3 files changed, 35 insertions, 19 deletions
diff --git a/os/hal/include/serial_usb.h b/os/hal/include/serial_usb.h
index 104375391..25ce4859b 100644
--- a/os/hal/include/serial_usb.h
+++ b/os/hal/include/serial_usb.h
@@ -92,10 +92,6 @@ typedef struct {
    * @brief   USB driver to use.
    */
   USBDriver                 *usbp;
-  /**
-   * @brief   USB driver configuration structure.
-   */
-  USBConfig                 usb_config;
 } SerialUSBConfig;
 
 /**
diff --git a/os/hal/src/serial_usb.c b/os/hal/src/serial_usb.c
index fc082b56b..f05c341fc 100644
--- a/os/hal/src/serial_usb.c
+++ b/os/hal/src/serial_usb.c
@@ -223,7 +223,6 @@ void sduStart(SerialUSBDriver *sdup, const SerialUSBConfig *config) {
   config->usbp->param = sdup;
   sdup->state = SDU_READY;
   chSysUnlock();
-  usbStart(config->usbp, &config->usb_config);
 }
 
 /**
@@ -245,7 +244,6 @@ void sduStop(SerialUSBDriver *sdup) {
               "invalid state");
   sdup->state = SDU_STOP;
   chSysUnlock();
-  usbStop(sdup->config->usbp);
 }
 
 /**
@@ -322,12 +320,23 @@ void sduDataTransmitted(USBDriver *usbp, usbep_t ep) {
        so it is safe to transmit without a check.*/
     chSysUnlockFromIsr();
 
-    usbPrepareQueuedTransmit(usbp,
-                             USB_CDC_DATA_REQUEST_EP,
-                             &sdup->oqueue, n);
+    usbPrepareQueuedTransmit(usbp, ep, &sdup->oqueue, n);
+
+    chSysLockFromIsr();
+    usbStartTransmitI(usbp, ep);
+  }
+  else if (!(usbp->epc[ep]->in_state->txsize &
+            (usbp->epc[ep]->in_maxsize - 1))) {
+    /* Transmit zero sized packet in case the last one has maximum allowed
+       size. Otherwise the recipient may expect more data coming soon and
+       not return buffered data to app. See section 5.8.3 Bulk Transfer
+       Packet Size Constraints of the USB Specification document.*/
+    chSysUnlockFromIsr();
+
+    usbPrepareQueuedTransmit(usbp, ep, &sdup->oqueue, 0);
 
     chSysLockFromIsr();
-    usbStartTransmitI(usbp, USB_CDC_DATA_REQUEST_EP);
+    usbStartTransmitI(usbp, ep);
   }
 
   chSysUnlockFromIsr();
diff --git a/testhal/STM32F4xx/USB_CDC/main.c b/testhal/STM32F4xx/USB_CDC/main.c
index 027f92a81..34bdf55eb 100644
--- a/testhal/STM32F4xx/USB_CDC/main.c
+++ b/testhal/STM32F4xx/USB_CDC/main.c
@@ -324,16 +324,20 @@ static void usb_event(USBDriver *usbp, usbevent_t event) {
 }
 
 /*
+ * USB driver configuration.
+ */
+static const USBConfig usbcfg = {
+  usb_event,
+  get_descriptor,
+  sduRequestsHook,
+  NULL
+};
+
+/*
  * Serial over USB driver configuration.
  */
 static const SerialUSBConfig serusbcfg = {
-  &USBD1,
-  {
-    usb_event,
-    get_descriptor,
-    sduRequestsHook,
-    NULL
-  }
+  &USBD1
 };
 
 /*===========================================================================*/
@@ -480,12 +484,19 @@ int main(void) {
   chSysInit();
 
   /*
+   * Initializes a serial-over-USB CDC driver.
+   */
+  sduObjectInit(&SDU1);
+  sduStart(&SDU1, &serusbcfg);
+
+  /*
    * Activates the USB driver and then the USB bus pull-up on D+.
+   * Note, a delay is inserted in order to not have to disconnect the cable
+   * after a reset.
    */
   usbDisconnectBus(serusbcfg.usbp);
   chThdSleepMilliseconds(1000);
-  sduObjectInit(&SDU1);
-  sduStart(&SDU1, &serusbcfg);
+  usbStart(&USBD1, &usbcfg);
   usbConnectBus(serusbcfg.usbp);
 
   /*