|1||Vpwr||Roomba battery + (unregulated)|
|3||RXD||0 – 5V Serial input to Roomba|
|4||TXD||0 – 5V Serial output from Roomba|
|5||DD||Device Detect input (active low) – used to wake up Roomba from sleep|
|6||GND||Roomba battery ground|
The RXD, TXD, and Device Detect pins use 0 – 5V logic, so a level shifter such as a MAX232 chip will be needed to communicate with a Roomba from a PC, which uses rs232 levels.