[TI-H] Re: Calc Port Voltage
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[TI-H] Re: Calc Port Voltage
Shyam,
Those step-up and step-down circuits look like exactly what I
was imagining...now we are faced with a problem. Those were designed
for an SPI interface which is a three wire serial bus. Basically input
line is separate from output. On the calc we only have two wire. One
is undoubtedly the Clock line while the other must be used from input
and output. So we need to have circuitry to step-up the voltage from
the IC and step-down from the calc...all on the same line. Before doing
anything however I think it would be a good idea to try using the 3.3V
for the IC and see if the calc can recognize 3.3V as a "1". I believe
it should. This will require connecting the IC directly to the calc.
Also use a 2K-Pullup to 5V on that line. I do not believe this will
hurt the IC as they usually have protection Diodes internally on each
pin. Try this and see if it works. Remember to use the pull-up to 5V
as it will more than likely be necessary. Let us know the results.
Regards,
Cullen Logan
-----Original Message-----
From: ti-hardware-bounce@lists.ticalc.org
[mailto:ti-hardware-bounce@lists.ticalc.org] On Behalf Of Shyam
Dwaraknath
Sent: Sunday, August 18, 2002 2:39 PM
To: ti-hardware@lists.ticalc.org
Subject: [TI-H] Re: Calc Port Voltage
Here are the circuits. I just took them from another site cause I was
spending most of my time designing the circuits for the Xe1202. Step
<http://instruct1.cit.cornell.edu/courses/ee476/FinalProjects/s2000/pete
rdan/stepup.jpg> Up Step
<http://instruct1.cit.cornell.edu/courses/ee476/FinalProjects/s2000/pete
rdan/stepdown.jpg> Down
References: