Q: I would like to wire a stereo headphone socket for the Bitsy audio channels. What do I need to do?
3.5mm audio jacks for headphones are normally wired as shown in the following diagram:
The easiest way is to drive both channels of the headphone with the same signal (mono mode). For this case, simply connect the (+) audio output line to tip and center bands of the jack, and the (-) to the shell. Note that if you're using the UCB1200 output, impedance of each headphone speaker can't be less than 16 ohms.
If you need stereo mode, the connection is a little more complicated. Each of the stereo output driver pairs is bridge tied. That means that each of the four lines (+/-, R/L) is active. To connect stereo headphones, which use a common ground, you'll have to use the take one output from each channel, run it through a capacitor and then out to the jack. Connect Bitsy ground to the shell of the jack. Select your blocking capacitor size based on the lowest frequency you want to be able to play out (fo=1/(2*pi*R*C). A 330uF cap into an 8 ohm speaker will give a low cutoff frequency of 60Hz. Use at least a 5V or 6.3V cap.
For further reading about Windows CE audio, please see the CE Audio topic index.
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Wiring a headphone socket for Bitsy
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Posted - 21 Feb 2002 : 13:41:15
