What's wrong in simply adding a
'v'
command to your
{'o', 'f'}
command set just to get the voltage from the arduino?
[update]
Something like
if (data=='o')
{
digitalWrite(LED,HIGH);
}
else if (data=='f')
{
digitalWrite(LED,LOW);
}
else if ( data=='v')
{
}
else
{ }
Of course you have also to adapt properly the
C#
side.
[/update]