Electronics > Projects, Designs, and Technical Stuff
Software/Controller development questions/advice.
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gonzalito:
SD card might be an issue in the long run.
I added a video of the machine we are prototyping. This has all the main features we want, but we need it to be smarter, so that was why I was wondering about the raspberry.

We are now intending to make this thing smarter so we can go out and sell at least 5 in the short term..
rstofer:

--- Quote from: Jeroen3 on September 12, 2019, 02:16:59 pm ---PLC's also don't suffer from defective SD cards every few months.

--- End quote ---

This is a SERIOUS problem with Linux and particularly on the Pi and similar platforms.  Any loss of power without a previous shutdown command will very probably break the file system.  Data WILL be lost, blocks will be unlinked.  It's a mess!  This is pretty easy to control on a desktop or laptop where power is never just shut off.  It is not so easy to control in an embedded environment.

I have a couple of Pi 4 systems, one of which I like to think is important, so I bought a small UPS to keep it alive for a few hours should we experience a power outage.  If I'm home, I'll simply do the shutdown procedure.  In any event, all of the important files are saved on my NAS box.

Keep backup images of the SD card!

There must be a way to avoid this but I'm not up to speed on Linux file systems.

I wonder if a tablet computer would make a good HMI.  Cypress makes a very powerful PSoC6 uC with BLE that could be linked via bluetooth to a cell phone or tablet.

Here's a link to the PSoC6 videos:

https://www.cypress.com/training/psoc-6-101-chapter-1-getting-started-psoc-6-mcus
rstofer:
Re: the video, is that HMI weatherproof?   That may be hard to replicate.  Leaving the PLC in place is probably the best option.  All that stuff works.  Add a Pi for the management but leave the low level controls as is.  Except for cost, of course!
SiliconWizard:

--- Quote from: rstofer on September 12, 2019, 02:57:33 pm ---
--- Quote from: Jeroen3 on September 12, 2019, 02:16:59 pm ---PLC's also don't suffer from defective SD cards every few months.

--- End quote ---

This is a SERIOUS problem with Linux and particularly on the Pi and similar platforms.  Any loss of power without a previous shutdown command will very probably break the file system.

--- End quote ---

Nah. Fortunately, reasonable journalling filesystems have been standard on Linux for a long time now.
If you're on ext4, the probability of breaking the FS after a power loss (or any hard shutdown/reset of the system) is very low. I've never experienced any major issue with that.
Sure the very last written files occuring just before or while the power loss occurs may be only partially written or not at all, but it won't usually break the FS itself.

Now some SD cards' controllers are very lousy actually, and may themselves make their content corrupted in case of sudden power loss, but it's not related to the FS. Never experienced a single "break" of an EXT4 system on any HDD.

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