Gpio problem Rpi

What power supply are you using and what current output does it have?

With no power attached and your multimeter set to ohms what is the resistance across the fuse?

If you measure the resistance (with no power) between V+ and ground, do you get a low reading as in less than 100 ohms or much greater?

If you measure your voltage with nothing attached to the GPIO pins do the voltages become correct?

What do you have attached to the GPIOs at the moment and have you checked that for a short?

Are the chips on the Pi (or anywhere for that matter) getting hotter than allowing you to either hold your finger on them, or hold and then remove?

Colin

5v 1.3A  micro usb  power supply

"If you measure your voltage with nothing attached to the GPIO pins do the

voltages become correct?"

Yes that time am getting 3.2v

There is no short circuit am just checked using LED

The circuit is not too hot i can hold the fingure on chips

Every thing else is proper, I can able to see the desktop also

Thanks & Regards

SREEJITH MURALI

sreejith m wrote:

 

5v 1.3A  micro usb  power supply

 

"If you measure your voltage with nothing attached to the GPIO pins do the

voltages become correct?"

 

Yes that time am getting 3.2v

 

There is no short circuit am just checked using LED

 

The circuit is not too hot i can hold the finger on chips

If I understand you correctly, you're saying that if nothing is connected to the GPIO then your RasPi works fine with +3V3 reading 3.2V.  Then when you attach an LED to a GPIO, +3V3 drops to 1V.

If this is the case, it sounds like you may have burned out your LED and converted it into a short circuit.  An LED must have a current-limiting resistor (1K is a good starting value) in series.  Otherwise if you hook it up to +3.3V or more it will give off a very bright light once and then turn into an open circuit or short circuit.  Does your LED still work connecting it between +3.3V and ground, with a 1K current-limiting resistor?

JMO/YMMV

Sounds to me that using your led to check the 3v3 (without a resistor) has caused the polyfuse to operate.

These often need 1 or 2 hours to reset themselves as they are thermal devices.

Often leaving the Pi un-powered overnight fixes it.

Mark

Am using resistor of 270ohms,and it happens 1day back

According to me that is approx 6mA, and should have no effect.

A mystery then, since you appear to have you 3v3 back.

Mark

On AVR processors, if you configure a pin as "input", setting the "output" bit will enable a "weak pullup". This is normally so weak that you wouldn't see a led light up. (it can be seen when you try and with an efficient led, but it's much weaker than you'd expect from a led).

It works a bit differently on the BCM2835, but still it sounds as if you're just playing with the "weak pullup" instead of the output bit.

Do you have a multimeter? Put a 220 ohm resistor (*) in series with your multimeter in "current" mode. Measure the current out of the GPIO pin. about 15mA is what we expect, 12-18 would be "expected". If you get say 60 micro A, that would be a "weak pullup" in action....

The raspberry pi GPIO pins are 3.3V, so lighting a 3.6V white led is not going to work. What color led do you have and what does your supplier claim as the forward voltage?

(*) I see you have a  270 ohm resistor. That'd be fine too.

Pls understand that am telling about 3.3v Power pin am not getting power to that pin after a boot up but am getting 3.3v when didn't inserting memory card

So 270 ohms is not enough? what should i do now i have tried after 24 hrs now.

Who told you 270 ohms is not enough?