Trouble using microstrain 3dm gx3 45 in ROS

edit

I'm using microstrain_3dm_gx3_45 package available for ros. I am always hung up at pinging saying checksum error. I noticed that the code for checksum is:

char b1=0;
char b2=0;

for(unsigned int i=0; i<arr.size(); i++)
{
 b1 += arr[i];
 b2 += b1;
}

arr.push_back(b1);
arr.push_back(b2);

I think there is an error as b1 and b2 should be u16. Anyways i have found other people using same package to connect. Is the problem somewhere else?