my second raspberry has just passed away

spllg

@bearer tried to follow the recovery section in https://www.raspberrypi.org/downloads/ but currently i do not have an empty sd-card. going to order one but i think unless the rpi can boot and operate from usb this will not solve my problem.

reconfigured my printer to operate without rpi - maybe this is an persistent solution although i'm going to lose some workaround.

still wondering what might be the reason for 3 dead rpis.

@spllg you could image a card that is not empty, format it, put the recovery stuff on it, and restore the original content after attempting the recovery as an alternative to ordering a new card.

the pi4 can boot from usb, but weather or not you're able to make the seemingly damaged pi's boot from usb is another matter all together, its just a long shot to determine if the issue is the sd interface or something else.

does the screen show anything when you attempt to boot the dead pi, and is there any difference with or without an sd card?

dc42

I can think of a couple of situations in which the Duet cold send over-voltage to the Pi:

If you are powering a servo for the Duet +5V supply as well as the Pi. Servos inject current into the +5V rail when they decelerate. I've seen Vcc on a Duet 2 rise temporarily to 8V when driving a servo.
If you have a static discharge to +5V, which would typically be from an un-grounded stepper motor body or from the hot end.

spllg

@bearer currently my printer has to print (estimated completition tomorrow evening - late at least half a day). after having finished i will remove the rpi and follow the recovery instructions.

the display keeps dark. maybe i can obtain information via the serial interface .. tomorrow.

spllg

@dc42

no servo but i'm thinking of installing one - how to do this in a secure way?
none of the stepper bodies is grounded. should i ground the steppers?

generally: what additional precautions should i take? what documentation did i miss?

dc42

https://duet3d.dozuki.com/Wiki/Choosing_and_connecting_stepper_motors#Section_Connecting_stepper_motors

@spllg said in my second raspberry has just passed away:

the display keeps dark

haven't tested how the pi4 reacts, but the previous will always display the 4 pixel interpolated rainbow thing before attempting to boot the kernel. it could be different if the boot eeprom is corrupted, but according to the internet the odds of that happening should be pretty slim.

but that you're not getting any output suggest the hdmi driver is done, or the cpu isn't even getting to the bootloader

spllg

@bearer can't get any info from the rpi - green led is unevenly blinking 3-4 times and than is switched off.

going tom buy a new rpi (€60). i will not 5v-power the duet from the rpi and see how long the rpi will be alive - hopefully longer than 4 month. if it will die again i will consider to try another board as i haven't got the time to mess around with hardware problems!

btw.: i remember the rpi freezed several times (days before) before it died.

@spllg said in my second raspberry has just passed away:

@bearer can't get any info from the rpi - green led is unevenly blinking 3-4 times and than is switched off.

going tom buy a new rpi (€60). i will not 5v-power the duet from the rpi and see how long the rpi will be alive - hopefully longer than 4 month. if it will die again i will consider to try another board as i haven't got the time to mess around with hardware problems!

btw.: i remember the rpi freezed several times (days before) before it died.

Buy an Rpi3B+ from a reputable source, use the external 5v in (with a suitable amperage PSU) to provide system power to the Duet-3 which will then push the voltage TO the Rpi (with the correct jumpers being in place on the Duet-3) that combination is 100% working on multiple Duet-3's and has been for months for me with NO issues.

if you still cant work it out I would be willing to purchase the secondhand board from you as you are obviously unable to operate it properly.

spllg

@CaLviNx i could operate the rpi using 5v-power from the duet but i would loose the ability to switch off duet's psu when the print has finished.

if you still cant work it out I would be willing to purchase the secondhand board from you

seems you are looking for a cheap board.

are obviously unable to operate it properly.

ok, it seems, i am unable to operate it correctly after i was able to do so for 4 monthts. wondering what the change could be.

i understand: i'm on my own!

i could operate the rpi using 5v-power from the duet but i would loose the ability to switch off duet's psu when the print has finished.

i think he meant use a 24v/12v for vin and a 5v for 5v_ext supply; as such you could still turn off vin

@spllg

Please correct me if i am wrong but YOU Said (and I quote)

" if it will die again i will consider to try another board as i haven't got the time to mess around with hardware problems!"

logic would dictate that you will move away from the Duet Platform it would leave a perfectly good board not being utilized as you own words (again i quote)

"i haven't got the time to mess around with hardware problems"

So my offer was to assist you in not having to suffer a total loss of the financial burden you endured to purchase the equipment.

I am luckily in a financial position to not seem like i need to be (as you say, and i quote yet again) "looking for a cheap board"

Also if you know what you are doing you can utilize the SBC to automatically control ALL the PSU's when a print has finished, Which Bearer managed to work out.

You also seem to have changed your outlook, previously you said (I quote)

" i feel the duet is somewhat responsible for the deaths"

To now saying (I quote)

"wondering what the change could be"

The Words (I quote)

"i understand: i'm on my own!"

Are factually incorrect, because the FACTS are that numerous users are trying offer you information and some are going as far as to explain things you are not able to work out on your own, so no you are not on your own.

Phaedrux

Now now, we're here to be helpful. If we're not being helpful, don't be here.

@spllg said in my second raspberry has just passed away:

@bearer can't get any info from the rpi - green led is unevenly blinking 3-4 times and than is switched off.

going tom buy a new rpi (€60). i will not 5v-power the duet from the rpi and see how long the rpi will be alive - hopefully longer than 4 month. if it will die again i will consider to try another board as i haven't got the time to mess around with hardware problems!

btw.: i remember the rpi freezed several times (days before) before it died.

i designed this a while back, but still haven't built one to test, mainly because i don't currently have a duet3

https://easyeda.com/bearer/duet36hc-isolator

back to the pi, it'd be interesting to have the boot eeprom removed or re-flashed via spi to rule out that. beyond that i think maybe turning to the pi forums to get help with a postmortem would be the way to go to get to the bottom of what is happening.

spllg

@Phaedrux you mean, i should leave - this is the only support for a €270 board.

spllg

@bearer because the rpi died while printing i do not feel it could be reactivated by reflashing the boot eeprom but i will try it laster.

@spllg said in my second raspberry has just passed away:

@bearer because the rpi died while printing i do not feel it could be reactivated by reflashing the boot eeprom but i will try it laster.

odds are indeed low, but seems the "simplest" option without having it sent off somewhere for more in depth analysis.

there are a couple of test points to check voltage rails, but afaik all are generated from the same chip, so odds are its okay as the green led blinks
https://www.raspberrypi.org/documentation/hardware/raspberrypi/schematics/rpi_SCH_4b_4p0_reduced.pdf

spllg

@bearer isolator: so i assume that the duet is not isolated. unfortunately i did not find this info in the duet docs.

they're not isolated no; there is a series resistance to prevent damage; which seems to be sufficient for everyone else. (i drew the isolator to protect the pi when testing the duet 3, testing finished and duet survived before the board was finished so it was never made)

dc42

Here's an update of our perspective.

We originally designed the Duet 3 5V supply to be able to handle RPi 3B+ plus some power to USB peripherals. Since then, the RPi 4 has become the norm, and it needs significantly more power.
We've seen a few cases of the Duet 5V supply being overloaded. It turned out to be less resilient when overloaded than we designed for. So in revision 1.1 we made some changes, including adding a 3A PTC fuse.
For the future, we're considering uprating the maximum VIN voltage to 50V (so that you can use a 48V PSU). This will mean we need to reduce the 5V current rating, so we would remove the option to power the RPi from the Duet. I think this is reasonable, given the market switch to RPi 4.
We've no reason to believe that there is any problem with the original connection arrangement between the Duet and the RPi even when they are powered from different 5V supplies, subject to the caveat below. However, in order to eliminate any possible issues caused by differing supply voltages, we've added level shifters between the Duet and the SBC interface in Duet 3 revision 1.1; apart from the SS signal, for which we've increased the value of the series resistor to 1K.

Caveat:

It is mandatory that the Duet, RPi PSU, and any PC that the RPi is connected to via USB are powered from the same power distribution block, or double/triple socket outlet. If you don't do this then you may suffer from transients caused by other mains-powered equipment or lightning etc. and poor mains wiring. In addition, if the PSUs of two or more of the devices have a connection between mains ground and output negative, or you connect the RPi via USB to a PC or other device with a ground connection, and one of the output negative connections is poor, then there may be a substantial current in the Duet to RPi ribbon cable ground connection. In particular, if the VIN- connection between the Duet and its PSU is poor, then the bed current may try to flow through the ribbon cable. This is exactly the same issue as explained at https://duet3d.dozuki.com/Wiki/USB_ground_loops.

The RPi PSUs that I have seen do not have a connection between mains ground and output negative. PCs always do have a connection between mains ground and USB common. Laptops often do too, when running from mains power.