USB in python
Lie Ryan
lie.1296 at gmail.com
Tue Jan 27 05:31:25 EST 2009
On Mon, 26 Jan 2009 11:08:48 -0600, Unknown wrote:
> On 2009-01-26, Lie Ryan <lie.1296 at gmail.com> wrote:
>
>> How about (a crazy idea) using the audio jack out? (DISCLAIMER: Little
>> Hardware Experience). High pitched sound (or anything in sound-ology
>> that means high voltage) means the device is on and low pitched sound
>> off.
>
> 1) Pitch has nothing to do with voltage. A high-pitch sound
> and a low pitch sound can have the exact same voltage.
>
> 2) The OP's device requires quite a bit of power. There is
> almost no power available from the line-out jack, and the voltage is
> limited to about 1V. If his sound card has a power-amp (none do
> these days), he might be able to get a usable amount of power.
>
>> The device will need an additional transistor to separate low voltage
>> from the high voltage.
>
> He'll need more than a transistor. He needs a power supply, some sort
> of rectifier/detector, and a comparitor. It would be more interesting to
> use notch filters to detect different frequencies so that you could have
> multiple output "bits".
>From the little I know on electronics, a simple, single transistor would
(almost) immediately switch from on-to-off-to-on depending on the voltage
of the control pin (I think it was the middle pin). I was suggesting this
simplistic hack because as far as I comprehend the OP's need, he only
need on-off switch instead of a complex multiple output bits.
>> I don't know how much power can be pulled from jack out,
>
> Almost none, and what's there is very low voltage.
That's why the power is taken from USB port.
>> but for a home brewn device it is still feasible to draw power from USB
>> and signal from jack out.
>
> It would probably be easier to buy a USB-parallel port chip. Then he's
> got power from the USB bus and something like 14 parallel I/O pins he
> can control. Alternatively A USB-serial chip will provide 2 outputs and
> 4 inputs.
The idea was made on the basis that a USB microcontroller is not used.
Getting power from USB should be much easier than getting data while the
jack out can provide simple on-off signal.
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