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PICList Thread
'[PIC] RealICE oddities'
2010\10\05@120927 by Lorenzo Luengo

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 Yesterday, I was happily working with my RealICE and a PIC18F4550, and
suddenly things became weird.

When trying to program the PIC it said that device type did not match,
the reported one was 0x0000000 instead of 0x0001200 (maybe they did not
have that much zeros).

I tried power cycling the PIC, with no success.

Then i tried another (new) chip of the same PIC, but the error persisted.

Having a look at the signals PGD an PGC with a scope, there was
something wrong. The signals looked like if the power supply of RealICE
was unable to keep VDD constant (just like a discharging capacitor, down
to 1V approx).

This made me sigh... Did I trash my RealICE?

Then i tried a loopback test, but it ran smoothly.

Finally after removing the driver card, and USB cable and reconnecting,
the RealICE worked fine again. I could not find a reasonable explanation.

Does anyone have an idea on what could have happened?

--
Lorenzo Luengo Contreras
Ingeniero Civil Electrónico
Laboratorio MIDGEO (LF-106)
Facultad de Ciencias Físicas y Matemáticas
Universidad de Concepción
Concepción - Chile
+56-41-2207400
http://midgeo.udec.cl

2010\10\05@124419 by Oli Glaser

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--------------------------------------------------
From: "Lorenzo Luengo" <spam_OUTlluengoTakeThisOuTspamdgeo.udec.cl>
Sent: Tuesday, October 05, 2010 5:09 PM
To: "Microcontroller discussion list - Public." <.....piclistKILLspamspam@spam@mit.edu>
Subject: [PIC] RealICE oddities

{Quote hidden}

Do you have to plug a test board in to do the loopback test with the RealICE?
I have never used one..
My guess is you may have had a dodgy connection on your programming header, and unplugging/plugging it back in sorted it out - without more consideration/information though I would definitely not bet on this being correct...

2010\10\05@143121 by Lorenzo Luengo

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 El 05-10-2010 12:43, Oli Glaser escribió:
>
> Do you have to plug a test board in to do the loopback test with the
> RealICE?
Yes, it came with RealICE
> I have never used one..
> My guess is you may have had a dodgy connection on your programming header,
> and unplugging/plugging it back in sorted it out - without more
> consideration/information though I would definitely not bet on this being
> correct...
Now I have scope-shots of what's happening to PGC. It happens when trying to program, after device identification.

Good one: During device identification

http://imagebin.ca/view/EvuM_A.html

Bad one: When trying to program

http://imagebin.ca/view/dW3oAmVv.html

I think that I'll need to make a new cable for the programming header, this problem is happenning only sometimes, maybe a protoboard problem?
--
Lorenzo Luengo Contreras
Ingeniero Civil Electrónico
Laboratorio MIDGEO (LF-106)
Facultad de Ciencias Físicas y Matemáticas
Universidad de Concepción
Concepción - Chile
+56-41-2207400
http://midgeo.udec.cl

2010\10\05@224240 by John Chung

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>From the bad picture, I would say it is the protoboard itself. A bad cable usually distorts the entire clock not the first cycle itself. Try generating a signal through that cable and use the scope WHILE bending the wires at both ends.

John


{Quote hidden}

> -

2010\10\06@023246 by Lorenzo Luengo C.

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 El 05/10/2010 22:42, John Chung escribió:
> > From the bad picture, I would say it is the protoboard itself. A bad cable usually distorts the entire clock not the first cycle itself. Try generating a signal through that cable and use the scope WHILE bending the wires at both ends.
>

Even more odd... after those programming failures, the RealICE did not detect when i disconnected the target device and i could do a fake "program" cycle with it (no cable connected) and the clock looked the same. So i think that it's something inside my RealICE.

Anyway, thanks for the tip John.

{Quote hidden}

>> --

2010\10\06@024406 by John Chung

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Do keep us posted on issue.
Regards,
John



--- On Wed, 10/6/10, Lorenzo Luengo C. <lluengospamKILLspamdgeo.udec.cl> wrote:

{Quote hidden}

2010\10\06@043105 by alan.b.pearce

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> Even more odd... after those programming failures, the RealICE did not
> detect when i disconnected the target device and i could do a fake
> "program" cycle with it (no cable connected) and the clock looked the
> same. So i think that it's something inside my RealICE.
>
> Anyway, thanks for the tip John.

I would be suspicious of a dry joint on the connector pins.
-- Scanned by iCritical.

2010\10\06@044621 by Oli Glaser

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--------------------------------------------------
From: <alan.b.pearcespamspam_OUTstfc.ac.uk>
Sent: Wednesday, October 06, 2010 9:21 AM
To: <@spam@piclistKILLspamspammit.edu>
Subject: RE: [PIC] RealICE oddities

>> Even more odd... after those programming failures, the RealICE did not
>> detect when i disconnected the target device and i could do a fake
>> "program" cycle with it (no cable connected) and the clock looked the
>> same. So i think that it's something inside my RealICE.
>>
>> Anyway, thanks for the tip John.
>
> I would be suspicious of a dry joint on the connector pins.

I agree - maybe try wiggling the cable while it's plugged in to the RealICE socket and watch the scope. It could be the actual cable or the the RealICE socket itself.

2010\10\08@150416 by Lorenzo Luengo

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 D'oh!!!

All this trouble was caused because of a too little pullup resistor between VPP/MCLR pin and VDD. It was a 120 ohm only, I thought it was 1k or greater. I swapped it with a 10k resistor and everything went back to normal, after reconnecting my RealICE to USB port. The weird thing is that the "bad" waveform was reproduced even with the cable physically disconnected from the emulator.

Now things are working smoothly. Hope it lasts.

Thanks everyone for the patience.

El 06-10-2010 2:44, John Chung escribió:
{Quote hidden}

-- Lorenzo Luengo Contreras
Ingeniero Civil Electrónico
Laboratorio MIDGEO (LF-106)
Facultad de Ciencias Físicas y Matemáticas
Universidad de Concepción
Concepción - Chile
+56-41-2207400
http://midgeo.udec.cl

2010\10\09@035304 by John Chung

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good to know it is solved. BTW the waveform does help quite a bit for debugging purposes. At least I know what to expect when there is NO load.


Regards,
John





--- On Fri, 10/8/10, Lorenzo Luengo <TakeThisOuTlluengoEraseMEspamspam_OUTdgeo.udec.cl> wrote:

{Quote hidden}

> -

2010\10\10@032752 by Lorenzo Luengo C.

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 El 09/10/2010 3:53, John Chung escribió:
> good to know it is solved. BTW the waveform does help quite a bit for debugging purposes. At least I know what to expect when there is NO load.
>

John, i'd just like to notice that waveform was with no load but *after* a failed programming attempt. I haven't tried to see the clock signal on normal programming conditions, but i suspect it's a normal square wave, sweeping from zero to vdd.
{Quote hidden}

-- Lorenzo Luengo Contreras
Ingeniero Civil Electrónico
Laboratorio MIDGEO (LF-106)
Facultad de Ciencias Físicas y Matemáticas
Universidad de Concepción
Concepción - Chile
+56-41-2207400
http://midgeo.udec.cl

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