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Re: proper feeding of UART.

 From: Lee Adamson <>
>Ok, I'm thinking about switching my power supply to a couple of 4 volt Wheat
>open-faced wet-cells (for 8v total) and have some questions to ask before
>frying my hardware.
>
>I believe the rs232 spec says that a zero is -12 to -3 volts, nothing is -3 to
>+3 volts, and one is +3 to +12 volts, right?
>
>So, afaik, the only thing that I'm using +12 and -12 from the ISA bus is for
>the serial UARTs.  Will they get mad an maybe even die if I replace the +12
>with +8 from the batteries, and replace -12 with -7 via an op-amp wired as a
>charge-pump thingie?  This would fall within the rs232 limits...

If you really need +/- 12V for uarts (there are some uart's that are
designed to take 5V in, and have internal chargepumps), and it's just
for uart's, then you might look into just getting some micro charge
pumps from maxim.  They're great for samples (read: free!)

see http://www.maxim-ic.com/

   - Kevin

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