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Helpful ReplyHot!PICKIT 4 killing PICs

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Monode
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2019/06/21 03:39:44 (permalink)
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PICKIT 4 killing PICs

Just used a PICKIT 4 for first time. This is on an existing product where I have previously used a PICKIT 2 and PICKIT 3.  On 30 units I had 4 PIC18F2321 failures after programming.  Replaced PICs and carried on as I had a job to complete. Just done a pre shipping check and every unit checked so far has a damaged PIC. The faults did not show during test.  MCLR has a 10k pull up to +5V and on the damaged units sits in the range 1.5V to 3.5V, not 5V.
 
Oddities my end. I don't have VDD on my programming header so have to set power target circuit from tool otherwise the PICKIT 4 (and PICKIT 3) has a hissy fit and refuses to work. PICKIT 4 to target cable is 5 foot long.  Programming speed had to be set to low. Even then it sometimes takes 2 or 3 attempts to successfully erase and program.
 
I had no failures using the PICKIT 3 on the units and all failures occurred after the software was changed and prograsmmed with the PICKIT 4.
 
Any ideas as to the cause of failure?  Cable length?
#1
ric
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Re: PICKIT 4 killing PICs 2019/06/21 03:43:00 (permalink)
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I don't know exactly what is happening, but no VDD on the connector, and a cable more than 200mm/10" are two strikes against your procedure.
I'd try fixing both in the future.
 

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oliverb
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Re: PICKIT 4 killing PICs 2019/06/21 04:21:46 (permalink)
5 (1)
Are you by any chance using a laptop as host, or if the PICkit is being used by itself are you using a "USB charger" as power source? I'm thinking that it is possible to get an unexpected voltage spike on insertion, that has nothing to do with the programming process.
 
 
#3
NKurzman
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Re: PICKIT 4 killing PICs 2019/06/21 04:47:06 (permalink)
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What version of MPLab X?
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NorthGuy
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Re: PICKIT 4 killing PICs 2019/06/21 05:52:18 (permalink)
5 (2)
What kind of damage to PICs do you observe? It has been reported here that there might be an over-voltage on MCLR pin in HVP mode, which kills the PIC's MCLR pin (although that was with PIC16s). See, if PICs get damaged when you program them with LVP. However, for LVP, the PGM pin must be connected to the programmer.
 
Of course, since you use a new firmware, the situation might have been caused by a bug in your firmware as well. So, I would test with the old firmware first.
 
#5
Monode
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Re: PICKIT 4 killing PICs 2019/06/21 06:19:57 (permalink)
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ric
I don't know exactly what is happening, but no VDD on the connector, and a cable more than 200mm/10" are two strikes against your procedure.
I'd try fixing both in the future.
 


 
Can't fix the Vdd in the short term. It wasn't needed when the board was first designed in 2006.
 
I had a look for cable length spec but couldn't find it so thanks for that info. 
 
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Monode
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Re: PICKIT 4 killing PICs 2019/06/21 06:21:16 (permalink)
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oliverb
Are you by any chance using a laptop as host, or if the PICkit is being used by itself are you using a "USB charger" as power source? I'm thinking that it is possible to get an unexpected voltage spike on insertion, that has nothing to do with the programming process.
 
 





Yes, laptop as host. Same one I use with the PICKIT 3.  Is a laptop a known issue?
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Monode
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Re: PICKIT 4 killing PICs 2019/06/21 06:22:19 (permalink)
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NKurzman
What version of MPLab X?



V5.20 downloaded this week, same time as I ordered 3 PICKIT 4s.
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Monode
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Re: PICKIT 4 killing PICs 2019/06/21 06:30:23 (permalink)
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NorthGuy
What kind of damage to PICs do you observe? It has been reported here that there might be an over-voltage on MCLR pin in HVP mode, which kills the PIC's MCLR pin (although that was with PIC16s). See, if PICs get damaged when you program them with LVP. However, for LVP, the PGM pin must be connected to the programmer.
 
Of course, since you use a new firmware, the situation might have been caused by a bug in your firmware as well. So, I would test with the old firmware first.
 




As I noted the MCLR pin is sitting at 1.5V to 3.5V instead of at 5V so over voltage in HVP mode sounds plausible.  Any links on this?
 
Can't LVP as pin is used, don't think LVP was a thing when the board was designed using a PIC16F873.
 
Definitely not firmware.  Some boards were damaged when reverting to the previous issue.
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Jim Nickerson
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Re: PICKIT 4 killing PICs 2019/06/21 08:06:55 (permalink)
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I wonder how your product gets powered with no Vdd when programmed with PicKit 3  and powered from tool ?
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ric
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Re: PICKIT 4 killing PICs 2019/06/21 08:22:30 (permalink)
5 (1)
Plainly it is powered, just they never connected VDD to the ICSP connector.
You can fool the PK3 into working by telling it to provide the same voltage. It sees the voltage on pin 2 and thinks it's connected.

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Jim Nickerson
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Re: PICKIT 4 killing PICs 2019/06/21 08:27:36 (permalink)
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ric,
I had not thought of that, thank you.
Maybe the PK4 senses the current drawn from Vdd when powering from the PK4 ?
 
#12
Monode
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Re: PICKIT 4 killing PICs 2019/06/21 08:38:01 (permalink)
5 (1)
ric
Plainly it is powered, just they never connected VDD to the ICSP connector.
You can fool the PK3 into working by telling it to provide the same voltage. It sees the voltage on pin 2 and thinks it's connected.




Yes, learnt that with the PICKIT 3s.
#13
Monode
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Re: PICKIT 4 killing PICs 2019/06/21 08:39:31 (permalink)
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JANickerson
ric,
I had not thought of that, thank you.
Maybe the PK4 senses the current drawn from Vdd when powering from the PK4 ?
 




Programming works so that is a non issue.  Unless it affects the HVP voltage as it is MCLR pin that is damaged.
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mbrowning
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Re: PICKIT 4 killing PICs 2019/06/21 09:34:20 (permalink)
5 (1)
To add to Northguy's post #5,
There's a note in the  in the Release Notes for MPLAB® PICkit 4 (in MPLABX docs folder, 5.15 in my case)

12.3.2                    PIC16F62X Devices

Possible damage may occur when attempting to program the PIC16F62x devices with the MPLAB ICD 4 or MPLAB PICkit 4. Add a 100 ohm resistor in series on VPP before attempting to program the part with this tool. This part is not recommended for new designs. Devices include:
PIC16(L)F628, PIC16(L)F627, PIC16(L)F84A, PIC16(L)F870/871/872/873/874/876/877
 
Although the note does not mention pic18, the device you are using is also older. I wonder if the long cable you are using is exacerbating whatever problem caused the PIC16F62x failure and causing your failure. Maybe the series resistor in MCLR/VPP would help.

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Monode
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Re: PICKIT 4 killing PICs 2019/06/21 10:42:17 (permalink)
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mbrowning
To add to Northguy's post #5,
There's a note in the  in the Release Notes for MPLAB® PICkit 4 (in MPLABX docs folder, 5.15 in my case)

12.3.2                    PIC16F62X Devices

Possible damage may occur when attempting to program the PIC16F62x devices with the MPLAB ICD 4 or MPLAB PICkit 4. Add a 100 ohm resistor in series on VPP before attempting to program the part with this tool. This part is not recommended for new designs. Devices include:
PIC16(L)F628, PIC16(L)F627, PIC16(L)F84A, PIC16(L)F870/871/872/873/874/876/877
 
Although the note does not mention pic18, the device you are using is also older. I wonder if the long cable you are using is exacerbating whatever problem caused the PIC16F62x failure and causing your failure. Maybe the series resistor in MCLR/VPP would help.




Thanks for that.  The PIC16F errata states:
"Voltage spikes below VSS at the MCLR pin, inducing currents greater than 80 mA, may cause latchup. Thus,

a series resistor of 50-100Ω should be used when applying a “low” level to the MCLR pin rather than pulling
this pin directly to VSS".
So it sounds like the PICKIT 4 can take MCLR below 0V.
 
At least adding a 100 ohm resistor to our programming leads is a simple solution.
 


 
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Monode
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Re: PICKIT 4 killing PICs 2019/06/21 10:43:19 (permalink)
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Thanks guys/gals.  Looks like problem solved. At least until the 100 ohm doesn't work.
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NorthGuy
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Re: PICKIT 4 killing PICs 2019/06/21 10:46:30 (permalink)
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Monode
As I noted the MCLR pin is sitting at 1.5V to 3.5V instead of at 5V so over voltage in HVP mode sounds plausible.  Any links on this?

 
I cannot find it now. There's a poster here - Howard Long. He made extensive tests, and this is what he found - overvoltage over 20V, then drop below VDD - similar to your pattern. You can search for his posts on the subject.
 
You can try with a series resistor on MCLR - 100 Ohm or so. This will not revive the old ones, but new PICs will be safe.
 
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PStechPaul
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Re: PICKIT 4 killing PICs 2019/06/21 20:08:51 (permalink)
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Perhaps the long programming cables have enough inductance to cause a voltage reversal when Vpp returns to zero at the PICkit. Also, the PICkit4 may have components that switch faster than the older PK3 and PK2. The MCLR/Vpp pin can't have a protection diode to Vdd because of the need to raise the voltage for HVP. And perhaps there is also no diode to Vss, or it is not a sufficiently fast diode to clamp the voltage to Vss-0.6V. A Schottky diode would be better.

 
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rpg7
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Re: PICKIT 4 killing PICs 2019/06/22 05:19:59 (permalink)
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PStechPaul
And perhaps there is also no diode to Vss, or it is not a sufficiently fast diode to clamp the voltage to Vss-0.6V. A Schottky diode would be better.

A diode in the PicKit 4 would have no effect.  The cause of the problem is that fast transition  from 5V (or higher) is reflected when it reaches the /MCLR pin and because it is unterminated the reflection is negative for a falling wave. The 100 ohm (nominal) resistor essentially performs as a series terminator at the source or a current limiter if placed at the PIC
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