[Microbit-Python] Testing Point Documentation

Tue Apr 5 04:38:47 EDT 2016

Hi Giles,

I've been in touch with Philip and he'll be sending me a replacement shortly (thanks Philip!). Below is a description of my usage of my micro:bit (taken from my email to Philip).

Apart from two or three times where it was powered from the official 2x AAA battery charger, I've exclusively powered it over USB from the USB port on my laptop. (Sony VAIO VGN-C2S running Debian 7 GNU / Linux).  When the issue developed, I was powering it from my laptop and hadn't powered it off batteries for at least four days. It has never been powered off a mains phone charger.

When using it though USB I have always used the supplied USB cable. I am not aware of any ESD events, and when not in use I stored the micro:bit in the original anti-static bag. I'm not quite sure what you mean by 'grounded', the device was plugged into the laptop through USB but the laptop was not connected to mains. (If you mean something else, please let me know).

The fault occurred whilst I was testing the serial output of the micro:bit. It was running a Python program to output some text and wait 1 second whenever the 'A' button was pressed. I was using the 'screen' utility to view the output. ('screen /dev/ttyACM0 115200'). Mid-way through the testing, the screen session exited, and I noticed that the power LED on the micro:bit had gone off. About ten seconds later I realised that the micro:bit was getting hot, and so I unplugged it from the computer.

As far as I can think of there has been nothing else during the use of the device that could have caused this. I was the first person to use the device (the teacher used one of the other three devices that was sent). As far as use is concerned, I have flashed it with various different .hex files, but have not used the I/O ports at all so it has not been connected to any device which could have caused the problem.

Giles, which chip on your micro:bit got hot? (On mine it was the USB serial chip), and how hot did they get - particularly the one that kept working? Mine got too hot to touch after about 20 seconds, and after about 30 the other side of the board got very hot as well.

Andrew

On 5 Apr 2016, at 09:20, Giles Booth <giles.booth at gmail.com> wrote:

> Hi Andrew - very interested to hear about this as I had the same experience with 3 out of 4 of my initial teacher microbits. One got very hot and died, another got very hot but remained working, a third runs much warmer than the 4th unit. The last unit that died was a replacement and had only been used in a classroom and never had anything attached to its GPIO pins. 
> 
> Phil Meitiner and BBC have been very helpful, sending me 5 more microbits to test - all ok but not tested with actual children, which was when my initial teacher units started to malfunction. 
> 
> Andrew, did you use the GPIO pins at all with yours or just USB?
> 
> many thanks
> 
> Giles
> 
> On 4 April 2016 at 15:46, Andrew Ferguson 500 <andrewferguson500 at gmail.com> wrote:
> Hi Nicholas,
> 
> Ah, my micro:bit does not have a tick, so that's probably the problem.
> 
> Is there any more info anywhere about this overheating problem? (how it occurs, what can be done to avoid it, etc...).
> 
> On 4 Apr 2016, at 15:22, "Nicholas H.Tollervey" <ntoll at ntoll.org> wrote:
> 
> > If it has a tick mark on the front, top left corner (where the "hair"
> > is), then I believe it's been checked for the overheating problem and
> > passed. No tick = likely to be an earlier pre-solution version of the board.
> >
> > N.
> >
> > On 04/04/16 15:24, Andrew Ferguson 500 wrote:
> >> Thanks, it does get quite hot if left on for more than ~30 seconds.
> >> (After about 10 it is too hot to touch, after 20 it is very warm on
> >> the other side of the board. I haven't left it on for more than about
> >> 2-3 minutes).
> >>
> >> This was one of the teacher devices so it could be a slightly earlier
> >> version than the final student devices.
> >>
> >> On 4 Apr 2016, at 15:13, Damien George <damien.p.george at gmail.com>
> >> wrote:
> >>
> >>> There was a problem with some of the microbit's having their USB
> >>> chip get "hot" but I thought it was resolved.  I'll ask Jonny about
> >>> it.
> >>>
> >>> On Mon, Apr 4, 2016 at 2:44 PM, Andrew Ferguson 500
> >>> <andrewferguson500 at gmail.com> wrote:
> >>>> No, the computer does not recognise the micro:bit. If I power the
> >>>> micro:bit from the 2x AAA batteries nothing happens at all. (No
> >>>> light, no chips getting hot).
> >>>>
> >>>> Hopefully more stuff will be released as Free Software / open
> >>>> source soon (especially the DAL and the iOS and Android apps).
> >>>>
> >>>>
> >>>> On 4 Apr 2016, at 14:35, "Carlos P.A." <carlos.p.a.87 at gmail.com>
> >>>> wrote:
> >>>>
> >>>> I haven't seen any schematics out yet, that seems to be part of
> >>>> the documentation that still needs to be open sourced. From the
> >>>> top of my head I vaguely remember the test points at the back
> >>>> probably connected to the microcontroller in charge of the USB
> >>>> communication (and, I assume, the battery controller), so they
> >>>> might be a programming interface more than actual test points.
> >>>>
> >>>> Does you computer recognise the microbit at all?
> >>>>
> >>>> On 4 April 2016 at 14:27, Andrew Ferguson 500
> >>>> <andrewferguson500 at gmail.com> wrote:
> >>>>>
> >>>>> Hi,
> >>>>>
> >>>>> I managed to persuade my teacher to let me borrow a teacher
> >>>>> Micro:bit over the Easter holidays (I'm in Scotland so the
> >>>>> student devices haven't arrived yet), but unfortunately I seem
> >>>>> to have broken it. (I was just using 'screen' to test serial
> >>>>> communication, one minute it worked and the next the screen
> >>>>> session had closed, the micro:bit status light was off and the
> >>>>> USB chip on the micro:bit got very hot).
> >>>>>
> >>>>> I suspect it's probably irreversibly broken, but I noticed that
> >>>>> on the back of the micro:bit there are several testing points
> >>>>> that may provide some insight as to what went wrong if probed
> >>>>> with a multimeter. Does anyone know if there are any docs
> >>>>> relating to which testing point links to what?
> >>>>>
> >>>>> Thanks, Andrew
> >>>>>
> >>>>>
> >>>>> _______________________________________________ Microbit
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> >>>>
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> 
> -- 
> Giles Booth
> www.suppertime.co.uk/blogmywiki
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