Hi,
I've 10 UNO's for use with pupils.
When I take another board on the same computer, the com-port will change.
Why?
Yesterday, I tried to upload, but it don't work. Hardware configuration - Arduino UNO (COM 3), Tools-Serial Port- COM 3. Drivers are right installed.
And today, after a cold restart, it works well.
What can be happened?
When I works with my pupil, it isn't handy. When I know why things happen, i better can understand this problems.
Gr.
Johan
Don't know the underlying reason, but Windows seems to assign (non physical) comports dynamically .
That causes the comports to be differently with different PC's.
Best you can do imho is - teach the children that this is reality -
Second best is to number the Arduinos and "hard assign" them to a certain PC, the PC will probably remember the comport of the Arduino ..
Don't know the underlying reason, but Windows seems to assign (non physical) comports dynamically .
That causes the comports to be differently with different PC's.
Yes, it's always been a mystery to me how comm port numbers get assigned in regards to arduino boards. Does a arduino board have anything in it's FTDI or 8u2 serial converter chip that makes in unique from any other otherwise identical arduino board?
Lefty
No, I think it goes something like this: (my assumptions, no proof or so.)
Traditionally the comports were 1 or 2 hardwired set of registers for physical serial ports in the bios. WIth the coming of HAL (Hardware abstraction layer) it is recommended not to use these bios directly anymore (locking/conflicts etc).
Instead Windows creates virtual comports that were mapped upon the real devices and offered access to them. Anything that wants to be a serial port can be one -- hardware serial ports of course, bluetooth devices, modemsm and of course USB devices including Arduino's.
I think that WIndows has some list of which comport maps on which device and if a Arduino is plugged in the first free spot in the list is used, or if it is a known device it will be reuse the known portnumber.
robtillaart:
No, I think it goes something like this: (my assumptions, no proof or so.)
Traditionally the comports were 1 or 2 hardwired set of registers for physical serial ports in the bios. WIth the coming of HAL (Hardware abstraction layer) it is recommended not to use these bios directly anymore (locking/conflicts etc).
Instead Windows creates virtual comports that were mapped upon the real devices and offered access to them. Anything that wants to be a serial port can be one -- hardware serial ports of course, bluetooth devices, modemsm and of course USB devices including Arduino's.
I think that WIndows has some list of which comport maps on which device and if a Arduino is plugged in the first free spot in the list is used, or if it is a known device it will be reuse the known portnumber.
First avalible doesn't seem to be the case for me. My PC has two hardware com 1 and 2 serial ports, so they always show up in the IDE list. But I have one arduino board that always seems to show up as a com 5 another as a com 6 (even if there is no com5 being used), so it's still somewhat a mystery to me. As I have several arduino boards, one hardware serial 328, one FTDI 328, one Seeduino mega, one arduino mega1280, and a bunch of USB serial cables it can get quite confusing at times which is which. Lucky I don't usually have a need to have more then one board plugged into the PC at a time.
Lefty
robtillaart:
Best you can do imho is - teach the children that this is reality -
Second best is to number the Arduinos and "hard assign" them to a certain PC, the PC will probably remember the comport of the Arduino ..
I could teach the children that this is reality.
But I couldn't teacht the computersystemmanager at school that this rights will be necessary to be changed by pupul in hardwareconfiguration... 
Thanks for further information...
Johan