[sdiy] PIC help

[Jerry Gray-Eskue]

Scott,

Here are a few of my first thoughts:


<<My current project is a programmable filter bank...
.. dsPIC33FJ128GPxxx series >>

If you are building a Digital Filter system you may want to use one of the
dsPIC Digital Signal Controllers they have the DSP extras. Another major
decision point is through hole or surface mount part.

<<a. 10 (at most) analogue inputs for reading pots, 10 bit ADC would be
fine
b. a few digital inputs for reading switches and pushbuttons>>

Any number of the PICs can do this.

<<e. ability to hook up an LCD display (2 line by 40 character or smaller)>>

Some of the PICs have LCD support built in, or you can use secondary LCD
modules.


<<3. Some of the dsPIC chips have a built-in 16-bit DAC but it appears
to be best suited for two channels of audio, not for 24 channels of
control voltages. Would I be better off using an external DAC to get
24 analogue outs and avoid the internal DAC? >>
<<4. If using an external DAC, is there any advantage to using one DAC
with lots of multiplexing to get 24 outputs vs. using several 8-
channel DACs (e.g. TLV5610)?>>

You can use them, but that only gets 2 channels of analog, you could try
using these or other DACs  multiplexed with sample and holds, but this can
be twitchy to get right. several external DACs may be the best bet. There
will be cost / design effort / performance trade offs with any solution.


<<5. It seems that dsPIC chips don't have enough built-in EEPROM to
store all the info I want for the presets. Is it best to avoid trying
to max out the internal EEPROM and use an external EEPROM? (I see that
Seb has hooked up an EEPROM to his Digi-Mod.)>>


You may also be able use some of the FLASH memory especially if these are
factory presets.
It also may be possible to reduce your data set size without losing any
information. This gets complicated but techniques used in data compression
can be used in a simplistic manner with excellent memory foot print
reduction.

If you still need more space Microchip has several serial memory devices
that may help.



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