help with BASIC STAMP 2 sampling

dynamitekilla

Dear Reader,

·· I am trying to perform ADC with my BASIC stamp 2 but need to know the sampling frequency that the stamp reads in the data using the AD0831 chip. Please tell me if I am wrong with the following; using a basic stamp 2 module with a clock of 20MHz, the ADC needs about 8 clock cycles to convert the data and another 8 clock cycles are needed to transmit the data to the pc so this means 16 clock cycles in all. With a 20Mhz clock, 1 clock cycle = 0.05us so 16 clock cycles means 0.8us. Is the sampling frequency then 1/8 clock cycles = 250kHz ?


Alternatively, if I were to read the state change on a pin for a TTL input(0 and 5 only) then is the sampling frequency = 1 clock cycle =0.05us = 20Mhz ?

Thank you for taking the time to read my post. Have a pleasant day.

metron9

The ADC0831 uses a CLK pin so it dosen't matter what speed it is running at.


Attached file is from a google search of "AD0831"

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Think Inside the box first and if that doesn't work..
Re-arrange what's inside the box then...
Think outside the BOX!

sam_sam_sam

dynamitekilla

I can tell you that it reads very fast depending how long you rountine is and whether or not use any pauses in you routine if you are going to use a LCD
Display you do have to put little pause because they·are so fast that then LCD Display can not keep up I am just using pause 100 and that works great

It still is very fast· as fast as an volt meter is··When it is ·read voltage changes

I hope this helps


This is the link where I working on a project using the ADC 0831 Chip

http://forums.parallax.com/showthread.php?p=743395


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··Thanks for any··that you may have and all of your time finding them

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Sam

Post Edited (sam_sam_sam) : 8/17/2008 4:16:37 AM GMT

dynamitekilla

thank for the replies folks, but to produce accurate sampling I need to determine if I am fulfilling the Nyquist criterion or not to avoid aliasing and unwanted artifacts. I am sorry but I should have been more clearer. I am not using a display but rather I am saving the data to a file.

PJAllen

You're not reading PBASIC Help --

Quick Facts

Tracy Allen

The BASIC Stamp does not run anywhere near that fast. PBASIC is an interpreted language, which takes many many clock cycles at 20 mhz to read, decode and execute program tokens that are stored in a serial eeprom. Therefore the shortest time intervals for execution are on the order of 100 microseconds, and program times are measured in milliseconds, not microseconds. If you need sampling as fast as you say, you should consider the Propeller or the SX microcontroller instead of the Stamp. And that rapid of sampling will require machine language programming.

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Tracy Allen
www.emesystems.com

dynamitekilla

thank you PJ Allen for the timing diagram and Tracy Allen for the further clarification and confirmation. DO sincerely appreciate the help