Simulink of arduino UNO R3 and ADXL335

Hi everybody
I am using Arduino UNO R3 in combine with ADXL335 in order to get real time data using simulink. I able to read serial port and plot it into scope.But in this case, I am getting constant y axis data in unit8 class data type. The value changes with time but still constant like (51 49 9) and its repetition with time. But the data should be like 512 510 520 or around that in three axis respectively. Any suggestion would be great help. The attached is my simulink model. It should be mentioned that I also tried all data class type.

Serial_port_data.mdl (24.4 KB)