Re: [avr-chat] will an avr be fast enough...

[Galen Seitz]

Reza Naima <address@hidden> wrote:

> Thanks for all the info that I've recieved so far.  To clarify, I need
> 16x20khz sampling (20khz per channel).  I've looked at the datasheet for
> the MAX1031 part 
> 
> http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3872
> 
> and it's SPI protocol seems quite odd compared to all the other devices
> I used.  It looks like you can initate sampling, wait some time, then
> read from all the channels sequentially (mode 00).  Assuming I can get
> the data into the AVR via SPI at the required speed, I am then open to
> implement any type of IR communications, and I'm not forced to stick
> with a 38khz modulated IR signal.  There are receives that work at
> higher frequencies, and will investigate if I can simply do something
> like manchester encoding and transmit the data directly (adding a
> checksum along the way).  The receiver will be in close proximity to the
> transmitter, and I'm hoping that it can be configured such that it will
> not recieve any ambient light.
> 
> If samples are corrupt, it's not a big deal as long as the checksum
> indicates it as being corrupt.  And the signals are changing quite
> rapidly so simple compression schemes (like only sending data when the
> signals change) is not a viable option.  However, the data of interest
> is will only last a few hundred ms, so one option is to add ram, cache
> the data, and then transmit at a slower rate.
> 
> The tricky part is that the entire circuit needs to be about the size of
> a quarter, and as thick as two quarters.  This includes an amplifer, the
> A2D, an AVR or some sort of CPLD/FPGA, the IR mechanism, as well as
> whatever power conditioners required (power is transmitterd inductivly
> to a coil that will wrap around the circuit).

Have you considered using one of the Atmel ARM7 parts?  The AT91SAM7S
series has a bit more processing power than anything in the AVR line,
and the pricing that I've seen is very aggressive.  I haven't looked at
the MAX ADC you mentioned, but the AT91SAM7S has a peripheral DMA
controller that might make it possible to bring the ADC data in or send
IR data out in the background.  As far as size goes, the AT91SAM7S32
comes in an LQFP48 which is 7x7 mm.

galen