Terastation Serial console
As we can see from the hardware page, the CPU offers two serial ports. The first one is used for the system console, but it's not accessable from outside the box. The seccond one is used to communicate with the XXX microcontroller.
But if we recheck the specs there is support for an UPS with serial port. And there actually is a serial port on the back of the box.
If we open the box, there is the serial connector:
Close to it is a level shifter to convert the 5v (or 3.3v) levels to RS232.
If we look closely the three, actually four, pins of the level shifter are connected to middle pin of the three connectors: JP3, JP4, JP5.
- Vcc, !SHDN
Inorder to connect the system console we must first remove the three zero-ohm resistor (R437, R440, R441) and move them to (R438, R439, R442).
Removing the SMD resistors already is a pain, so I decided to add three pin-heads/jumper.
Unforunately this does not yet work. We also have to bridge R76 to get input from the serial port to the CPU. Do not remove R75, it is a 10k ohm pull-down. If you remove it the input to the CPU will float and feed random junk to it, not what you want.