0 Voltage = 1 Volt ??

Amaral

Trying out something at a Demo Board (RevG)
I noted that my pin 1 is giving 1 volt when set to 0 output (outa[1]~), and that wouldn't bother me for logic, but for turning an bi-color led on pins 0 and 1 it doesn't work (not enough voltage difference)

has anyone experienced the same ? is this mine ship with a problem or a series ?

Thanks in advance

Amaral.

MagIO2

Are you sure that you set the pin to output using DIRA?

Amaral

yeap ! right on the beginning.

Amaral

ErNa

did you measure with a scope? could it be, there is a pulse train? what happens if you load the output with a pot from lets say 10k to100 ohm, does the voltage change? And always remember: there is no such thing as ground ;-)

Ariba

Is this 1V with the LED connected and P0 on high level?
If so, have you a series resistor between P0 or P1 and the LED?

If the Pin has 1V without any connection, then something is wrong with the chip.

Andy

MagIO2

1V is definitely not the LOW-level an output should show. Did you try the same using another set of pins? This would show you if something with the PCB is wrong or the wiring? (Soldering bridge or shortcut). Or if you destroyed the pins in a previous project. (setting to output while the pin is already driven by an external device).

Amaral

Ariba wrote: »

Is this 1V with the LED connected and P0 on high level?
If so, have you a series resistor between P0 or P1 and the LED?

If the Pin has 1V without any connection, then something is wrong with the chip.

Andy

it has a 620 ohm resistor in series with the led.

P0 --- 620R --- LED ---P1.


and the pin output HIGH when I command it, There is NOTHING connected to it for testing, just the probe of the multimeter on pin 1 and the other probe in gnd. kind of flawless connection.

I don't have a scope here, I might try it on the weekend. (I'm at work that is the purpose of the demo board for me)

Is it possible to HALF destroy a pin on a previous project ? I don't think so, but is never late to learn new things !

No progress here still.

Thanks .. I'll keep looking for it and post latter.

Amaral

Toby Seckshund

You say that the resistor and LED are connected across P0 and P1, rather than either P0 OR P1 to ground. The voltage from a Pin which is high would be around 3 - 3.3 Volts, the voltage drop across a LED would be about 2 Volts (dependant on which colour it is).

Could the remaining 1 Volt be the 3 Volts minus the 2 Volts ?

Amaral

Forget about the LED , that was used just to detect the problem.

Just connecting a multimeter between P1 and Ground, set it High (dira[1]~~ and outa[1]~~) will gives me 3.3V ,now setting it output low (dira[1]~~ and outa[1]~) gives me about 1 volt on the pin 1.

I know it sound very very odd, but that is what I'm reading ! can't explain either, during the weekend I check with a bunch of other equip. (osciloscope, another voltmeter) and see what happens.

Thanks for the interest and help.

Amaral

localroger

Try one of the other open pins. If the other pins behave normally, and there is no other code running but dira[pin]~~ outa[pin]~~ then it probably means the pulldown transistor for P1 has been damaged within the Propeller chip itself.

Amaral

you are probably right localroger because no other pin behaves in the same manner.