jmuellers
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Defective? Blinks 4 long 7 short

Fri Mar 22, 2019 2:31 pm

Hi all,
I registered today to ask the community for help in repairing my Raspberry Model 3B+.
On my desk it was probably exposed to so metal and suffered a short circuit.
I figured that the MXL7704 broke, it seems to be known for not being short circuit proof (actually the part is listed as "not recommende for new designs"...). I exchanged the IC, now the board seems to be powered correctly.
However the green LED behaves as follows:
- flashes once
- flashes four times slowly
- flashes seven times fast
I did not find a description of this pattern anywhere. The list here viewtopic.php?f=28&t=58151 does not distinguish between slow and fast blinking.

edit:
I am using a 64gig SD card with with Stretch (that was working well before), I also tried with a fresh 2gig card with Stretch Lite. In another Raspberry both work fine.

Could anyone help out?

Best regards,
Johannes

jamesh
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Re: Defective? Blinks 4 long 7 short

Fri Mar 22, 2019 2:43 pm

3 flashes start.elf not found.
4 flashes start.elf corrupt.
There something wrong with your SD card, perhaps it has not been imaged correctly.

7 flashes kernel.img not found.
The device has started to boot, but the Operating system image cannot be loaded for some reason. Again, this probably means a badly imaged SD card.

8 flashes SDRAM not recognised.


So, looks like you might have corrupt files on your SD card, but since you have tried a new vcard, that probably means a HW fault.
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jmuellers
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Joined: Fri Mar 22, 2019 2:22 pm

Re: Defective? Blinks 4 long 7 short

Fri Mar 22, 2019 2:56 pm

Hi jamesh, thanks for your answer.
Yeah I've read that section. There's nothing about the slow blinking though, I thought that might yield some additional insight.

If there's something wrong in HW with the SD card interface, I would have imagined the errorcode issued is the one for start.elf, not for the kernel.img. It doesn't seem likely to me that with a defective interface it succeeds to load start.elf and then fails at loading the kernel. Please correct me if that doesn't make sense to you.

fruitoftheloom
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Re: Defective? Blinks 4 long 7 short

Fri Mar 22, 2019 3:17 pm

jmuellers wrote:
Fri Mar 22, 2019 2:56 pm
Hi jamesh, thanks for your answer.
Yeah I've read that section. There's nothing about the slow blinking though, I thought that might yield some additional insight.

If there's something wrong in HW with the SD card interface, I would have imagined the errorcode issued is the one for start.elf, not for the kernel.img. It doesn't seem likely to me that with a defective interface it succeeds to load start.elf and then fails at loading the kernel. Please correct me if that doesn't make sense to you.

I believe Jamesh was referring to GPIO damage ;)
Retired disgracefully.....

jmuellers
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Re: Defective? Blinks 4 long 7 short

Fri Mar 22, 2019 3:32 pm

fruitoftheloom wrote:
Fri Mar 22, 2019 3:17 pm
I believe Jamesh was referring to GPIO damage ;)
Sorry but I don't understand your comment.
The SD card is connected to the ARM with SPI if I'm not mistaken, so I wouldn't refer to those pins as GPIO, right?

I have some experience with PCB design, microprocessors, power supplies, etc. Feel free to offer some more details if you have.
I'm aware that at the price of the Raspberry the cheapest repair is always to buy a new one (my retailer actually offered to exchange it already), but still I want to give it a try.

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rpdom
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Re: Defective? Blinks 4 long 7 short

Fri Mar 22, 2019 3:59 pm

I believe the interface is initially in a reduced mode which just uses one data line. Once bootcode.bin is loaded it switches to the full 4-bit mode and tries to find start.elf. If one or more of the three extra data lines are damaged on the board, or the interface on the Broadcom chip has partially failed, it may be able to get as far as flashing the LED, but no further.

Yes, the pins would be referred to as GPIO. GPIO pins can each be configured in up to 8 different modes including Input, Output and various others (such as SPI or SDIO) depending on the particular pin.

jmuellers
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Re: Defective? Blinks 4 long 7 short

Fri Mar 22, 2019 4:06 pm

rpdom wrote:
Fri Mar 22, 2019 3:59 pm
I believe the interface is initially in a reduced mode which just uses one data line. Once bootcode.bin is loaded it switches to the full 4-bit mode and tries to find start.elf. If one or more of the three extra data lines are damaged on the board, or the interface on the Broadcom chip has partially failed, it may be able to get as far as flashing the LED, but no further.
Thanks for the explanation. Still leaves the questions:
- what's with the four slow flashes preceding the seven fast flashes
- why can it load the start.elf but not the kernel.img

I'll go back to the lab on Sunday and check once more if all supply rails are present. It would be unfortunate if the Broadcom processor did not survive.

jamesh
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Re: Defective? Blinks 4 long 7 short

Fri Mar 22, 2019 4:45 pm

4 long 7 short is a power failure message.

Not sure what exact circumstance can bring up that error, but I suspect the PMIC is dead.
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jmuellers
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Re: Defective? Blinks 4 long 7 short

Fri Mar 22, 2019 8:02 pm

I've replaced the PMIC since it was broken. Before I did that, I powered all five rails from a lab supply, it behaved exactly the same.
I was under the impression that there are no further regulators on the board, right?
I'll let you know after the weekend if all voltages are as expected, I didn't check yet.

jamesh
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Re: Defective? Blinks 4 long 7 short

Fri Mar 22, 2019 9:03 pm

jmuellers wrote:
Fri Mar 22, 2019 8:02 pm
I've replaced the PMIC since it was broken. Before I did that, I powered all five rails from a lab supply, it behaved exactly the same.
I was under the impression that there are no further regulators on the board, right?
I'll let you know after the weekend if all voltages are as expected, I didn't check yet.
It's not possible to change the PMic unless you really know what you are doing, it's a Bga chip on the board. Is that what you did? The error you are seeing is certainly indicative of a pmic failure.
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jmuellers
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Re: Defective? Blinks 4 long 7 short

Fri Mar 22, 2019 9:05 pm

It's not a BGA, it's a QFN. Soldering QFN (or even BGA) is not a problem for me, it's part of my job :)

Since I saw the same error when I used a lab supply (I'm fairly positive to have figured out where to apply which voltage), I figure that whatever killed the PMIC in the first place probably took out something else along the way. :roll:

jamesh
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Re: Defective? Blinks 4 long 7 short

Fri Mar 22, 2019 10:07 pm

jmuellers wrote:
Fri Mar 22, 2019 9:05 pm
It's not a BGA, it's a QFN. Soldering QFN (or even BGA) is not a problem for me, it's part of my job :)

Since I saw the same error when I used a lab supply (I'm fairly positive to have figured out where to apply which voltage), I figure that whatever killed the PMIC in the first place probably took out something else along the way. :roll:
I'll reiterate, the error you are seing is very indicative of a PMIC failure. Not sure if anything else is dead, but the PMIC almost certainly is.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Contrary to popular belief, humorous signatures are allowed. Here's an example...
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jmuellers
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Joined: Fri Mar 22, 2019 2:22 pm

Re: Defective? Blinks 4 long 7 short

Wed Mar 27, 2019 2:58 pm

Hi jamesh,

I have confirmed once again that the new PMIC is operating as expected.
VOUT1: 3.29V
VOUT2: 1.79V
VOUT3: 1.35V
VOUT4: 1.20V
5VSYS: 4.92V
LDO: 3.29V

PP30, which shows the "power good" (PG1) signal, is low, however this is not surprising as it lacks a pull-up and is most probably open drain. The PG2 (pin 20, 10k to 3V3) shows a high level (it's PP15 (RUN)).

PP31: high (GLOBAL_EN)

Is it possible to get more insight about the condition that leads to the blink code? I'm still motivated to try and solve it...

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