AVR-Chat

On Fri, Feb 25, 2005 at 10:12:30AM -0500, Phillip Vogel wrote:
> 
> In the simplest setting, you just use the drivers from ftdi, and the device
> looks like a com port on the PC. On the microcontroller end, it's an async
> serial device. Just hook it up to the tx & rx pins of your uart, set the
> baud rate accordingly, and it's running. Really couldn't be much simpler. 
> 
> Also, you may want to look at the modules from Lynx, which have the ftdi
> chip and all the glue in a 16 pin hand-solderable package. Just add a USB
> connector and you're good to go.

USB is the latest hot stuff and all that, and I admit that I'm not
paying full attention, but am a bit surprised not to see mention of
EIA/TIA-485. Its as simple as RS-232.

With any solution you'll have to devise a method of addressing the
specific unit out of the 16 proposed. Suspect via USB they will appear
in random order as pseudo-COM ports. Doubt you wish to code a full
Modbus protocol (http://www.modbus.org/) but the basics of a half duplex
one master many slaves are described in their documentation.

Some AVR boards such as the MAVRIC-II come with 485 hardware.

Ultra-cheap amateur radio operators used to build similar "diode matrix"
switches for AX.25 TNCs with common RS-232 interfaces. "It worked" was
the best one could say of that solution. Didn't scale well. Doubt it
would scale to 16 nodes.

-- 
David Kelly N4HHE, dkelly@HiWAAY.net
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Whom computers would destroy, they must first drive mad.