IMU and rosserial

edit

Hello,

I'm using the arduino with rosserial and my code is the simplest one possible :

#include <ros.h>
#include <ros/time.h>
#include <sensor_msgs/Imu.h>

ros::NodeHandle  nh;

sensor_msgs::Imu imu_msg;
ros::Publisher pub_imu( "/imu", &imu_msg);
char frameid[] = "/imu";

void setup() {  
Serial.begin(57600);

nh.initNode();
nh.advertise(pub_imu);
imu_msg.header.frame_id =  frameid;
imu_msg.header.stamp=nh.now();
}


void loop() {

 pub_imu.publish(&imu_msg);
 nh.spinOnce();
}

And when I run it, I have that kind of error :

[INFO] [WallTime: 1395754919.360506] ROS Serial Python Node
[INFO] [WallTime: 1395754919.372573] Connecting to /dev/ttyUSB0 at 57600 baud
[INFO] [WallTime: 1395754921.671875] Note: publish buffer size is 280 bytes
[INFO] [WallTime: 1395754921.672177] Setup publisher on /imu [sensor_msgs/Imu]
[ERROR] [WallTime: 1395754921.673737] Message from device dropped: message larger than buffer.

So I can see that the message is considered too big by the PythonNode but it's empty and I'm using the standard IMU message. I'm using the Arduino duemilanove. How can I reduce the size of the message ?

[EDIT]

After some test, it mostly come from the fact that it's an IMU message. If I use a range type for example, it works. Is it just impossible to send IMU message type through libserial ? Should I use 3 Publisher to transport the message and create a node that send a Imu_msgs type after ?

Thanks a lot.