Anybody doing ARM-MPU designs? Like LS1012A / LS1046A - Page 1
Forum section: electronics / projects

author: homebrew
author_rank: Frequent Contributor
timestamp: March 08, 2021, 04:59:08 pm
content: Browsing some distributors' MPU inventories I came across very interesting ARM cpus. However, I hardly find any (open) designs using it. These CPUs/SOCs should be rather interesting - SATA, 1G/10G ethernet, several lanes of PCIe, USB3.0 ... so quite powerful stuff. And you can order them in quantities of 1. They have been around for some time now but seemingly do not attract a lot of attention in communities like this forum, although they seem MUCH more capable than all the Raspberry based stuff.So, how would you rate the chances of getting a board up and running without a $100'000 development environment?Would such an endeavour have ANY chance of success without expensive simulation, CAD and test equipment?Certainly I would need to do my homework on DDR4 layout and design. That one scares me the most ... (especially all the manual length matching in KiCad). I've done SATA, HDMI and USB differential routing successfully before but at these speeds and tight margins it seems new territory.What are your thoughts? Is it even worth trying as a non-proffessional or doomed to fail right away?

author: wizard69
author_rank: Super Contributor
timestamp: March 09, 2021, 04:38:32 am
content: Well personally I'd have no use for the series in the subject line. Mainly because there is not display processor / GPU support. Thus at this moment in time I'd have little use for such a chip based board. Maybe the i.MX 8 series but they are starting to show their age. TI's Sitara processors are interesting considering they have hardware suitable for running realtime code in parallel with Linux. Not much in the way of a GPU though (they have one but not something to get excited about).I look at it this way, if you are going to build something similar in scope to a RASPBERRY PI you need to have a bit more to offer. A realtime processor that is better than an /Arduino could be very competitive. Similar to PI I think the need for Hi speed ports isn't as great as you might imagine. The whole idea with these boards and the similar is to plug in the customization into the main board. You would need to do a decent high speed RAM solution, the video support and hopefully an M.2 slot, hopefully the reference designs and developer info would help there.You don't want a lot of I/O anyways to keep the card cost down. Frankly a well implemented, old fashion, RS232 port is still a thing in the embedded world. If the completed board, with 4 -8 GB of RAM, sells for more that $50 you are likely in the wrong market. The PI world gets excited when they have boards that cost more than $30.I don't know if the TI hardware is available in low volume but I suspect that the lack of boards indicates an issue there. I just don't see huge potential for a board based on those networking chips. The mix of hardware is less than ideal and costs are likely to balloon to compensate.Quote from: homebrew on March 08, 2021, 04:59:08 pmGetting people to pay for capability is always a problemQuoteIt probably could be done. It really depends upon many factors including how well the manufacture documents the hardware. The more stuff integrated on the SoC and in package the better. The problem here is I don't believe anybody is selling the SoC with in package RAM in low volume. The obvious thought is the fewer high speed things you are responsible for the more likely you can do a design in reasonable time.QuoteYou will need at least something resembling an electronics lab. What is expensive is kind of a joke as it depends upon if you ask your wife. As for what can be done, start looking in forums for low end CAD systems and see what people have accomplished with those tools.QuoteThat is why the ideal solution is to consider SoC with in package RAM. Minimize high speed design. The only thing that the competition really comes up short on is I/O to secondary storage. In an ideal world there will be a PCI-Express based M.2 slot.QuoteYou don't learn anything without trying. I believe you can do it but having a lot of experience, the right tools and patience to go through many revisions is required.

author: homebrew
author_rank: Frequent Contributor
timestamp: March 09, 2021, 07:57:25 am
content: Thank you for the elaborate answer!Quote from: wizard69 on March 09, 2021, 04:38:32 amYes, I've looked into these, too but I need fast I/O (e.g. SATA/NVMe/gigabit Ethernet) and certainly no GPU. So just looking into the specs they seem to be a perfect match for my requirements.Quote from: wizard69 on March 09, 2021, 04:38:32 amI certainly do not intend to compete with the RPi folks. This was just for reference. The RPI compute module 4 now does have at least one PCIe line accessible and one USB3. But no SATA, and just a single gigabit Etherenet.Quote from: wizard69 on March 09, 2021, 04:38:32 amAt least one such chip seems to be available: SAM9X60D1G-I/4FB (Mouser, Digikey and Farnell seem to have them stocked).Here is an excellent read-up on many of those options:https://jaycarlson.net/embedded-linux/However, none of these chips meet my requirements on I/O (storage, network) performance.Quote from: wizard69 on March 09, 2021, 04:38:32 amObviously - and I do! However, there is a BIG difference if you have a scope with 100MHz bandwidth and one with several gigahertz. The latter I don't have. Likewise CAD/simulation. Practically, I'm bound KiCad - cost-wise and because I'm absolutely fluent in using it. And here is the thing - I've not come across any DDR4 design with multiple chips (fly-by / point-to-point topology) done in KiCad.Quote from: wizard69 on March 09, 2021, 04:38:32 am"High" performance SIPs are probably not available in low volume so for now the DDR4 elephant stays in the room. With the LS10XX, PCIe-based M.2 storage should be doable, however only with one (PCIe 3.0) lane. But this would still give a fast access to storage.Quote from: wizard69 on March 09, 2021, 04:38:32 amYes, and that's why I've done a lot of challenging (to me) things in the past successfully even as a non-professional. But this seems different. You cannot learn to fly by jumping off a building. You will just end up falling. Patience and revisions is a given but my concern is that I will have no chance of debugging errors due to marginal designs. What if the board crashes randomly after 1 hour?That means that some portions of the design must work on first try. DDR4 is one of them. If it doesn't work and it was not for an entirely stupid, identifiable reason, I would never be able to point down the root cause and improve the design iteratively. I would just continue wasting money in 0.5K$ increments ...