OT3m vs T3-mini
I've a question regarding the serial ports on the T3 family.
In the OT3m circuit here
I can see serial ports A & B pass through a MAX232 so that the voltage level is buffered and inverted.
Looking at a board of a T3-mini, I can't see any MAX232 or equivalent there, although there are a couple of
transistors in roughly the right places (Q1 & Q3), but insufficient to do both tx and rx on two serial ports.
Seeing as the code (as far as I'm aware) is the same between the OT3m and T3-mini, how do you ensure the logic
polarity is the right way up for both versions?
The reason why I ask, is that I'm having trouble getting the T3-mini and the config program to communicate
via Serial Port A. It works fine via the USB port though.
I've tried 3 computers with real serial ports, and 2 different brands of USB<->RS232 adapters, all with a
lack of result via the config program. These same ports and adapters talk fine to a Tinytrack and an OT1, so
I'm pretty sure they are ok.
Using a scope, I can see the Config program serial data reaching A_RX on the T3-mini, and a response is coming
back out A_TX, reaching all the way down to the DB-9 I've attached via a lead.
I know I have my DB-9 pins correct as the serial data is getting to the T3-mini.
I have been toying with the idea of adding an inverter and a MAX232 in the serial out lines, but thought it
worthwhile checking first about T3 serial circuit differences.
P.S. a schematic of the T3-mini might help & would be appreciated.