Hello,
When using the Arduino USB port (Mega1280 in my case), it may occasionally happen that the communication will be lost, and the port will become unavailable (Access denied).
With standard RS232 the board and port can be reset with the hardware DTR line, but this can not be done with the USB port.
I have tried to overcome the reset using additional RS232 (using two serial ports) by connecting the RTS or DTR to the board's reset, but such connection, even when open, disturbs some Arduino functions and can not be used, and in any case, this is not a practical solution.
Has anyone an idea on how such USB port / board reset can be activated remotely ?
(I access the computer that communicates with the board remotely, via network or internet).
Thanks
This may be true, but because it is software signal, when the port access is denied, it can not pass through.
With normal RS232, the DTR is hardwired, enabling reset even with the port inaccessible.
USB has only TX/RX and thus it is totally blocked when inaccessible.
The Arduino Mega uses MAX3421E for the USB.
The Arduino Mega 1280 board uses a FT232 chip. http://arduino.cc/en/Main/arduinoBoardMega
That chip doesn't need to be reset, and if that chip is working, so is the reset to the ATmega1280.
I don't know what problem could be. Can you explain it once more ?
Or do you use a bad usb hub, or cheap usb cables, that causes the voltage for the Arduino board to be too low and it stops working and only a reset helps ?
Thanks.
You are probably right about the type of USB bridge in use, but this does not help my problem:
The board is directly connected to a well-powered (old times!) desktop USB port via a short standard cable, but it happens occasionally that the access to the port is blocked.
(As we all know, this can happen at times with any computer, any USB device).
As I mentioned, in my case the problem is that the computer and board in question are remote (in another location), thus there is no way to physically intervene (a USB re-connection would do the work).
What I currently do to solve this is by rebooting the computer remotely, but this is a bad solution.
I need to find a way to make sure that in such case the system (board, port) will self-boot.
Is there a software way to make the board reset itself if it can not establish communication?
(I suspect no, as it uses an external USB bridge?)?
Thx
samtal:
(As we all know, this can happen at times with any computer, any USB device).
I'm sorry, but we all don't know that. I didn't. It never happened in my life and I have never heard of it before.
I have the same doubts as Grumpy_Mike.
Perhaps some severe grounding or electricity problem could cause this. Is the Arduino connected to something else ? and that something else is connected to ground ? Or the computer is powered without the mains-ground connected ?
Or perhaps you have dirty usb connectors, maybe some contact-spray will help. Or your operating system is crumbling down with bad usb drivers, or the harddisk is damaged.
Thanks for your replies.
I am knowledgeable electronics Eng. and as such I can not see any hardware issue here, (unless I overlooked something).
The USB voltage at the board input is fine, clean and stable.
The fact is that by unplugging and reconnecting the USB plug for a second I can get it to work again (This means reconnecting the power).
(This is also what happens by rebooting the computer. It powers off and on the USB 5V).
As I wrote, regardless of what really happen, I need an advice on how I can guaranty that in the case the usb is blocked there will still be a way to release such block remotely, or internally by the board's program.
(By the way, I wonder: Has it never happen to you guys that a usb device will fail until you disconnect-reconnect? am I the only one to experience such ?)
Hi,
I surely want to answer any question you ask and get any help I can.
I think I answered the hardware questions, except pressing the reset which is not easy: As I wrote, the board is on a remote location and I have to wait until I get the freeze, then coordinate a visit to the site, then either go (by car) to that location or ask someone (no one knowledgeable) open the board box (It is in a special clean room) and press rest. A long story, isn't it?
So, any idea on how this can be done remotely will be appreciated.
Seeing if it restarts when pressing the reset switch will tell you if the problem is with your arduino or your PC.
Only when you know where the problem is can you hope to get a soloution.
And no I have never had an Arduino USB freeze like this in over seven years of using Arduinos.