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I need to measure voltage between 0-10 volts using my Arduino Due. I have an ADS7805p chip, which I believe will work, but am not sure how to wire it on my breadboard. I'm used to just using the chip on the arduino, but that only goes 0-5 volts and I can't loose the resolution by converting. Can someone, please, point me to or instruct me on how to wire something like this to my arduino?

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Why not just halve the voltage? – Ignacio Vazquez-Abrams Sep 1 '14 at 4:06
    
When you say "using the chip on the arduino", I guess you mean "directly using the analog inputs of arduino", is that correct? – jfpoilpret Sep 1 '14 at 5:18
    
The important question here is: do you absolutely need 16 bits resolution (as offered by ADS7805 ADC) or can you deal with just 10 bits, or even 12 (as supported by Arduino DUE)? – jfpoilpret Sep 1 '14 at 5:20
    
If 10 or 12 bits resolution is OK, then @Ignacio suggestion is probably the best way to follow. – jfpoilpret Sep 1 '14 at 5:22
    
I do need 16 bit resolution. – 65ponyboy Sep 3 '14 at 2:09

2 Answers 2

up vote 1 down vote

The ADS7805 is old but still a pretty good ADC. I could imagine that you just have a few lying around that you want to use. I would simply wire it to two parallel in / serial out chips like the 74HC589 or CD4021 as used in this example:
http://www.arduino.cc/en/Tutorial/ShiftIn

Start the conversion as described in Duncan C's answer and then simply clock in all 16 bits. I think you could then probably get away with 4 or 5 control lines.

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Thanks for pointing to that Tutorial. Very helpful. – 65ponyboy Sep 3 '14 at 2:12
up vote 0 down vote

If you really need 16 bits of resolution then you could use that chip, but it's going to be a lot of work. Also beware that according to Mouser's website, it is not recommended for new applications. It sounds like it's being phased out/replaced.

Take a look at the data sheet linked from Mouser's website: ADS7805p datasheet

It has 16 bits of parallel data output, plus what sounds like 2 control lines, CS and R/(not)C (Don't know how to make the proper symbol.)

It sounds like you pull CS and R/C low to trigger a conversion, then wait for not busy to go low, switch R/C to high, then read the 16 bits of data.

To use this chip you're going to need 18 or 19 pins from your Arduino. You might want to consider a chip with a serial interface instead.

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I saw that bit about not being recommended for new applications. I'm looking around now to see if I can find a 0-10v one now. Thanks for the thought. – 65ponyboy Sep 3 '14 at 2:15
    
The due has plenty of pins, but they are 3.3v and the ADC uses 5v logic. – Chris Stratton Sep 3 '14 at 15:27

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