[Cryptech Tech] Noise board on Novena

[Benedikt Stockebrand]

Hi again,

Bernd Paysan <bernd at net2o.de> writes:

> For things that connect to a PC, however, I prefer UART, because USB to serial 
> is very cheap and easy to get (and supported out of the box by the OS), 

...if we're talking FTDI chips, yes.

> whereas USB to SPI requires a specific FTDI device and a special library.  

FTDI has something like that?  I've only found the Microchip MCP 2210
for that job.  But yes, one of the reasons why so far I've stayed away
from them is that they need a suitable driver (kernel or userspace,
whatever).  At which point I decided I'd rather consider the USB capable
PICs instead and do away with that extra chip altogether---maybe next
year...after I've made myself comfortable with FPGAs, of course...

> When I use UART protocols, I make sure that the first byte you will send over 
> the UART is odd, so the device can do automatic baud rate adjustment (like 
> "AT" modem commands - 'A' is odd: 65).  UART has the advantage of needing just 
> two lines (RX and TX; when you talk to hardware, you don't need flow control, 
> the hardware will always be fast enough to respond), and there's no mode 
> inflation (when you use 8N1).

Well, there's the issue with the speed; if you use automatic baud rate
detection then you have to make sure you discard that first bit.

And as far as flow control is concerned: I actually kind of use that
with the arrgh board.  Eventually it might be useful to shut down the
step-up converter and save some power.  But of course that's an optional
thing, and I'm not even sure I want that extra complexity anyway.


Cheers,

    Benedikt

-- 
Benedikt Stockebrand,                   Stepladder IT Training+Consulting
Dipl.-Inform.                           http://www.stepladder-it.com/

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