Maybe a bug

[gkalog]

Hello ehayon

I got the following situation ,,,

I have to change a pin on my BeagleBone (INPUT or OUTPUT) many times in my c program.
At boot the pin is input. and has high impedance.
During my program I change the pin as output ( pinMode(P8_44,OUTPUT,7,PULLUP) ; ) and I write to it HIGH or LOW ( digitalWrite(P8_44,HIGH) ; or digitalWrite(P8_44,LOW) ; ) .
When I make again the pin input ( pinMode(P8_44,INPUT,7,PULLUP) ; ), the pin does not have high impedance.

Looking at the sysfs I got that the pin is INPUT.

thank you in advanced for your help

[ehayon]

Hi,

At what rate are you switching the pin from INPUT to OUTPUT? (What's the delay between switching, in milliseconds or nanoseconds)

Just so I can get a better understanding of the problem and test it out myself. Do you have a code snippet I can test to replicate the problem?

Thanks,
Ethan

[gkalog]

Hi Ethan

Thank you for your immediate reply

i run the following simple program

main()
{ pinMode(P8_44,Input,7,PULLUP); sleep(1);
pinMode(P8_44,OUTPUT,7,PULLUP); sleep(1);
digitalWrite(P8_44,LOW); sleep(1);
pinMode(P8_44,Input,7,PULLUP); sleep(1);

while(1){}
}

before I run the programm I connect to the beaglebone pin P8_44 a square
wave signal (peak to peak 3,2V)
with an oscilloscope I can see the 3,2V signal.

after I run the program I have a high input load and on the oscilloscope
the signal is 2V peak to peak.

If I change in my program the order digitalWrite(P8_44,LOW); to
digitalWrite(P8_44,HIGH); then I have also a high load and no signal at the
oscilloscope (only 3,3V).

If I do not include the order digitalWrite everything is OK.

Thanks
Georgios

2012/11/10 Ethan Hayon notifications@github.com

Hi,

At what rate are you switching the pin from INPUT to OUTPUT? (What's the
delay between switching, in milliseconds or nanoseconds)

Just so I can get a better understanding of the problem and test it out
myself. Do you have a code snippet I can test to replicate the problem?

Thanks,
Ethan

Reply to this email directly or view it on GitHubhttps://github.com//issues/2#issuecomment-10259625.

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[ehayon]

Hmm, now that I think about it, is it even possible to enable pull-up/down resistors for an output?

Let me look into this and I will get back to you.

Thanks,
Ethan

[gkalog]

2012/11/10 Ethan Hayon notifications@github.com

Hmm, now that I think about it, is it even possible to enable pull-up/down
resistors for an output?

Let me look into this and I will get back to you.

Thanks,
Ethan

—
Reply to this email directly or view it on GitHhttps://github.com//issues/2#issuecomment-10260347

In parallel I will try the code with out PULLUP.
Also what is the value of that internal resistors ? maybe I have to search
at the manual

Georgios