AVR-Chat

This an email that Craig Limber sent to our robotics list, commenting on the
suitability of the Butterfly as a robot controller:

Hi there;

I've been doing some analysis of the AVR Butterfly to see what
usefulness it might be as a robotics controller and thought I would
share the results with everyone.  Everything I found I got from the
schematics in the butterfy's userguide I downloaded from Atmel.

The big thing I was looking for was useful I/O pins, especially
I/O pins with analog to digital converters or pulse width modulation
channels.   

Two 8-bit ports (with associated I/O pins) have connectors that we
can get at: port B and port D.  Unfortunately, those ports are
shared with lots of other stuff.

All four PWM channels are either shared with the navigation switch or
the piezo speaker.  We are stuck with the speaker unless we disconnect
it.  If we want to use the remaining PWM channels we just have to make
sure that no stupid humans fiddles with the button at the same time.

The rest of port B is shared with the ISP port (which isn't a big
deal as long as we use those pins for input only), the navigation
switch or the dataflash.
 
Port D also has a connecter but those pins are shared with the LCD.
According to the schematic they are connected but I am not sure
if the LCD actually uses them.  I will probably hook soemthing up
to see if signals are being sent when the LCD gets used.  If they
are used by the LCD then that entire port will be unuseable unless
the LCD is turned off.

However, all is not lost.  There are 4 pins on the JTAG port that
are useful (PF4-7).  They are also ADC channels.  That's cool.
 
The USI interface is also open for us (pe4-6).  The other ports
such as the USART have some circuitry in between making it less
likely we can use them for anything else.  
 
So, basically, we aren't left with many ports for other stuff.  
However, it's still a bargain for the cost and what you get.

I have a little table that shows the pin pin mappings.  

http://members.shaw.ca/climber/avrbutterfly

climber

-----Original Message-----
From: chrltn101 [mailto:chrltn101@yahoo.com] 
Sent: March 9, 2004 1:18 PM
To: AVR-Chat@yahoogroups.com
Subject: [AVR-Chat] Butterfly


Hi all,

I was thinking about buying a butterfly, but before doing so I wanted to
ask around and see what kind of reputation the board has (ie. does it
actually do what the data sheets say it supposed to do, what kind of
hinderances you ran into)

All comments/recommendations greatly appreciated,

-John



 
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