[NTLK] MP2x00 Internal Interconnect Breakout
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
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
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
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