Hi, have you crossed over the tx and rx, so that the tx of arduino unit is connected to the rx of the sinsmart, and rx of the arduino unit is connected to the tx of the sinsmart.
As well as the gnd of both units connected together.
Can you please post a copy of your sketch, using code tags?
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png or pdf?
Tom...... 