Originally Posted by geekmaster
Oops.. this thread was about the touch, and I was addressing the touch, but my fingers were accustomed to typing K4 along with Touch (from all the debricking posts). But now that you opted to focus our discussion on the side-subject of "no sound on the K4", let's discuss just that for a moment:
The K4 needs a PWM driver to optically-couple audio out the power LEDs, and color-filtered photodiodes to feed stereo audio into an audio amplifer. And software, of course.
P.S. Don't ask me "when" -- that project is WAY down on my "To Do" list. You can probably PWM the accessory power port (square metal pads on the bottom) to drive a speaker directly (with a current-limit resistor), if mono sound is okay. The pad just below the USB port is GND, and the other pad is +4V when enabled.
Or you *could* go "old-school" and put it next to an AM radio and use controlled RFI to "transmit" audio to the radio.
And now that we know these things have external OTG USB ports, you can plug in a USB "sound card", but you may need to power it from the accessory port pads. Check this out for your K4 headphone jack: http://mightyohm.com/blog/2008/10/in...audio-adapter/
It looks small enough to fit INSIDE the K4, if you remove its plastic case and USB jack and solder it inside the K4. Perhaps the K4 has an unused "host-only" USB port for a future 3G modem?
We are usually limited only by our imagination.
Great ideas! We should go for a start-up with this sqeezing out some money from a hedgefond. At least as safe as throwing it to Greece.