Issue 1 - this is normal. The LED is flashed by the bootloader code just after reset while it is waiting to see if there is code to download or if the code in the Arduino needs to be run.
No idea about the other issue, is your USB lead OK?
The LED marked "L" is connected to pin 13.
Blinking during bootup is normal behaviour.
It can be used in a sketch as indicator LED.
The "Blink" sketch uses it.
Try loading that into your UNO.
You can find it in the IDE in > File > Examples > basics.
Try playing with the delay times (reload the sketch every time).
Not sure why your computer drops the COM port.
Try another USB cable. Some printers use the same one.
Or try another USB port on your computer.
Leo..
Hi,
I find it unusual that COM 3 is being used for Arduino, I have WIN7 and all my arduino boards do not have COM port allocations below COM10.
In fact when working with industrial apps if COM3 is selected I get unstable results at times and I reassign the COM port in the relevant driver.
I'm not sure but I think COM3 is used for internal connections, such as virtual modems, fax or ISP, so I never let an app use any COM under 10.
Plug the Arduino in, and go to "Device Manager" > Ports > Arduino port properties.
Port settings tab > Advanced button.
Dropdown box.
Look at what ports are in use.
It might have several old/unused assignments.
Windows won't let go of old settings.
Just use a lower one, even if it's listed as "in use".
A cold start (reboot) with the Arduino plugged in might also force it on a lower port.
Leo..
Tom George:
Hi,
I find it unusual that COM 3 is being used for Arduino, I have WIN7 and all my arduino boards do not have COM port allocations below COM10.
In fact when working with industrial apps if COM3 is selected I get unstable results at times and I reassign the COM port in the relevant driver.
I'm not sure but I think COM3 is used for internal connections, such as virtual modems, fax or ISP, so I never let an app use any COM under 10.
Tom....
The UNO I just plugged in uses COM5. All my UNOs and Mega use ports numbered below 10. Win10, and previously WinXP and Win7.
As Wawa says, Windows will think all lower ports are in use, even by devices that aren't connected at the moment.
I haven't tried it with Win10 yet, but to get rid of unused but allocated serial ports in WinXP SP3 and Win7. (Also works with Win7 64-bit):-
The trick is to open the Command Prompt as administrator and start the Device Manager from the same command prompt.
Right-click “Command Prompt” in Accessories and choose “Run as Administrator”
Enter “set devmgr_show_nonpresent_devices=1?" – without the quotes obviously
Enter “start devmgmt.msc”
In the box that opens, select “Show hidden devices” in the ‘view’ menu.
Now if you expand the section on COM ports, all the COM ports that have ever
been created will be displayed, the non present ones being in grey. You can
uninstall away anything that you don’t want (right click, select uninstall).
Edit: As far as I know, too, COM3 isn't reserved for any special purposes. On three different computers, I've had a CP2101 USB to TTL module connected to that port, along with an APC220 RF module, to receive alarms from my workshop alarm system.
Hi,
Been there, thats how I change COM numbers, but arduino is the ONLY COM port on my home laptop.
My works comp has other COMs open for apps that are used to talk to UPS's PLC's and VSDs, they all reside in the background.
TomGeorge:
Hi,
Been there, thats how I change COM numbers, but arduino is the ONLY COM port on my home laptop.
My works comp has other COMs open for apps that are used to talk to UPS's PLC's and VSDs, they all reside in the background.
Tom...
Right. That's only specific to your work computer(s) though. It's not the case with COM3 in general.
(I just edited my last post and added a little.)
Edit:
Hi,
Been there, thats how I change COM numbers, but arduino is the ONLY COM port on my home laptop.
Hmmm, it surprises me that it won't allocate port numbers below 10, if that's your only COM port.
I think the moment Window$ detects a different serial/USB chip, it assigns a next COM port number.
I use an Uno, Nano and Mega.
The Mega is now COM5 (was COM3, but has been >COM10).
Just move to a lower number manually if it's getting out of hand.
Leo..
Wawa:
I think the moment Window$ detects a different serial/USB chip, it assigns a next COM port number.
I use an Uno, Nano and Mega.
The Mega is now COM5 (was COM3, but has been >COM10).
Just move to a lower number manually if it's getting out of hand.
Leo..
Every now and then I follow the procedure described above, and 'clean house'.
