SparkFun Forums

[sebmadgwick]

I have my XBee radio streaming its 6 analogue inputs and my PC displaying these values on a real-time graph. A potentiometer (between VDD and GND) on each channel gives the expected behaviour.

It would be useful to use the internal pull-ups for other types of sensors but it seems that the pull-ups are not compatible with the inputs in analogue mode. I left each analogue input floating and enabled/disabled pull-ups to find that the analogue values did not change from the floating behaviour.

Can anyone confirm if the internal pull-ups are compatible with the inputs in analogue mode?

[waltr]

I would say the internal pull-ups are for digital IO only.
This is the typical behavior for most processor IO pins that have analog features.

However, did you test the pull-ups on an analog input without an external device connected?
The pull-ups are rather weak (>100k Ohm) so it would not take much drive current to over ride the pull-ups.

[sebmadgwick]

I tested them while floating externally and they behaved as floating. I mainly use Microchip devices and was surprised when I found out that Arduino pull-ups apply to analogue, I wondered if XBee were the same... I guess not.