How can I omit pullup resister.

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1

Hi, forks!
I got BBB and start enjoying.

I wonder How to work pullup pinmode at input in software.
http://beagleboard.org/Support/BoneScript/pinMode/

I want to pull up P8_31(GIPO_10) as Input 、but it effect noting.
1.b.pinMode(“P8_31”, b.INPUT_PULLUP);
2.b.pinMode(“P8_31”, b.INPUT, 7, ‘pullup’);
Both are in same result and P8_31 never pulluped.

Of course when I connected a 10Kohm resister between P8_31 and VDD3V3 , It pulluped and work fine.
I want to omit this resister.

Many chips (PIC & AVR & etc…) has software pullup mode and no need to connect extra resister. But In BBB It doesn’t work?? Always need extra resister?

My BBB’s info:
Your board is connected!

BeagleBone Black rev 00A6 S/N 4613BBBK1318 running BoneScript 0.2.2 at 192.168.7.2

I want some help, Please.

Thanks.

P.S.
I know in BBB it is limited 4mA or 6mA for GPIO current.
My question is total current limitation in BBB. Is there any limitation for total current?

2

Check the datasheet. The pull up may or may not be small enough depending on what it has to pull up. The current is the max the pin can do. In other words, that is who large the pull up actually is. Turning on all the weak pullups isn’t going to strain the total current of the power supply which is the real limiting factor. And there aren’t that many pullups you can turn on any way as most of the signals are used for other things on the board…

Gerald