[NTLK] MP2x00 Internal Interconnect Breakout

Jake Bordens jake at allaboutjake.com
Sun Jan 11 16:55:10 EST 2015

>Yeah, you may still be able to double that for ser0. OTOH, we already 
>have timing issues with ser0 when using the regular serial protocol. 
>You'd probably reach the end of what the DMA/Interrupt/Buffer setup of 
>the serial port can handle. PCMCIA is at a great advantage here because 
>it can map directly into memory.

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.

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.

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 have added "mdem" to my "GetGlobals().ModemLocations" to make SerPort3 
available to apps.  The OS does not seem to toggle the SerPortSel3 pin, 
though.  I think I knew this and am re-learning.  This is the purpose of 
Ekhart's code on github, to manually toggle the pin and properly select 
the internal port.

This is probably all academic, as I don't know of any external 
interconnect accessories that use Serial3, so there should never be a 
conflict.  Even if there are any, they are probably very rare and could be 
avoided easily.


More information about the NewtonTalk mailing list