STM32 DFU: more improvements

examples/stm_dfu/src/main/java/net/codecrete/usb/dfu/DFU.java

@@ -64,6 +64,7 @@ public static void main(String[] args) {
             System.out.println("Firmware successfully downloaded and verified");
 
             device.startApplication();
+            device.waitForDisconnect();
             System.out.println("DFU mode ended and firmware started");
 
             device.close();

examples/stm_dfu/src/main/java/net/codecrete/usb/dfu/DFUDevice.java

@@ -133,6 +133,27 @@ public void close() {
         usbDevice.close();
     }
 
+    /**
+     * Waits until the device disconnects.
+     * <p>
+     * Disconnection is a side effect of leaving DFU mode.
+     * </p>
+     * <p>
+     * If the device does not disconnect after 5 seconds,
+     * an exception will be thrown.
+     * </p>
+     */
+    public void waitForDisconnect() {
+        var waitingTime = 5000;
+        while (waitingTime > 0 && usbDevice.isConnected()) {
+            sleep(100);
+            waitingTime -= 100;
+        }
+
+        if (usbDevice.isConnected())
+            throw new DFUException("Device did not restart (try disconnecting and reconnecting it)");
+    }
+
     /**
      * Clears an error status.
      */
@@ -170,7 +191,7 @@ public DFUStatus getStatus() {
     public byte[] read(int address, int length) {
         expectState(DeviceState.DFU_IDLE, DeviceState.DFU_DNLOAD_IDLE);
         setAddress(address);
-        exitDownloadMode();
+        exitMode();
         expectState(DeviceState.DFU_IDLE, DeviceState.DFU_UPLOAD_IDLE);
 
         var result = new byte[length];
@@ -187,20 +208,7 @@ public byte[] read(int address, int length) {
             blockNum += 1;
         }
 
-        // request zero length chunk to exit out of upload mode
-        var transfer = createDfuControlTransfer(DFURequest.UPLOAD, blockNum);
-        usbDevice.controlTransferIn(transfer, 0);
-
-        DFUStatus status;
-        try {
-            status = getStatus();
-        } catch (DFUException e) {
-            // Device might respond with an empty response; try again
-            status = getStatus();
-        }
-
-        if (status.state() != DeviceState.DFU_IDLE)
-            throw new DFUException("Unexpected state after exiting from upload mode");
+        exitMode();
 
         return result;
     }
@@ -247,7 +255,7 @@ public void download(byte[] firmware) {
             transaction += 1;
         }
 
-        exitDownloadMode();
+        exitMode();
     }
 
     /**
@@ -327,7 +335,7 @@ private Page findPage(int address) {
         return Segment.findPage(segments, address);
     }
 
-    private void exitDownloadMode() {
+    private void exitMode() {
         abort();
 
         var status = getStatus();
@@ -340,6 +348,8 @@ private void exitDownloadMode() {
     public void startApplication() {
         expectState(DeviceState.DFU_IDLE, DeviceState.DFU_DNLOAD_IDLE);
 
+        // By sending a zero-length download packet and querying the status,
+        // the device will leave DFU mode and restart.
         var transfer = createDfuControlTransfer(DFURequest.DOWNLOAD, 0);
         usbDevice.controlTransferOut(transfer, null);
 

examples/stm_dfu/src/main/java/net/codecrete/usb/dfu/DFURequest.java

@@ -10,15 +10,47 @@
 /**
  * DFU request.
  * <p>
- * See USB Device Class Specification for Device Firmware Upgrade, version 1.1.
+ * See ST Microelectronics, application note AN3156.
  * </p>
  */
 public enum DFURequest {
+    /**
+     * Requests the device to leave DFU mode and enter the application.
+     * <p>
+     * The Detach request is not meaningful in the case of the bootloader. The bootloader starts
+     * with a system reset depending on the boot mode configuration settings, which means that
+     * no other application is running at that time.
+     * </p>
+     */
     DETACH,
+    /**
+     * Requests data transfer from Host to the device in order to load them
+     * into device internal flash memory. Includes also erase commands.
+     */
     DOWNLOAD,
+    /**
+     * Requests data transfer from device to Host in order to load content
+     * of device internal flash memory into a Host file.
+     */
     UPLOAD,
+    /**
+     * Requests device to send status report to the Host (including status
+     * resulting from the last request execution and the state the device
+     * enters immediately after this request).
+     */
     GET_STATUS,
+    /**
+     * Requests device to clear error status and move to next step.
+     */
     CLEAR_STATUS,
+    /**
+     * Requests the device to send only the state it enters immediately
+     * after this request.
+     */
     GET_STATE,
+    /**
+     * Requests device to exit the current state/operation and enter idle
+     * state immediately
+     */
     ABORT
 }