[NTLK] MP2x00 Internal Interconnect Breakout

Matthias Melcher mm at matthiasm.com
Mon Jan 5 04:11:03 EST 2015

> On Jan 5, 2015, at 2:37 AM, Jake Bordens <jake at allaboutjake.com> wrote:
> He has code to toggle the DIO pin for Serial 3.   What's interesting to me 
> is that the ROM actually has two functions already:
> 0x0026d050	SerialPort0LineDriverConfig__16TVoyagerPlatformFUcT1	
> 0x0026d094	SerialPort3LineDriverConfig__16TVoyagerPlatformFUcT1	

Seems like I have to dive into the ROM ;-)

> SerialPort0 uses a GPIO while SerialPort3 uses a DIO for toggling the 
> enable pin.   I'm hoping that I can call these "LineDriverConfig" 
> functions to do what I need rather than the DIO/GPIO functions directly, 
> as Ekhart does.
> For serial3, my impression is the SerPortSelect pin doesn't do much.  I 
> think you can drive port 3 regardless of what this pin says, from either 
> the internal or external location.  You're just not being a good citizen, 
> and a well designed peripheral will honor the state of this pin.  Port0, I 
> think its a little more important because of the LTC line driver IC.  I 
> think the SerPortSelect pin in this case shuts down the driver for the 
> external port, preventing a conflict with the device on the internal port.

The SerPortSelect is an output pin (from the main board to the originally planned modem card). The documentations say that this pin can be used to enable an internal communication on Ser1 and disable the external driver. SER-001 does that and it works - but how does it work?

SerPortSelect is an output. I assume that this pin goes low (high?) for a few cycles to test if a modem card exists. During those cycles, the modem card must pull some other line low (or high?) that was previously high impedance (or high, or low?). Question iss, which line(s), and what logic. I took a good look at the SER-001, but I could not figure it out. And again - it did work once for me, but I could not repeat it! Dang it!

The wonderful advantage is, that no software changes whatsoever is needed on the MP. That is great news for MPs without software to get around the hen/egg problem when using a wifi card.

> I'll keep you posted.  I got side tracked with an eMate that I bought... 
> But I'll get back playing with the wifi project soon.

Please do. No hurry though, as I still have this thing, um, called job, that keeps from hacking the MP full time ;-)


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