this forum. Send them to support@ccsinfo.com

Measure video level with AD

 
Post new topic   Reply to topic    CCS Forum Index -> General CCS C Discussion
View previous topic :: View next topic  
Author Message
Andrew Wilson Jones
Guest







Measure video level with AD
PostPosted: Sat Jul 19, 2003 12:46 am     Reply with quote

Is the AD on any of the PIC fast enough to measure the voltage of a video wave form. On a PAL system If I count the sync pulses to get the required line then have a delay to get to a point on the line can I then use the AD to measure the voultage at that point. IE if I wanted to measure the Green bar of a coulour bar display. Each line on a PAL system is 64us long - front porch, back porch, colour burst etc leaves about 52us of signal / 7 colour = 7.5us over which the green is present. If not is ther any other way I could measure its level.

Thank Andy
___________________________
This message was ported from CCS's old forum
Original Post ID: 144516172
John Taylor
Guest







Re: Measure video level with AD
PostPosted: Sat Jul 19, 2003 1:07 pm     Reply with quote

This is simply a sample and hold problem. In the PIC A/D you charge a S/H cap in the PIC via a MUX from which the conversion is then done on. As long as the signal is present long enough to charge the S/H cap and you don't expect to do another conversion quickly there isn't a problem. What it really comes down to is the impedance between your signal and that cap, such that it has time to charge to the same value as your signal. A way to ensure this is to buffer the signal with an amplifier to present a low impedance to the A/D or to do an external S/H to eliminate the timing. The only real constraint is to not need to do conversions faster than the SAR clock allows.
___________________________
This message was ported from CCS's old forum
Original Post ID: 144516181
Display posts from previous:   
Post new topic   Reply to topic    CCS Forum Index -> General CCS C Discussion All times are GMT - 6 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group