Let's Make Robots!

serial uart with only rx or tx not both

Can I deliver serial data from one direction to enother (2 mcu) only with tx :

MCU1                                       MCU2

      TX<-------------------------------------<RX

 

?

Components to put bw 3.3v signal and 5v

I have an Arm based platform with Serial UART interface but in 3.3v level.

I want it to communicate with my Arduino.

I have a 3.3v power source in the Arduino(Dumilinove).

My question is what components to put between the 3.3v platform RX/TX and the Arduino RX/TX ?

Item similar to Ping))

found this item in ebay:

http://cgi.ebay.com/Ultrasonic-Sensor-for-Robots-Security-System-D-Robotics_W0QQitemZ140359202261QQcmdZViewItemQQptZUK_BOI_Electrical_Components_Supplies_ET?hash=item20ae0f75d5

is it similar to Paralaxx Ping))?  because with shipping it dramatically less expensive then  Paralaxx Ping)).