Solution:

Here are some suggestions for your reference when you use ADAM-4550: 1. Transmit a big package from master ADAM-4550 ( transmitter) to slave ADAM-4550 (receiver): A: You'd better set baudrate of Master 4550 lower than slave 4550's in order to avoid overrun error. 2. If RS-485 side of ADAM-4550 is not used, should Data+ and Data- pull high and low respectively? A: In order to avoid interference from RS-485, you need to pull DATA- to GND through 10K ohmn, but it is not necessary to pull high for DATA+ because we did it in PCB.