Hello,
In the manual, it is written : "The GPIO outputs have 100Ω series resistors; the GPIO inputs have 1K pullup resistors to 3.3V; and the input threshold on the 541 chips is 2V high and .8V low. The high voltage is not problematic, but the low voltage can be if there are too many inputs connected to one output."
I would like to know what is exactly this "high voltage" ?
Thank you
Hi Maxime,
In case you were worried that high voltage was a voltage that is high enough to cause damage to the Brightsign. This is not what they are taking about. THe high voltage is any voltage over 2 volts, which is considered by an GPIO input pin to be over the threshold for setting the an input to ON in the brightsign.
From the documentation on GPIO:
A voltage on a GPIO pin of 2 volts or above is considered HIGH. A voltage of 0.8 volts or below is considered LOW. Anything in between is in the lap of the gods and may register as either HIGH or LOW. For that reason you want to make sure you have a clear voltage level or either, over 2 volts or below 0.8 volts to determine the correct state or your inputs and outputs.
Its not really a problem for inputs, but if you are driving multiple simultaneous outputs, its possible to lift the voltage floor above 0.8 volts. The example table at the bottom of the article is very helpful at explaining how multiple outputs can do that.
Ok, thank you for your answer.
I plan to use a sensor which has PNP output and higher supply voltage than 3.3V. So my question was rather which maximum voltage (5V, 9V, 12V ...?) can handle the GPIO inputs. I got this answer from Brightsign support :
Generally the player's GPIO lines can source or sink up to 3.3v at 24mA - anything more can blow the line