Unstable USB flash drive and programming connection

12 Dec 2011

Hello, I have been using the mbed for a couple months and observed the following problems with the USB flash drive and programming:

- The USB flash drive sometimes gets re-detected by the laptop (two laptops so far, vaio and lenovo) without any power reset. This happens both on windows and linux. This occurs more often when there are other high current electronics around, but also when nothing is around.

- I have 'broken' three mbeds, i.e. at some point I could no longer put any files into the flash drive. In the flash drive, I could see some files with long invalid names (symbols) and when trying to write on it, there is an I/O error. This has happened with three different laptops running both windows and linux. After some tests, I observed that (so far) this happened only when the mbed is being flashed or when the usb is unplugged/plugged while sharing a ground with a power supply that is on. This has happened with two different power supplies (one 12V and one 24V). Now I'm very careful to turn off the power supply before flashing the mbed or unplugging/plugging usb and so far, this seems to get rid of this problem.

Has anyone encountered any or both of these problems? Any input would be greatly appreciated, as the mbed has enabled us to have super fast development and I'd really like to continue using it.

Many thanks in advance!

12 Dec 2011

mbed flash being re-detected may be the result of a power dip in the usb bus that is caused by another device on the bus or by some electronics that you drive from Vu. The USB bus can only provide some 100 mA. When you exceed that max current the PC protection circuitry may shut down the usb power, resulting in an mbed interface shutdown or reset.

Another reason for this effect may be a spurious reset of the mbed. Perhaps your nReset pin is floating and picks up some noise. I have noticed that sometimes just having your finger close to the reset switch will result in a reboot...

mbed flash drives that dont respond have been reported before. Some tricks to bring mbed back to life are here http://mbed.org/forum/mbed/topic/399/ and here http://mbed.org/cookbook/deadmbed

14 Dec 2011

Thank you very much for your input! It is very likely that I'm drawing too much current from the usb bus. I'll also try the described tricks to bring the broken mbeds back to life.

18 Aug 2012

My mbed seemed unreliable, but improved when I tried a shorter USB cable. I now also touch the connector case (ground) before I press the reset switch. Cheers, W

18 Aug 2012

Someone at mbed posted a test and cables can make a difference especially on lappys (they are shipping better cables with newer mbeds) I haven't had trouble with any cable , but if i plug it into my powered hub and have my webcam in the same hub Mbed goes crazy and resets only the webcam causes this effect so far for me

03 Jul 2014

I have the same problem as Lijin, I've already broken one MBED and one NUCLEO. Actually I tried almost everything in order to download the code in my Nucleo but at the end the only result I get is a fail.txt with inside the text : "RESERVED BITS".... At first, the board disconnected and reconnected but I don't have this problem anymore. I tried to flash its frimware, to external power it, to follow the deadMbed advices, but without proper results.

Did someone manage to find a solution to download files in these "broken" boards or to repair them ?

04 Jul 2014

Hello, did you try to connect with the STLink utility ?
STLink utility on ST web page
With this tool, you should be able to upgrade the ST-Link firmware (in the STM32F103, the debugger device) and read/write code or erase the target device memory. This should let you check if it's an hardware failure and on which chip.

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