struct error

[tiesus]

When i read the a1 package from an OpenImu300RI connected via a rs232toUSB converter, the driver throws approximately every second start the following error:

ROS DISTRO: noetic
Device: OpenIMU300RI 5020-3309-01 03.01.08 Firmware: VG_AHRS_J1939 03.01.09

Traceback (most recent call last):
File "/catkin_ws/src/ros_openimu/scripts/openimu_driver.py", line 57, in <module> readback = openimu_wrp.readimu()
File "/catkin_ws/src/ros_openimu/scripts/openimu_driver.py", line 34, in readimu readback = self.openimudev.getdata('a1')
File "/catkin_ws/src/ros_openimu/src/aceinna/tools/openimu.py", line 65, in getdata time_ms = struct.unpack('I', bytes(readback[0:4]))[0] #unin32
struct.error: unpack requires a buffer of 4 bytes