CircuitStudio: SDRAM Routing impossible? €10000 Upgrade? KiCad?

Question

Hi there,

I'm hoping that someone can point me in the right direction. I started learning about PCB design roughly 4 weeks ago and I've since designed a small power supply and a camera sensor breakout board. I purchased CircuitStudio and so far I was happy with it.

Now I am trying to connect a $5 STM32H723 with a $2 IS42 SDRAM chip. All the Altium articles are pretty insistent that I'll need length matching to make sure that the different data lines have the same delay between the SDRAM and the CPU, e.g.

https://resources.altium.com/p/how-do-pcb-trace-length-matching-vs-frequency

https://www.altium.com/solution/ddr3-routing-guidelines-and-routing-topologies

But from what I understand, length matching is not supported in CircuitStudio. I did find the Accordion workflow, but that requires me to route one wire after each other by hand and to keep track of all line lengths myself, so it's not really practical. Still, I kind of expected that CircuitStudio would include what I need and since we're talking about connecting two low-cost components on a PCB that I can still solder at home, I feel like this has to be possible with CircuitStudio somehow. But I really couldn't figure out how.

Anyway, so I asked Altium for an upgrade quote and they said going from CircuitStudio to a permanent Altium license will be roughly €10k. For a beginner and hobbyist like me, that is of course way out of my price range. Also, that seems insane. The cable from a $5 CPU to a $2 RAM chip will cost me $10000+ ???

I read that the ICEZUM Alhambra board designer

https://github.com/FPGAwars/icezum/wiki

ran into a similar issue in 2017 and they used a tool called altium2kicad

https://github.com/thesourcerer8/altium2kicad

to migrate the entire project over from CircuitStudio to a free software called Ki-Cad and then used that to finish their board design.

But I feel like I must be overlooking something here because it seems super weird to me that a free tool from 5 years ago would support SDRAM routing, while the self-proclaimed EAGLE alternative from Altium cannot?

So how do others do their RAM routing with CircuitStudio?

michaelkellett · Answer

First off, obviously your purchase of the Circuit Studio license was a mistake. It's done now and you will need to move on. In my experience cut down versions of a company's major product are rarely satisfactory, every enhancement they put in the "entry level" loses them some sales from the core business so such enhancements are rare. I don't use Kicad bu it does have a good following and many people seem to like it. It's free so that's a very definite plus. You do not need matched length traces to interface SDRAM to a micro with an SDRAM controller at modest speeds. I have not done this for an STM32H723 but I have on several occasions with FPGAs. Keep the tracks short and as direct as possible. Don't try and run it flat out at maximum speed. I have not studied the STM32H723 in detail but it looks as if you should have no trouble reducing the SDRAM clock to well below 100MHz shoudl you wish to. The picture shows an SDRAM in TTSOP package connected to an FPGA in TQFP144. Careful selection of FPGA pins allows the whole thing to be routed on one layer with no attempt at track length matching. This layout would work with 100MHz SDRAM clock , although in the actual design it ran at 25MHz to save power. MK

hugohu · Answer

I first used EasyEDA for my design and quickly realized the limitations of it. Changed to KiCAD, learned it in less than a week(still being a newbie) and completely transitioned my projects in less than 3 weeks. EAGLE is a good choice but it has limits as well. KiCAD is actually quite well documented with 3rd party tutorials and I definitely think I saw a length calculator for it somewhere. There are bugs, but it's better than paying 10 grand, is it

fxtentacle · Answer

You might have implicitly said why this situation feels so frustrating to me: I'm new to this so I thought an entry-level product will help me not be overwhelmed and get things done. But all the documentation that I can find tells me how to do things in Altium Designer, not in CircuitStudio. So I try to imitate what the tutorial videos say and then I get stuck because I need a feature that is missing from CircuitStudio. If CircuitStudio had good instructions on how to do length matching manually, I would have tried that. But I only found a tutorial on Accordion length adjustment but that one didn't work when I tried to follow it. And yes, you're asking a very good question: "What will happen to your STMicro and SDRAM system, at the speeds at which you are working at, if the length matching isn't precise?" I honestly have no idea. I read the Altium tutorial and it says I need to care above 100 MHz. The STM32H7 has an integrated SDRAM controller running at 240 MHz. So I presume I need at least some level of length matching, but I surely don't know how precise exactly. I was kind of hoping that the app I'm using would have a wizard or calculator for that. And yes I agree that KiCAD looks a lot more like the full Atlium Designer than like CircuitStudio. Apparently, it can do everything and more, but it'll have a steep learning curve. That said, my learning of CircuitStudio has also been pretty bumpy so far, due to the lack of dedicated tutorials. It feels more like I'm training for the day when I can finally afford to upgrade to Altium Designer, but I doubt I'll ever reach that day as a hobbyist. And to add insult to injury, it appears that the KiCAD forums are full with active users. I tried to see what people were having trouble with and they had like 1000+ new posts throughout this week. Over here, you're the first person to say anything in 6 days There's also other issues: When I purchased CircuitStudio, it was advertised as if I could fully download it and backup it locally and install it offline. For me, that's very important because I do not want to run into the situation that I cannot open my design in a year from now just because someone decided to turn off the old licensing server. So I emailed support roughly 2 weeks ago to ask for the promised installer ... and also didn't get a reply yet.

CircuitStudio: SDRAM Routing impossible? €10000 Upgrade? KiCad?

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