Solution:

The common factors causing the data loss problem is shown as follows: 1. Remove "printf" command : Actually, if you use "printf" command under ADAM-4500/5510, then ADAM-4500/5510 will "print" something on your screen through debug port (COM3), it is different from general PC because general PC always provides a monitor, but ADAM-4500/5510 must use com port to show something on another screen , it will take some time. At the moment, something is coming from your COM1 or COM2, then it could cause data loss. You are recommended to remove "printf" command which shows something on the screen during normal communication, just leave "printf" command which inform you when error is occurred. 2. Enable interrupt function : Using ISR to handle receiving data can avoid data loss. 3. Change "outport" to "outportb" : "outport" command is for a word, but we just handle one byte, if possible, please change "outport" to "outportb"