Check if ADC is giving real values or floating values

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1

hey guys,

I’m pretty new to this BBB. I’m trying to read values from ADC pins. It works as expected when I have connected ADC pins to power.
But when pins are disconnected from power, it still gives values. Sometimes these values are pretty close to real values.

How can I filter them out??

Thanks

2

Some pins have pullups on them in touchscreen mode. I can’t tell you how to do it, but you need to turn those pullups off.

Gerald

3

hey Gerald,

you are helpful as always. can u please give me few hints about pullups? i tried googling, but couldn’t understand much.

thnx

4

You need to look in the TRM for the processor.

http://www.ti.com/product/am3359

Gerald

5

hey Gerald,

you are helpful as always. can u please give me few hints about pullups? i tried googling, but couldn’t understand much.

thnx

Some pins have pullups on them in touchscreen mode. I can’t tell you how to do it, but you need to turn those pullups off.

You probably need to read up on the DeviceTree and setting the mode for each pin. Best place to read about device tree is here:

https://github.com/jadonk/validation-scripts/tree/master/test-capemgr

Regards,
John

6

thnx john, will check it out