mini2440 wince下 serialPort1_DataReceived始终进不去

[东东un]

我是用控件打开serialPort1的。
private void button1_Click(object sender, EventArgs e)
{
serialPort1 = new SerialPort();
serialPort1.PortName = "COM1";
serialPort1.Open();
}
然后通过PC的串口调试助手给mini2440发的数。
可是serialPort1_DataReceived就是触发不了。
private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{

if (serialPort1.IsOpen != true)
{
serialPort1.Open();
}
string str = serialPort1.ReadLine();
fl_num.Text = str;
}