This problem just started after 3 days of working on a project.

I am using Arduino IDE in Windows 10.

When I go to upload "Blink," everything works fine. I connect the USB (sometimes I have to change the port from COM6 to COM5) and upload and it blinks. All good. Well, one weird thing: sometimes I'll upload Blink when it's COM5 and then after the upload I'll notice that the Arduino has switched to COM6. So I have to go in and manually update the Port.

But after I switch to whichever Port has MKR1000 listed on it and go to upload my other more complicated program that uses WiFi and the Nokia 5110 LCD, it seems to throw the Arduino for a loop. All of a sudden it either won't upload properly or say port cannot be found and starts disconnecting from the port about 15 seconds after I connect it, and I'm not able to upload anything.

Anyone have any clues what might be going on? Thank you.

Adding some information about the connections from NOKIA 5110 (also using a breadboard in between):

RST: to pin 6 on MKR1000
CE: to pin 4 on MKR1000
DC: to pin 7 on MKR1000
Din: to pin 3 on MKR1000
Clk: to pin 5 on MKR1000
VCC:to VCC on MKR1000
BL: to VCC on MKR1000
GND: to GND on MKR1000


The MKR board connects to computer over native USB support of the MCU. The handling of the USB is done by Arduino core functions linked at build to your sketch.

A consequence of using the native USB port is, if your sketch has a problem, it influences the USB communication. In this case you can activate the bootloader to handle the USB port and the upload. It is done by double clicking the reset button on board.

This applies to other SAMD boards (Zero, M0) and to AVR boards with native USB port (Leonardo, Micro) too.

  • I've tried doing that and still run into the same problems. The error says: "Port name - COM6; Method name - openPort(); Exception type - Port not found."
    – garson
    Oct 24 '18 at 18:00
  • the reset changes USB port. set in IDE the first port that the board usually uses. if the upload doesn't start do the double reset again while the IDE attempts to upload. the bootloader waits after reset for upload almost 10 seconds
    – Juraj
    Oct 24 '18 at 18:11

Are you powering MKR1000 via USB? That only gives you about 1/2 amp of total current. I wonder if you're exceeding the available current of your power source. Add up the peak current requirements of your Arduino, (with WiFi active) the LCD, etc.

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