add and export function to send only a null frame

diff --git a/hmcfgusb.c b/hmcfgusb.c
index 1ba9b2412a7b2b5b685faef7beb73f6c71def49e..ce8c595268918381544c756d60f3b36d0045ae5f 100644 (file)
--- a/hmcfgusb.c
+++ b/hmcfgusb.c
@@ -140,6 +140,20 @@ static libusb_device_handle *hmcfgusb_find() {
        return NULL;
 }
 
+int hmcfgusb_send_null_frame(struct hmcfgusb_dev *usbdev)
+{
+       int err;
+       int cnt;
+
+       err = libusb_interrupt_transfer(usbdev->usb_devh, EP_OUT, NULL, 0, &cnt, USB_TIMEOUT);
+       if (err) {
+               fprintf(stderr, "Can't send data: %s\n", usb_strerror(err));
+               return 0;
+       }
+
+       return 1;
+}
+
 int hmcfgusb_send(struct hmcfgusb_dev *usbdev, unsigned char* send_data, int len, int done)
 {
        int err;
@@ -159,9 +173,7 @@ int hmcfgusb_send(struct hmcfgusb_dev *usbdev, unsigned char* send_data, int len
        }
 
        if (done) {
-               err = libusb_interrupt_transfer(usbdev->usb_devh, EP_OUT, send_data, 0, &cnt, USB_TIMEOUT);
-               if (err) {
-                       fprintf(stderr, "Can't send data: %s\n", usb_strerror(err));
+               if (!hmcfgusb_send_null_frame(usbdev)) {
                        return 0;
                }
        }

diff --git a/hmcfgusb.h b/hmcfgusb.h
index 8a0751a1bcfa7b5b5f11ed555369138abbb6c984..e50f831459900996aeca2ea4629ee8d3de0c6d3e 100644 (file)
--- a/hmcfgusb.h
+++ b/hmcfgusb.h
@@ -32,6 +32,7 @@ struct hmcfgusb_dev {
 };
 
 int hmcfgusb_send(struct hmcfgusb_dev *usbdev, unsigned char* send_data, int len, int done);
+int hmcfgusb_send_null_frame(struct hmcfgusb_dev *usbdev);
 struct hmcfgusb_dev *hmcfgusb_init(hmcfgusb_cb_fn cb, void *data);
 int hmcfgusb_add_pfd(struct hmcfgusb_dev *dev, int fd, short events);
 int hmcfgusb_poll(struct hmcfgusb_dev *dev, int timeout);