[NTLK] Internal WiFi Project

Matthias Melcher mm at matthiasm.com
Sun Apr 17 12:30:01 EDT 2016

> On Apr 17, 2016, at 5:05 PM, Jake Bordens <jake at allaboutjake.com> wrote:
>> If that was all there is, then why should the SER-001 override the LTC on the main board? If no SER is installed, the internal LTC connects vie the cable and all is fine. If the SER is installed, it seems to get priority over the main board LTC without any user action. But how? 
> I just checked with a meter, the SER-001 board routes the SerPortSel0 signal directly to the shutdown pin on the SER-001's LTC.  Based on this, it seems to me that the board does not actually obey the SerPortSel pin, rather it duplicates the same circuit on the MLB.  I'm not sure how this works specifically, because that means you could have two drivers on the same RX pin.  Maybe they're open collector or something I don't know.

"When high, the internal serial Device can drive serial port 0". SHDN is non-iverting, so setting it high indeed shuts down the chip. It seems that both LTCs are active at the same time if all of the above is correct. That would generate a conflict on RX. I did not see anything saying that RX is special.

The conflicts would be on RXD) RX0 and ~RX0 (Pins 11, 10, 9). I do not see anything special about those outputs. They should be CMOS level.

Can you check the level of SerPortSel0 during data transfer? In a perfect world, it would be low when transmitting data through the external port, and high when transmitting through SER-001. If it is low in both cases, then yes, we have conflicting outputs.

> Did you try running something like:
> 	AddArraySlot(GetGlobals().ModemLocations, {title: "Modem", id:"mdem"});
> 	AddArraySlot(GetGlobals().ModemLocations, {title: "Extra", id:"tblt"});
> I've got a little pkg that runs these lines in the InstallScript. (For a limited time) you can find here:
> 	https://dl.dropboxusercontent.com/u/1704518/Modem%20Enabler.pkg

I am aware that switching those ports is a one-liner. My hope was, that the internal module could run without any driver whatsoever installed, so that a virgin MessagePad can be brought to life by simply plugging the module in.

I am starting to thing that it is easier to build a PCMCIA module from scratch (ok, kidding).

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