[En-Nut-Discussion] high speed serial

[Nic Cave-Lynch]

Hi Jeremy,

without knowing the details of what you're wanting to do, or the serious 
details of the internals of Ethernut, I'd guess you were pushing the 
proverbial up hill. It looks like the timing's likely to be against it, 
by the time you add in the Ethernet interrupt latency, re-framing for 
Ethernet, bashing the frames out to the Ethernet chip, and OS overhead.

Are you wanting to get data in to a PC? If so, the approach I'd take 
would be a little bit of custom hardware based around one of the USB 
chips from FTDI (http://www.ftdichip.com/Products/FT2232C.htm). They're 
as simple as it gets, and will run up to 1 Mbaud, with a trivial PC 
interface, and drivers for Linux. And they say they'll do 3MB if it's a 
TTL interface.

Alternatively, I've done 250kb with an 8MHz clock to Ethernet frames, 
but only UDP, and writing most of it in assembler (it was actually 
fairly easy if you don't want to be too standards-compliant)

But, as I say, I don't know the guts of the Ethernut well enough to know 
if it would cope: I'm only guessing that the chip's processing power is 
such that you've got little chance of success, and none at the higher 
bit rates...

Good luck

Nic C-L


Jeremy.Thompson at csiro.au wrote:
> Hi,
> 
> I am having a problem using an ethernut 2.0 rev A when communicating
> with a high speed serial device.  The rate I am attempting to
> communicate on is 500000 baud and it appears that data is being
> overrun/lost during the transmission.  The ethernut has been modified
> with a 16 Mhz crystal to allow for communication on the higher then
> standard baud rate.  I am using uart0 and the data is "packetized" into
> chunks of about up to 1.2kb and is streaming continuously.
> 
>  
> 
> My main question is can the ethernut communicate on this rate
> successfully? As the data being transmitted is checked using CRC even
> the loss of a single byte is bad news and will result in the loss of a
> complete data packet.  I have tested this application using lower baud
> rates and have had no problems.  If the ethernut can handle 500000 then
> I will focus on optimising and tuning my application but if not then I
> might have to find another solution.  Also in the future I may be
> looking at trying to interface with a 1500000 baud device.
> 
>  
> 
> Cheers
> 
> Jeremy
> 
> 
> 
> 
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