[NTLK] MP2x00 Internal Interconnect Breakout

Matthias Melcher mm at matthiasm.com
Tue Jan 13 16:56:34 EST 2015

> On Jan 11, 2015, at 10:55 PM, Jake Bordens <jake at allaboutjake.com> wrote:
> I did some testing.  Interestingly, Serial3 does work at 119200 even 
> though the N2 platform docs clearly state that the maximum is 38400.  
> There are some cut and paste errors in the document, but it seems like 
> they explicitly changed the speed when they copied the paragraph from the 
> previous section.

Wow, quite fast.

> Similarly, Serial0 should work at 230400 based on the docs, but it does 
> not.  When I attempt to connect at this rate, it actually connects 119200. 
> This is the same for Serial3, it just silently fails and rolls back to 
> 119200... So its a little disappointing that I can't get that 230.4k speed 
> to work.

Maybe they initially planned different hardware, but figured that using the same gates for all three serial ports makes more sense. Just wild guessing.

In the N2 docs, they also describe that Ser1 can work much faster in synchronous mode. I wonder if that was ever implemented.

> In looking at some pictures of the USB-001, it looks like there is an 
> unpopulated resistor (R1) that would connect the SerSelect3 pin up 
> somehow.  So I think, based on this, it doesn't really care what the 
> motherboard is signaling-- but its hard to be sure, given I don't actually 
> have one of the boards.

I assume that for Ser3, there is no need to check the signal. What is the likelyhood of someone connecting a mode and an internal USB card at the same time? As you say later in the text.

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