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with ice cream
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RPI2 and GPIO issues [solved/explained]

Tue Mar 03, 2015 12:46 pm

I encounter strange GPIO behavior on my RPI2. I use a PIR module and activity is detected when there isn't actually any (quite annoying for a motion controlled light source). An LED flickers when a IR emitter (connected to a different pin, of course) sends out pulses. I already switched the LED pins without improvement.

What can I do to get to the core of the problem?
Last edited by with ice cream on Wed Mar 04, 2015 7:32 pm, edited 1 time in total.

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joan
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Re: RPI2 and GPIO issues

Tue Mar 03, 2015 12:55 pm

Posting a photo of the connections you have made may be useful.

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with ice cream
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Re: RPI2 and GPIO issues

Tue Mar 03, 2015 1:56 pm

Thank you joan for the suggestion. Since the same setup didn't show this behavior when it was connected to a B+ I am not sure if a picture would help. When I ran into issues related to IR emitters it required a bug fix and now I am wondering if I am in a similar situation.

I will try your piscope to verify my observations.

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with ice cream
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Re: RPI2 and GPIO issues

Tue Mar 03, 2015 9:35 pm

I checked all connections, everything is as it should be. I checked with piscope what happenes when I send an IR sequence (through BCM pin 24). As is to be expected the same sequence appears on the pin where the IR receiver is connected (pin 18). The pin (13) where the flickering LED is connected doesn't show any activity. But the scope also shows no change when I set the LED's pin to on via the command line with GPIO write.

I am at a loss.

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with ice cream
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Re: RPI2 and GPIO issues

Wed Mar 04, 2015 7:32 pm

I found the reason for the issue what I am observing.

In my setup an LED flashes once when an IR sequence is received. Now when I send a sequence it gets at the same time picked up by the receiver and the LED starts flashing. It seems the sent sequence repeats several times which leads to multiple flashes.

Should LIRC really receive and send simultaneously, has it always been like that, is there a way to deactivate it?
If it cannot be solved within LIRC, can I disable one pin while another is active?

I'll close this thread and open a new one.

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