libftdi Archives

Subject: RE: Some realizations about the FT2232D...

From: "Michael Plante" <michael.plante@xxxxxxxxx>
To: <libftdi@xxxxxxxxxxxxxxxxxxxxxxx>
Date: Mon, 30 Aug 2010 13:48:17 -0500
John Oyler wrote:
>> On Aug 30, 2010, at 11:18 AM, Michael Plante wrote:
>> >
>> > Also, something I meant to mention before:  as long as you're having
>> > with synchronization in MPSSE and don't have time to code up all the
>> > needed to maintain sync, I'd suggest you try increasing your latency
>> > to something high just to get started.  Like maybe the default of 16.
>> > that works, you can always turn it back down later.
>> 16 did nothing... would still do about 2 reads before I got the answer
from the
>> first. Knocking it up to 64 did improve things, answers always seem to
sync up
>> with commands. Not sure if I want to leave it there or not, it's visibly
>> On the other hand, I'll only ever be reading signal strength out of the
>> register anyway, so I might. Will have to see how much it affects things.

Given this, I'd suggest one of two approaches (with the same end goal):

1) build everything bottom-up cleanly, like I did, and never set a high
latency timer


2) get some basic code working with a very high latency timer (sounds like
64 might be good.  think the max is 255), and then insert all your sync code
later when you want to speed things up

I wouldn't suggest leaving the latency timer high forever, because that's
not a solid fix.  I mentioned it just to get you off the ground, if

>> answers always seem to sync up  with commands.

You might also try the "send immediate" byte, and see if answers pop up when
you send that, too.  I don't remember.


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