gpio voltages

[pfeerick]

Many compatible components exist that will work across a wide voltage ( which means they will work at 1v8, 3v3, and 5v ) but many more WILL NOT.  So , I don't get into the discussion of making exceptions ( if you're smart enough to figure it out, and if your components allow for it, great ! ).

Pity you didn't actually answer the question I asked That was the perfect time for you to link to a different sparkfun page :-P Since we all know that the VCC voltage doesn't always determine the comms/IO voltage. And that level shifters are good, but not always needed. The 'general discussion' is fine... but not when it doesn't actually answer the question.

So say I have a ADC0832, its a 5V piece, it has a Digital out at 5V, whats the best way to read the output?  Resistor in series?  How big?

What about the inputs to the ADC0832, they register voltages over 2 volts as a 1, can I hook the outputs to the ADC0832's inputs??
Thanks!

Unfortunately, TTL Output means that it it is a VCC level output drive, thus cannot be connected to the pine64 GPIOs directly, since you stated 5v. The Transistor-Transistor Logic (TTL) output essentially means the output voltage for a logic high will be anything from 2.7 to VCC (5v in this case), making it so that you cannot directly connect it to the pine64 (unless you intend to damage it!).

However, it is often used by Raspberry Pi people, and run at 3.3v, so if you have it, and the voltage you are measuring is between 0 and 3.3v, give it a try with a 3.3v VCC. Just be aware that since it has a ratiometric voltage reference, that the 'scale' will also be 0.0 to VCC If you want to learn a bit more about that part, see connection info, and some example code that you should be able to adapt for the pine64, have a look at Kolban's excellent free (or what you thing it's worth) Book on the Raspberry Pi, particularly the Analog to Digital conversion chapter. I would suggest though, that if you don't have a burning need for the ADC0832, 'upgrade' to the MCP3208, which has 12bit instead of 8bit resolution, and is also rated at 3.3v and 5v VCC by the manufacturer, meaning you're guaranteed it'll work