Selecting a processor platform for industrial products

Cloudfree recently emailed this update:

Raspberry Pi Shortage Update

Unfortunately, it seems that Raspberry Pis won’t be easy to get a hold of any time soon. Our supplier of Pis, Newark, continues to push back lead times.

We still wanted to give users an easy way to run Home Assistant on so that even first time users can get up and running with their CloudFree gear, without having to wait months (as with Home Assistant Yellow) or even years.

That’s why we have put together the CloudFree Black Hub. These machines have 3.5x the processing power of the Raspberry Pi 4 and utilize SSD storage for better speeds and reliability than microSD cards. They come preloaded with Home Assistant OS and have integrated Bluetooth to gather data from any Bluetooth sensors you may have around the house. These renewed Dell Optiplex machines pack a lot of power in a small package and come with a 1 year warranty. Visit the product page to get notified when more are available.

One of my customers is using a Variscite DART-6UL, and recent lead time is 20 weeks, not great, but not impossible like the rPI. i.MX SOM modules are more expensive than rPI products, but a lot of people right now are glad they designed in industrial i.MX processors instead consumer/maker class stuff. A few advantages I see in using i.MX processors for industrial products:

  • they are more reliable. Every product we’ve ever done with i.MX processors has been rock solid. I’ve had a lot of SD card corruption problems with various rPI models (their CM4 products may be better).
  • software support for i.MX processors is good and tracks mainline OSS projects (Linux kernel, Yocto, etc.) fairly well.
  • there are quite a few SOM vendors producing i.MX modules. If one goes out of business, you could switch to another with a minor re-design.
  • products using i.MX processors tend to be industrial as these processors are slightly too expensive for consumer products, so you don’t get hit with supply issues due to high volume consumer products sucking up supply (I suspect this is what happened to rPI products).
  • i.MX SOM vendors are geared for reliably providing products to industrial customers. rPI and other maker grade products are stocked by various online stores, but supply and leadtime is often unknown.
  • i.MX processors have long production life-cycles, unlike processors designed for consumer products where they may be dropped at any time once consumer demand goes away. Maker class SBCs often use consumer grade processors.

rPI and other maker products have contributed greatly to the embedded Linux ecosystem in providing powerful low cost platforms – many good things have come out of their existence, however be careful basing your industrial product on them. They are designed foremost for low cost which is great for one-off maker projects, but industrial reliability and production supply is a secondary concern.

I imagine a good bit of the reason for this is due to availability of documentation. The Raspberry Pi foundation has not had a great track record of putting out good and complete documentation on their SOCs. Contrasting with NXP/Freescale or TI, who put out quite good documentation, is one reason why it’s much easier to send changes upstream if you don’t work for the silicon vendor itself. Without docs, it’s hard to know how a thing works so it’s hard to send patches.

The Raspberry Pi foundation seems to have heard this frustration. Although they don’t offer nearly the silicon lifetimes of traditional industrial SOC vendors, they have gotten significantly better over time.

I’ve only had 1 product that I’ve ever worked on where a SOM was the right move. Every other product I’ve worked on it was clearly the right move to fully design a SOC into a custom PCB. I think it really depends on the sales volumes and interfaces you need on the SOC which decides the correct way to go. I’m actually surprised that the SIP products (single BGA incorporating SOC, memory, and some power converters) hasn’t become more popular, but maybe I just don’t see it because the things I’ve worked on aren’t the target market.

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Probably also depends on the relative complexity of a SOC/RAM/Flash/PMU design compared to the rest of the board. In your case, I’m guessing the rest of the board was complex as well (high speed design, etc). Many of my customers of coming up from MCU designs, so a SOM reduces some risk.

I worked on one project that used a Microchip SIP – in this case, the SIP was still fairly expensive, and did not add a lot of value in my opinion as the challenges we faced were in power supply, etc. A Variscite SOM seems to be much higher value as they are cheaper and integrate more stuff (WiFi, Flash, etc).

Should also note that Microchip, TI, and ST also make processors that run Linux that are a good fit for industrial applications. NXP i.MX seem to be the most popular with SOM vendors. Especially the i.MX8 lineup – they have a broad range of parts available.

That’s interesting. At my previous job we had looked at some of the Microchip SIP offerings and the prices were very competitive with doing a custom design with stand alone SOC and memory. Possibly this was due to volume discounts (we weren’t buying from stocking distributors).

Yes, we had somewhat complex designs, but the main thing was just that some interfaces on more advanced SOC are often not broken out correctly on a SOM. For example, on the TI AM57xx series SOCs it’s uncommon to find the video ports to be properly broken out to the SOM interface connector. But one of the key uses for this family of SOC is for video input and processing with the DSPs.