Communication problem Arduino Mega 2560 - PC

[Bernhard M. (Firma: lala) (bernhard86)]

Hello,

we have a project where we use an Arduino Mega 2560 for datalogging. The 
arduino sends
periodically (2s cycle) a string containing different sensor values. On 
the PC (Windows 7 and Windows XP) we use logview
for visualization (www.logview.info/) which works well for our purposes.
The stringformat
for logview is described here: 
http://www.logview.info/cms/d_formatbeschreibung.phtml

Our problem is that logview hangs up from time to time. The serial 
logging stops and logview can't
open the COM-Port anymore. The only solution is to unplug and reconnect 
the USB-cable. Unfortunately, this
isn't an acceptable solution for us.

What we have tried so far:

- We removed all sensors/actors from the Arduino Mega 2560 and sent only 
dummy strings over USB -> logview still hangs up
- We reduced the baudrate --> it seems, that the device doesn't hangs up 
so often (but still hangs up)
- We used shorter USB-cables --> it seems, that the device doesn't hangs 
up so often (but still hangs up)
- We used on the PC a simple PC-program writing serial data to a file 
(instead of logview) --> also hangs up
- We connected an additional arduino USART/USB converter to the second 
USART from the Arduino and sent the same strings over both UARTS. On PC 
we watched both ports with logview and putty -> both hanged up
- We tested this also with different PC's.


You have any idea? We think that it could be

- problem with ground
- problem with windows

Best regards

[innerand i. (innerand)]

Is the Arduino powered over USB? If, try an USB-Hub with own power 
source.
Maybe some voltage drop causes an reset?

Another point could be the Auto-Reset from the Arduino-Board. Try to put 
an 120 Ohm Resistor (min 110, max 124 Ohm) between Reset and 5V or cut 
the wire "Reset EN" on the board. (see: 
http://playground.arduino.cc/Main/DisablingAutoResetOnSerialConnection )

When you say the device hangs up, do you mean that the arduino stops 
working  or is it just the communication that breaks?

[bernhard86 (Gast)]

The arduino itself does not hang up: In the test where we sent the 
output string over two UARTS they boths hang up independently (not at 
the same time). So we can be sure that the arduino continues to send the 
strings after hangup.

The only thing is that the COM-port on the PC is lost and our 
visualization tool stops operating. When we unplug and reconnect the 
USB-cable the visualization works again (without reseting the arduino).

Best regards

[innerand i. (innerand)]

bernhard86 schrieb:

> The only thing is that the COM-port on the PC is lost and our
> visualization tool stops operating. When we unplug and reconnect the
> USB-cable the visualization works again (without reseting the arduino).

Usually (that means you didn't do anything to avoid this) the arduino is 
reseted every time a serial connection (over the usb-plug) is 
established.

Can you confirm, that the arduino is not resetting when the connection 
gets lost?

[bernhard86 (Gast)]

Ok, when rethinking the whole test scenario I am not able to confirm 
that the arduino is not resetting. It may also be possible that the 
arduino restarts, but this isn't a problem since the arduino starts 
logging again immediately. But we will try to find out ...

We will also try to cut
the wire "Reset EN" and to run a long time test again - but this isn't a 
good solution since the arduino isn't programmable any more (via remote 
access).

best regards

[innerand i. (innerand)]

If you need auto reset don't cut it, use the resistor.

Just found out that there is a second µC on the MEGA 2560 managing the 
usb connection. In its firmware there were some bugfixes affecting 
buffering.
Eventually check if the firmware on your Arduino is the newest one.

[PittyJ (Gast)]

I also have sometimes Problems with COM-Driver for Arduino and Windows. 
I think, it is a Windows-related problem.
With Linux I talk directly over libusb, without a Com or TTY driver. And 
there are no problems over several monthes.

[bernhard86 (Gast)]

We have checked the firmware on our Arduino: it is the newest one.

At the moment we try the same test with a debian-linux pc.

Best regards