You can perform bi-direcitonal serial by using the i2c interface and a serial interface, such as an arduino.

ok,just looking at a cheaper way,without I2C interface,on the D0 pin is transmitiing but the next pin on cpu is received ,but you are using it for something else

Any way it can be changed,one very good reason to have both receive and transmitt codes from the roomba ,like reading the sensors and more

Besides other boards can use the TX and RX pins

We have a specification for an i2c serial adapter. However there will never be native support for serial input on the ezb natively. It will require an add-on.

DO you have the name or model of the I2C serial adapter,when i get back in 3 weeks i hope to order one

Again, we will have it - we do not have it right now. We are in the middle of designing it and a few other things. :)