This is a simple Hello World program using a serial LCD on the mbed Dev Board.
Login to your account at the mbed website.
Import this serial_lcd program into your online compiler. Compile and download to the mbed device. Press the Reset Button and the Hello World text should display on the LCD.
Troubleshoot
If no text is displayed check data is coming out on pin 3 of connector X2. This can be done using a scope or a logic analyzer, put the probe on pin 3 (white wire).
Using the Saleae logic analyzer, connect the grey wire to GND. Red wire (CH2) to RXD.
Saleae Logic Analyzer connected to Serial LCD
Setup the analyzer for capturing, press the Reset button on the mbed. The waveform should look like below.
Waveform showing Hello World transmitted to serial LCD