Piggybacking ADCs

Well, this has been a waste of time...

Not to mention the spam and crap all over this site... this is a disgusting example of a discussion system.

Strange, I didn't see your post of Dec 3rd, perhaps others didn't either. As you know usenet is not a privately-run network, and it is therefore vulnerable to misuse. But despite this, many of us still prefer it to various privately-operated discussion systems. Thankfully it's not usually as bad as it has gotten to be lately.

WRT your question, asking about the rate of return to +5 after release of a pulldown switch, we have to ask, how much capacitance is on that shared line? How slow is the risetime you observe, and does this match your high-Z oscilloscope-probe observations?

When your question is full of vague descriptions like:"My problem at the moment, if I connect the pin directly to the second micro, is that when buttons are pressed, the value is correct while the button is held but when released the voltage takes time to return to 5v, during which time the first micro reads different values, resulting in wrong outputs...," no one is going to bother trying to answer because we can only guess what you're working with. The fact that you describe what is possibly the ADC input of a micro as a "pin" and the voltage takes "time" to do this or that is a "disgusting example" of attempting to ask a question...

--- If this is what you're doing, then switch bounce is going to eat you alive: (View in Courier)

Vcc>----------+ |R1 [10K] µC1 | +-----+ +----+----|ADCIN| | | +-----+ [R2] | ___ | | µC2 +--O O--+ | +-----+ | S1 | +----|ADCIN| | [R3] +-----+ | ___ | +--O O--+ | S2 | | [R4] | ___ | +--O O--+ . S3 . . [Rn] . ___ . GND---+--O O--+ Sn

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--- I doubt whether that's the problem, but if it is it's easily remedied like this:

Vcc>----------+----------+ |R1 | [10K] | | | µC1 +----+----|+\\ +-----+ | | | >--+--|ADCIN| [R2] | +-|-/U1A| +-----+ ___ | | | LM358| +--O O--+ | +-------+ | | | | [R2] | µC2 | ___ | +----|+\\ +-----+ +--O O--+ | >--+--|ADCIN| | | +-|-/U2B| +-----+ | [R2] | | | | ___ | +--|----+ +--O O--+ | . . | . [Rn] | . ___ . | +--O O--+ | | | GND---+------------------+

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--- Maybe...

How are you starting your A to D conversion and how are you determinin whether a button is pressed or not.

I don't mean _which_ button was pressed, that's easy enough, but how are you determining whether _any_ button has been pressed? Perhaps a change in the ADC input voltage from the rest state?

-- JF

It isn't a 'site', it is 'Usenet' that you are accessing through 'Google Groups' piss poor HTML portal to Usenet.

Ironically, most of 'the spam and crap' you are complaing about is posted by 'Google Groups' users, like yourself.