Consider a USB to i2c adapter.  i2c modules of all types abound.
I could loan you my adapter that I bought from
                      http://www.i2cchip.com/    ($70)
They also have chips and modules ranging from $4 up.

Gus


> On Dec 26, 2009, at 10:25 AM, PICdude wrote:
>
> Hi all,
>
> I have been meaning to learn USB and to create a PC-based test
> interface with it, so that I can use a PC to simulate various
> sensors/triggers/signals to test products, and in same cases be able
> to measure the product responses and determine if they're correct,
> etc.  But time is difficult to come by lately, and I'm now looking for
> something off-the-shelf.
>
> I would need the following I/O...
> - At least 5 digital outputs (to simulate switching to ground, sending
> 5V and 12V power to the product under test, etc)
> - 2 analog voltage outputs (8-bit is fine).  I can use a couple D2A's
> for this, assuming I have a couple SPI/I2C outputs, or 16 extra
> digital outputs
> - 2 variable resistance outputs (I can use digital pots again,
> assuming I have enough digital outputs or 2 I2C/SPI outputs)
> - 4 digital inputs to test outputs from the products.
> - At least 36 (44 would be nice) extra inputs, which I'll use later
> with phototransitors to "read" some 7-segment displays, and have the
> PC interpret the results on the products.
> - 2 analog inputs.
>
> On the PC side I'd like it to have a direct USB connection to the PC
> (no serial-to-USB interface).   I'll need to write code so that the
> operator will select the product model/configuration, and it will
> setup the correct signals, tell the operator what the display should
> show, and they can click "pass" or "fail" to move to the next test
> step, so I need some type of scripting language on the PC side.
>
> Anyone doing anything similar?  Any commercial products do this
> already, at a non arm-and-leg price?  A generic I/O board with enough
> analog and digital I/O's would be nice, but I would need the PC-side
> scripting language to send/read the signals.
>
> Cheers,
> -Neil.
>
>
>
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