False data received through serial port

Hi,

I'm working on controlling linear actuator with Matlab through serial port. It has seemed to be working right. But recently I've got some problem.

fwrite(port,[1 60 0 0 0 0]);

bpos1=fread(port,6)'

The above is to ask actuator the reply the current position and actuator supposed to reply its current position right away. After writing fwrite, I can get reply from actuator by using fread func. Eventually I get the right reply, but before receiving that right value, it replies wrong value for several second.And I keep entering fread till get the right value. It sometime takes few second or more than 10 second.

So to figure this out, I did some cable work and connected the cable to second computer at a time and looked at the date coming out from actuator by using serial terminal software. And in first computer I saw wrong value, but in second computer I couldn't see any wrong value. i.e, actuator replies right value. Than problem is on somewhere in computer side. I changed the serial-usb adapter and it didn't work. So the reason of this issue I'm thinking is

1. due to using serial-usb adapter 2. Matlab

I'll try 1 with other computer which has serial port. But regarding Matlab, I can't seem to find any reason.

Following is whole the function I use to get the current position data from actuator. Almost same as above.

function[pos]=CurrentPos(port)

fwrite(port,[1 60 0 0 0 0]); %-> To ask actuator to reply back the current position

bpos1=fread(port,6)' %-> store the replied data.

bpos2=bitsToNumber(bpos1(3),bpos1(4),bpos1(5),bpos1(6));

bpos3=MicroToMil(bpos2);

pos=floor(bpos3)+1; % last 3 lines are to convert bit to number.

I asked actuator manufacturer and they were not sure, but mentioned that it might be some buffer problem of Matlab.

Could anybody help me?