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Delay between set_adc_channel ( 0 ); and read_adc()

 
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noyz



Joined: 31 Jan 2009
Posts: 59

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Delay between set_adc_channel ( 0 ); and read_adc()
PostPosted: Tue Jun 21, 2011 2:06 am     Reply with quote
What is the minimum delay between
Code:
set_adc_channel(0)

and
Code:
read_adc()

How is this delay calculated?

I have some app with 18f2550 and 18f8527.
I do believe it is a clock dependent.
For example : 8527 - clock 32Mhz - i have delay 400us .. if i put less than this value, the value is not entirely read,

I use this adc for touch screen and below 400us it doesn't get the right pixel pressed, when put 400 .. the right pixel is then selected/pressed.

Today i tried a simulation in Proteus with 2550 @48mhz, and delay_us 40 and at messages log in Isis i got adc time too small.
temtronic



Joined: 01 Jul 2010
Posts: 9163
Location: Greensville,Ontario

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PostPosted: Tue Jun 21, 2011 6:45 am     Reply with quote
Short answer is 400us in your program....


Long answer is to read the ADC section in the datasheet for the PIC you're using. Evrerything you need to know is clearly spelled out for you including various timings relative to which adc clock you choose.

Your query doesn't have enough info for anyone to properly answer.
However you've setup the adc , it needs 400us...not the fastest it can be though.
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