[clug] Serial communications between Atmel processors

Paul Wayper paulway at mabula.net
Sun Nov 16 13:51:20 MST 2014

Hash: SHA1

On 16/11/14 13:30, Alex Satrapa wrote:
> On 16 Nov 2014, at 10:52, Paul Wayper <paulway at mabula.net> wrote:
>> Anyway, now to find out how fast they can communicate, and how many I
>> can have talking in a string...
> You’re going to need a specialised interface for that. Options include
> RS485 which is designed as a serial bus, I2C, SPI, or even ZigBee.

All this needs is A -> B -> C -> .. -> A in a unidirectional string.  In the
final thing 'A' will be the central monitor and will collect data from
multiple strings.  It also needs to be opto-isolated because each board will
have a different ground.

The answer was 4 - mainly because I couldn't be bothered hooking up the
wires on the breadboard for five.  It's weird - two ticked over nicely,
three was pretty reliable but occasionally stopped, four would see several
micros spend about half the time in the 'waiting' state, despite putting
delays in the code.

That's a problem for another day.  I've now got the basic circuit for the
actual capacitive switching, and will try it out when I feel brave.  The
code runs (and runs deliberately slowly), LEDs turn on and off; I just need
to check the capacitor and get the courage to hook the second cell in...

Have fun,

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