# Leonardo Programming Problems **URL:** \ **Category:** Programming\ **Created:** [June 15, 2022, 7:25am UTC](https://forum.arduino.cc/t/leonardo-programming-problems/1002995 "2022-06-15T07:25:50Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![daniel0290](https://avatars.discourse-cdn.com/v4/letter/d/ebca7d/32.png) [@daniel0290](https://forum.arduino.cc/u/daniel0290)\ **Post date:** [June 15, 2022, 7:25am UTC](https://forum.arduino.cc/t/leonardo-programming-problems/1002995/1 "2022-06-15T07:25:50Z")
Hi, I have some problems programming my leonardo. With my UNO as ISP I burned a new bootloader and, for testing, a little blink-sketch. When connecting via USB I see the COM-Port. When start uploading a sketch with Arduino IDE the COM-Port disappears as the board is resetted, but never apperas again. The RX and TX LEDs are flickering parallel. ON and L are on. What could be the problem? ---
**Author:** ![sterretje](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/sterretje/32/391294_2.png) [@sterretje](https://forum.arduino.cc/u/sterretje)\ **Post date:** [June 15, 2022, 7:35am UTC](https://forum.arduino.cc/t/leonardo-programming-problems/1002995/2 "2022-06-15T07:35:20Z")
> [@daniel0290](#): > > When start uploading a sketch with Arduino IDE the COM-Port disappears as the board is resetted, That's expected behaviour. If you're using Windows (your use of the word _COM-port_ indicates that, you should see another COM-port appearing for a couple of seconds. > [@daniel0290](#): > > but never apperas again. Please explain; you should get the original COM-port back after the upload. > [@daniel0290](#): > > With my UNO as ISP I burned a new bootloader and, for testing, a little blink-sketch. Did you burn the blink-sketch with the Arduino-as-ISP or via USB. With the former, the bootloader will be wiped unless you burned the hex-file that also contains the bootloader. ---
**Author:** ![daniel0290](https://avatars.discourse-cdn.com/v4/letter/d/ebca7d/32.png) [@daniel0290](https://forum.arduino.cc/u/daniel0290)\ **Post date:** [June 15, 2022, 7:41am UTC](https://forum.arduino.cc/t/leonardo-programming-problems/1002995/3 "2022-06-15T07:41:40Z")
The COM-Port does not come back, so the upload does not really start. The blink-skrecth was uploaded with Arduino-as-ISP. I think when using Arduino IDE the hex-file should contain a bootloader?! ---
**Author:** ![sterretje](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/sterretje/32/391294_2.png) [@sterretje](https://forum.arduino.cc/u/sterretje)\ **Post date:** [June 15, 2022, 8:08am UTC](https://forum.arduino.cc/t/leonardo-programming-problems/1002995/4 "2022-06-15T08:08:47Z")
> [@daniel0290](#): > > I think when using Arduino IDE the hex-file should contain a bootloader?! Two files are generated, e.g. blink.ino.hex and blink.ino.with\_bootloader.hex. With normal uploads via USB, it is definitely the former, when uploading via a programmer I'm 95% sure it's also the former. I suggest that you burn the bootloader first with the Arduino-as-ISP. After that the behaviour of the Leonardo in Windows device manager should be as below (COM ports can be different). **Normal operation** ![image](https://europe1.discourse-cdn.com/arduino/original/4X/5/5/0/550155173fed9177268c0700d28e95d8a04f72c4.png) **After press/release reset button or when an upload starts** ![image](https://europe1.discourse-cdn.com/arduino/original/4X/2/e/5/2e585af61679aa7667c7e9b15368e9f54e61664a.png) Next you can upload blink via USB and the above behaviour should not change. After that you can upload again with Arduino-as-ISP and see what happens. ---
**Author:** ![daniel0290](https://avatars.discourse-cdn.com/v4/letter/d/ebca7d/32.png) [@daniel0290](https://forum.arduino.cc/u/daniel0290)\ **Post date:** [June 15, 2022, 8:40am UTC](https://forum.arduino.cc/t/leonardo-programming-problems/1002995/5 "2022-06-15T08:40:13Z")
You're right. After burning the bootloader and NOT uploading a sketch via Arduino-as-ISP i'm able to upload sketches via USB again. I don't know why i missed that. Thank you!! ---
**Author:** ![system](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/system/32/1140315_2.png) [@system](https://forum.arduino.cc/u/system)\ **Post date:** [December 12, 2022, 8:40am UTC](https://forum.arduino.cc/t/leonardo-programming-problems/1002995/6 "2022-12-12T08:40:36Z")
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