>
> Does anyone have any experience attaching an external A2D to the
> OOPic? I need some more resolution that the 10-bit on board A2D and
> would like to hookup a 12-bit to the OOPic. I just need a little
> direction to get started. If I can hook it to the I/O pins how does
> the OOPic interpret the digital information? Any help would be a
> appreciated, thanks.
>
You have 3 basic choices: I2C, SPI and parallel. I2C connects the chip
to the OOPic local bus (the one with the EEPROM) and since it is bit-
banged, transfers will be slow. Maxim MAX127 has an I2C interface
Maybe transfer speed and samples per second aren't important. If they
were, you wouldn't be using an OOPic.
SPI is a simple serial interface and quite common on A/D converters.
It is also bit-banged so, again, it won't be quick. I haven't examined
the datasheet in detail but the good news is that transfers are in
terms of 8 bit bytes which might be compatible with oSPI. Maxim
MAX1340 is one device.
Parallel devices such as the Analog Devices AD7891 need more than 16 IO
lines for the interface - 12 for data plus some for status/control.
The transfer will be very fast, as fast as the OOPic can read an
oDIOx. But there won't be very many pins left...
I think I would start at Analog Devices www.analog.com and do a
parametric search on A/D Converters. You can review the Vcc spec (you
will want 5V), interface type, number of bits and number of channels.
See http://www.analog.com/dynamic/parametric/scResultsDisplay.asp?
SearchType=PSS&ProductLine=ADC
Then it's time to study the datasheet until you fully understand how it
is going to work.
Richard
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