[NTLK] Internal WiFi Project

[Matthias Melcher]

> On Apr 17, 2016, at 11:35 PM, Matthias Melcher <mm at matthiasm.com> wrote:
> 
> 
>> On Apr 17, 2016, at 8:23 PM, Jake Bordens <jake at allaboutjake.com> wrote:
>> 
>>> 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.
>> 
>> I'll do this test... But I just did another test which seems to confirm that both LTC's are active when using a SER-001.
>> 
>> I can swap the DIN connector (Apple Serial to RS-232 cable) from the SER-001 to the Dock Connector adapter and both work at the same time.  This was with PT-100.  I could both transmit and receive on both ports without disconnecting the connection in PT100 (or on the host PC).
> 
> Well, I guess that already clarifies it.
> 
> I just traced the routes on the PCB and there is nothing special about it. All TX and RX lines are connected together just as the SHDN lines of both LTC. No inverter between those two, so, yes, they are shorting out three times two outputs.

Ok, I got some news from a forum focused on electronics. According to on author, the "default" level of RX0 and friends is somewhat high impedance. It doesn't say so directly in the data sheet, but he derives this information from "Figure 13. Receiver Enable and Disable".

This would explain why SER-001 works without needing a driver or special setting. This would also allow any internal card to run in parallel to the interconnect driver and simply "inject" data into the serial data stream without damaging the internal driver chip.

In conclusion, I will set up a breadboard wiring and hopefully connect to the Wifi chip some day this week.