Re: 8 channel E*G with AVR and bluetooth

On Wed, Jan 22, 2014 at 12:52 AM, Stefan Jung <[email protected]>wrote:

> Grant
>
> I hope you realize that you need to use at least a 4-layer PCB for such a
> design.  A high density IC such as the ADS1299 needs at least a solid
> ground plane and a dedicated +3V3 plane or a mixed power only layer would
> also be a good idea.
>
> You cannot run the micro and a sensitive device such as the ADS1299 from
> the same regulator without at least using some inductors and low ESR caps
> to separate the noisy micro (switching noise) from the V-analog supplies of
> the ADS.  Otherwise use two regulators. One for digital and one for analog
> supply lines.
>
> I personally would rather use a 16-bit or even an entry level 32-bit
> processor.  I am sure the ATMega168 will be sufficient but the cost
> difference these days is so small, it approaches nil.  I use Microchip and
> don't know the Atmel products.  I do know that Atmel makes good stuff that
> is arguably better than similar PICs.  But coming from the PIC world, 8-bit
> processors are usually limited to the number of UARTS, SPI modules etc.  I
> would think that this is also true in the ATmega world.  With 16/32 bit
> processors you should be able to upgrade to bigger RAM/ROM devices in the
> same footprint should you decide to do more fancy software at a later
> stage.   But as I've said, that's just a personal view.
>
>
4 layer and separate AVSS/AVDD/DVDD supplies are planned.  Some of the
larger megas have 4 UARTS, multiple SPI, etc...but this project really only
needs one uart and one spi.  At least it isn't the good old days when half
of the AVRs required a software uart.  : )

I tried to keep the project creep low by using a simple processor.  I also
didn't plan on any provision for daisy chaining multiple chips together.  I
had to keep the processor consumption down to run all of my LEDs!

A second ATmega2560 will most likely do the heavy lifting and be connected
to the wii remote, accelerometer, gyro, magnetometer, and air pressure
switch (sip and puff).

Grant

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