On 16 August 2012 13:43, Wayne Merricks <[email protected]> wrote: > The manual for this card says "all I/O bits are set to a high impedance > input mode on power up and reset" and you should install pull up or pull > down resistors to get inputs to a known state. > > -- > Wayne Merricks > The Voice Asia
Note: I have some background in electrical engineering High impedance input pins mean that these pins have no (actually, a very small) current flowing in or out when you connect it to something. If you leave it floating, its behaviour is only defined by the electronic design. If you physically extend the pins using a cable, then this cable acts as an antenna. You must therefore use pull-up or pull-down resistors to force a known set. A pull-up resistor connects the input to a higher voltage (+5V, e.g.) while a pull-down resistor brings it to ground (0V). Your input will still be connected to the input pin. To find the resistor values, some maths are involved. You need to use a resistor high enough so that it will not disturb your signal source, but you need a value small enough so that it does not seem as if there was nothing connected at all. For switches and simple components, you may use a simple >1K, <1M resistor. -- Sébastien Leblanc _______________________________________________ Rivendell-dev mailing list [email protected] http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
