Subject:
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Re: Serial Communication with HP48 calculator
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Mon, 7 Sep 1998 14:43:30 GMT
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Original-From:
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Fred G. Martin <fredm@media.mit^NoMoreSpam^.edu>
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Viewed:
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3908 times
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> 1. Is there a version of the 9600 baud driver that supports input?
not that i am aware of. you could connect to the HB's phone jack as
long as you don't have to talk to interactive c and your calc at the
same time. see the FAQ serial answer.
>
> 2. Any suggestions that might help me use the serialio.c code and the
> SPI?
the SPI is for high speed SYNCHRONOUS comms (data and clock line).
RS232 is ASYNCHRONOUS (data only). SPI doesn't do RS-232.
> 3. What is the difference between the inverting and non inverting
> driver code?
the normal voltages of RS232 are -10v is logic 1, +10v is logic 0 (non
inverted, desktop levels). the MAX232 chip on the HB's serial
interface card converts these into +5v logic 1, 0v logic 0 "TTL or
microprocessor level" voltages (inverted).
your calc apparently talks at the inverting, TTL level voltages -- it
would need a ckt like that on the HB's serial interface to talk to a
desktop computer.
thus, you can wire direct from the HB's phone jacks to your calc using
the SW drivers presented in the FAQ.
>
> Thanks in advance!
>
> Fred Fotsch
>
>
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