diff --git a/hgdriver/hgdev/hg_scanner_200.cpp b/hgdriver/hgdev/hg_scanner_200.cpp
index 58363ea..2e701ca 100644
--- a/hgdriver/hgdev/hg_scanner_200.cpp
+++ b/hgdriver/hgdev/hg_scanner_200.cpp
@@ -290,8 +290,11 @@ int hg_scanner_200::start(void)
 	}
 	
 	USBCB usb = { setting3288dsp::START_COMMAND, img_conf_.scannum, 0 };
-	ret = writeusb(usb);
-	io_->set_timeout(500);
+	{
+		std::lock_guard<std::mutex>      lock(io_lock_);
+		ret = writeusb(usb);
+		io_->set_timeout(500);
+	}
 	VLOG_MINI_1(LOG_LEVEL_WARNING, "write start command = %s\n", hg_scanner_err_name(ret));
 
 	if(ret == SCANNER_ERR_OK)
@@ -311,8 +314,10 @@ int hg_scanner_200::stop(void)
 	int ret = SCANNER_ERR_OK;
 
 	USBCB usbcb = { setting3288dsp::STOP, 0, 0};
-	ret = writeusb(usbcb);
-
+	{
+		std::lock_guard<std::mutex>      lock(io_lock_);
+		ret = writeusb(usbcb);
+	}
 	user_cancel_ = true;
 	if (ret == SCANNER_ERR_DEVICE_BUSY)
 	{
@@ -972,7 +977,12 @@ int hg_scanner_200::set_auto_flat(int data)
 {
 	USBCB usbcb = { setting3288dsp::START_FLAT,data,0 };
 	int len = sizeof(usbcb);
-	int ret = writeusb(usbcb);
+	int ret = SCANNER_ERR_OK;
+	
+	{
+		std::lock_guard<std::mutex>      lock(io_lock_);
+		ret = writeusb(usbcb);
+	}
 
 	if (ret == SCANNER_ERR_OK)
 	{