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cameo • Jul 16, 2007

Embedded Board unstable??

Hi guys,

Any embedded-hardware experts out there to help me ??

I hav a board built for a personal media player application.
it consists:
A Mips Processor
NOR Flash
2 Samsung 64Mb RAM
Audio Decoder etc.

When i turn the board on,it starts playing the videos on an interfaced LCD Display.But it plays for some time and hangs.I need to again restart the system.
The same board with the same design was built last year and is in production now.But now when we assembled it again these probs occurs.So i am sure that the software is working,the circuit design is ok and the board designing is also through.Apart from these what could be the problem.

let me know,if want me to explain more.

xheavenlyx • Jul 16, 2007
You know I am no expert of embedded systems but am presently studying about Linux enabled embedded systems.

One thing I can think after knowing that you have checked everything is that there might be some problems with the power supply noise, or interfacing noise.

Also check how you are connecting your LCD. Since there is a RS232 port, make sure the timing of serial data transfer is correct (if you are using the port that is)

Another thing is to try to use the dev board for something else if possible and see how things go. A little more info of how its working can be helpful.
cameo • Jul 16, 2007
Here you go.
The basic block of the board:-

A mips 32-bit processor interfaced to TFT LCD display.
It also has got two external DDR SDRAM of 64Mb each connected.
Then it has two RS232 ports,one for interfacing with the PC to see the program execution(yamon) thru the hyper terminal.
It has a 256Mb,NOR flash where in the boot loader is stored.
The next it has is an audio decoder chip interface to the processor.
And there is an SD-card insertion where in the operating systems and other applications are stored.
At first i'll load the boot loader in the NOR flash and assemble it.Thats only done once.
When i turn on the board,the OS in the SD-card memory is loaded and starts playing teh videos,which are stored in the same SD-card.

And the problem starts now.It plays,plays and will hang at some point.May not be at the same spot..its random.Again i need to restart the system.
The OS is built in WINCE architecture,and it is 100% ok.It was already tested and proven sometime back with older boards.

This is the situation: apart from thsi board,there is a power supply board interfaced to this main board which supplies 1.2,1.8,3.3,5V.

overall: { board on - video plays - hangs }
xheavenlyx • Jul 17, 2007
my o my, this is one of the most difficult situations to debug!

We cant even see whats going on. But what about the debug? can u rewrite the video player module to save a log file every time your run the video module?? Can u insert extra module with the OS to run, like a debugger to log everything!!?

secondly, read this article on 13 reasons why not to use Win CE/XP embedded. This article can give you a clue on why there is a problem with what you are doing and might be helpful.


And there is an SD-card insertion where in the operating systems and other applications are stored.
since your OS is in a flash drive, why not try Embedded Linux? Even RTLinux for realtime functionality can be used. These are just suggestions, so dont flame over which is better 😀. I have never done any of this but am extensively planning on trying Embedded Linux Dev systems. Here are a few Links: (Linux on MIPS)
cameo • Jul 18, 2007

Going crazy!
yea,i have a debugger in this.As i said i can connect one of those RS232 ports to the hyperterminal and i see the yamon.I can view all the booting messages,debugging messages and error messages,if happens etc.It throws lot of exceptional error messages while hanging.If i put it exactly,exception error happens in device.exe,core.dll,filesys.exe,gwes.exe etc.But its hard to find out how these errors are related to the hardware and in which part.These errors can occur due to number of reasons.

Basically,i repeat,my software and the OS is perfect.There is not even a bug in it.
Something silly to do with the hardware,But which part? Simply clue-less.
RachaelP • Jul 19, 2007

A couple of things to try. First off, check your decoupling of the power rails is adequate as high speed CPU's and memory can be quite sensitive.

It sounds to me though like it might be a DDR issue. Have you extensively checked the signal quality and timings? The last DDR system I designed we used a high end oscilloscope to check the data eyes and also do complete parametric checking. Would it be possible to get an exhaustive DDR memory soak test program and leave it running to see what happens?

xheavenlyx • Jul 21, 2007
Try Rach's idea first, and if possible copy the logged messages while video is running till it hangs, thats it. If getting the log messages here is really out of the way then just try the logic analyzer, but you know, it can get extremely exhaustive! Since oscilloscope or logic analyzers work on bits and bites, Debugging from that information will know.

So if you can please paste the error logs from ALL modules till the system hangs, paste about 10~20 seconds of log catch if you know the timing 😀 And also try other forums, dont forget, if you find the solution share it with us. Good Luck!!

Bytheway, a hardware problem can be found out from the logs too, like incorrect memory address or an exception can occur because of a hardware fault, again, as Rach said,

check your decoupling of the power rails is adequate as high speed CPU's and memory can be quite sensitive.
There should be capacitors (0.01uf or 0.1uf) placed about every power supply rail since they are susceptible to high freq noise. Connect em accross every Vss to Gnd. Is it correct Rach?
cameo • Aug 25, 2007

Now i doubt the impedance constraints.
See,the system bus,ie between the processor and the RAM,are supposed to be taken care with all those impedance issues rite?,I mean i shudve instructed the manufacturer to take that into consideration.
But what worries me is,last time when i manufactured i didnt tell them anything,but this tiem with the same gerbers ,shud i be telling him?
And the last time the board worked fine.
But this time,it is not stable.The only difference now is,both those chips are lead free now.Will that can cause any impedance issues with the tracks and making the board unstable?

any clues?
xheavenlyx • Aug 26, 2007
You just asked this in the other thread😀 Keep track of em in subscriptions. my answer was:

This is a good Q.

Actually, its right those tracks are impedance sensitive. Usually, in digital systems, the IC itself would have taken care of it, but anyway, it would be good to place bypass caps (0.1uf SMD) in parallel with the ground. ground being a large surface area of exposed metal or something, you'd know what your ground looks like.

And if you are realy considering this a serious project then I would advise you to buy a simulation software which simuates EM noise, high freq noise and what not!! It will be immensely helpful.

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