Preventing overvoltage on serial pin
Double check your HW specs on both ends. Many receivers will be tolerant to incoming voltages levels from the next "standard" voltage level, e.g. many 1.5V receivers will accept 1.8V signals, 1.8V will accept 2.5V, 2.5V will accept 3.3V, etc. If that's the situation you're in, you don't need level translators. Also, if that voltage "tolerance" isn't clearly spelled out, you can parse it out of the min and max V_IH, V_IL, V_OH, and V_OL specs of the two devices.