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Christophe
Joined: 10 May 2005 Posts: 323 Location: Belgium
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rberek
Joined: 10 Jan 2005 Posts: 207 Location: Ottawa, Canada
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Posted: Thu Jun 15, 2006 5:07 am |
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Your pull up should be 47K on the reset if you are programming with the ICD.
I this the small resisitor let the reset pin sink way too much current. |
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Christophe
Joined: 10 May 2005 Posts: 323 Location: Belgium
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Posted: Thu Jun 15, 2006 5:14 am |
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How is that?
Don't you see the 390K ohms in series with the MCLR and the button. |
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Ttelmah Guest
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Posted: Thu Jun 15, 2006 5:24 am |
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First comment. You show connections being bought out to a header, as though you are going to use LVP ICSP. If so, the PGM line, should have a resistor to GND, otherwise during bootup, when the pin is programmed as an input, the line can float enough to trigger programming.
Second comment, there are a lot of lines going 'off circuit' (SCAN, Dn etc.). What do these connect to, how are these protected?.
I'd seriously consider having a zener across the piezo element, and a resistor to limit any back emf into the PIC. Remember a piezo element, can both convert voltage to sound, and also operate the other way. This is how piezo lighters etc., work. If an impact takes place on the piezo module, it is very possible that this could have damaged the pin to which it is connected, or the rest of the PIC...
Best Wishes |
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Christophe
Joined: 10 May 2005 Posts: 323 Location: Belgium
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Posted: Thu Jun 15, 2006 5:29 am |
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The problem is round the MCLR line. When I connected my programmer, my pic dies!
the data and scan lines are protected at the place where ESD sparks can enter the circuit (not shown).
Don't think the buzzer killed the PIC. The cause is around MCLR line, I don't understand how.
Pin RB3 is used for debugging using the CCS C compiler/programmer |
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rberek
Joined: 10 Jan 2005 Posts: 207 Location: Ottawa, Canada
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Posted: Thu Jun 15, 2006 5:40 am |
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I apologize. I went only by your verbal description. |
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asmallri
Joined: 12 Aug 2004 Posts: 1634 Location: Perth, Australia
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Re: Why did my PIC die? |
Posted: Thu Jun 15, 2006 5:54 am |
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You have not used standard reset circuitry.
You should not have the 2.2uF capacitor on the reset line in this configuration. It will result in the 12 volt remaining applied to the reset pic after you have programmed the chip which in turn can result in the PIC being erased or erroneously programmed.
390K is too high a value, especially if there is any leakage current with the capacitor.
The Piezo could damage the port pin (not likely).
If R4/R5 is meant to allow you to measure the battery voltage then this is way outside the supported input impedance to the A/D - it should be less than 2.5K - you should consider putting an opamp configured as a voltage follower between the divider and the PIC. If you stay with just a voltage divider (can't see how you can) then you should also add a diode (preferably schottky) from the resistor junction to the PIC VCC rail.
The same goes for Vadap on AN1. _________________ Regards, Andrew
http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!! |
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Christophe
Joined: 10 May 2005 Posts: 323 Location: Belgium
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Posted: Thu Jun 15, 2006 6:02 am |
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Thanks for input, I understand your remarks, but I still don't understand why the PIC died. |
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Humberto
Joined: 08 Sep 2003 Posts: 1215 Location: Buenos Aires, La Reina del Plata
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Posted: Thu Jun 15, 2006 6:09 am |
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rberek you are right.
Quote: |
Your pull up should be 47K on the reset if you are programming with the ICD.
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Christophe, first of all you must wire the ICD according to CCS spec, then if it doesnīt work, you should search another causes.
http://www.ccsinfo.com/faq.php?page=icd_connection
Humberto |
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Christophe
Joined: 10 May 2005 Posts: 323 Location: Belgium
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Posted: Thu Jun 15, 2006 6:15 am |
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Humberto, for SURE it works following the CCS ICD specs.
I want to know why it does not work how I wired it.
My PIC died because of something and I want to know why.
edit: That Pic still programs but on verify it reads all 0000h on all adresses. So it's dead. |
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Ttelmah Guest
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Posted: Thu Jun 15, 2006 6:33 am |
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I'd say Tvhhr.
The data sheet requires the voltage on Mclr, to rise from Vdd to Vihh in less than 1uSec. I presume that during the transition, the charge pump does not properly start, and may well overheat. Having a capacitor directly on the Mclr pin, will prevent this from happening.
Best Wishes |
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Humberto
Joined: 08 Sep 2003 Posts: 1215 Location: Buenos Aires, La Reina del Plata
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Posted: Thu Jun 15, 2006 7:00 am |
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Christophe, the technical information available is the one that provides the manufacturer through the data sheets. For this of kind of problems, the help is limited because the complete internal circuit is not available. Anyway I do not understand what is your final interest in knowing why a component fails while itīs working outside specification.
I believe that you would have to direct this question directly to the manufacturer.
Humberto |
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Christophe
Joined: 10 May 2005 Posts: 323 Location: Belgium
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Posted: Thu Jun 15, 2006 7:17 am |
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Ttelmah wrote: | I'd say Tvhhr.
The data sheet requires the voltage on Mclr, to rise from Vdd to Vihh in less than 1uSec. I presume that during the transition, the charge pump does not properly start, and may well overheat. Having a capacitor directly on the Mclr pin, will prevent this from happening.
Best Wishes |
Can you be more clear in your explanation please? I am VERY sure that the 2u2F capacitor is the reason for my PIC dying !
Just tested it out with 100K pull up and RC (390K - 2u2F) and after programming verified all 0000h at all adresses.
After removing the RC network, same problem => PIC dead. |
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Christophe
Joined: 10 May 2005 Posts: 323 Location: Belgium
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asmallri
Joined: 12 Aug 2004 Posts: 1634 Location: Perth, Australia
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Posted: Thu Jun 15, 2006 7:44 am |
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I am not familar with your programmer..
Are you doing a bulk erase?
The 2.2uF could have resulted in the fuses being set to some value other than what you are expecting. For example the protect fuses could be set. _________________ Regards, Andrew
http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!! |
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