AU335 GPIO Output/Logic Levels

I have an AU335 that I'm planning on activating by a 5 volt motion sensor.  I have the 5 volt motion sensor activating a relay, which is working fine as a dry contact switch for the GPIO input on the AU335.

I'm currently using a 16 port SainSmart Relay Module.

In addition to playing the corresponding output audio file, I also want to light up a nice bright 12 volt LED.  I have the GPIO 0-3 set as inputs, and 4-7 set as outputs.  The presentation I have setup in BrightsignAuthor:Connected has the entry/exit commands set for each audio file to turn the GPIO port on/off when the sound begins and ends.

It's close to working, but it seems that the GPIO output of the AU335 is not dropped down to zero volts, rather "off" = ~38.2mV on the multimeter.  When the sound file plays, the "on" is = 3.3 volts as I expected.   The issue is that the SainSmart relay board is considering that 38.2 mV to be a voltage, and activating the relay.  Do I need to add in a pulldown resistor to get that "off" value to zero or is there some other way to set "off" to be truly off?  If so, help on calculating the right resistor values would be appreciated.  Thanks...

1 comment

Please sign in to leave a comment.