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Arduino COM3, COM4 HELP Answered

Hey, I recently bought an Adafruit Motor Shield 1.1, but i'm having problems programming it. Everytime I try to upload a program, it tells me it cant find the COM4 port, only the COM3, which doesnt finish uploading. Also, COM4 works fine when I detach the motor shield from the Arduino UNO and play with LED's. I'm only a beginner, so I have no idea what to do.



5 years ago

I fixed this situation quite easily, so if anyone is having the same problems, hears a solution. So plug in your Arduino, go into device manager>ports>and see what COM port your arduino needs. Noting this down, go back to the Arduino IDE and select which COM port you need(tools>serial port, and select which COM port.).
Also, I recommend that your should always plug in your USB cable into the same port on your computer.


5 years ago

Did you try uploading the program before attaching the shield? If the shield is using the RX/TX pins then it may be messing up the connection.

Yes, I uploaded it to the UNO(on COM4), then I attached the motor shield, but nothing happened. Is it a good idea to desolder the pins on pin0,1 so that nothing is connected?

I wouldn't. I would go over to the Arduino Forum where you can post your code and get help. I do mostly blinky lights, haven't done motors yet.

Just to cover your bases, check your solder job on the headers for pins 0 and 1. If you managed to short those to each other, or to something else on the shield, that could cause wacky COM-port behavior since they're the serial pins for the Arduino.

I think my soldering job is good. Its not connected together or anything.

I, personally, cannot help, but have you tried asking on the Adafruit forums?  Or checking their tutorials?

Forum link.
Tutorial link.