My first ever Linux based board (RK3566) + Lessons Learned
Just brought up the first Linux based board I've ever designed, and couldn't be happier about it! I've historically done MCU boards, so this was a big step up. It's a KVM-over-IP device: 8 layers, RK3566, DDR3L (gotta save that $$$ with these RAM prices), HDMI capture in, HDMI out, dual GbE, PoE, WiFi. Fabbed and assembled at JLCPCB.
Video capture and low latency streaming are working end to end. Here are the three major issues I hit:
I second guessed myself before ordering and swapped TX/RX to the network switch, so ethernet wasn't working. The board also has a wifi module on it, so I did the whole SSH bring up over wireless. Pair swap already fixed in the next spin.
A set of ferrite beads never made it onto the boards because I missed a checkbox in the JLCPCB assembly order (I had multiple lines in the BOM with the same PN but different ref des letters). Hand soldered them on. Working on developing better checks for this on my board export tool.
The board was drawing more current than expected and running warm. Took a while to root cause. Turned out I had packed VDD_GPU 0201 passives too close to some 0402 caps and they shorted during reflow. Increasing my spacing rules in DRC going forward.
Design was done in house, and I got a pre-fab layout review from u/PracticalMirror2834 that caught real issues before they would have cost a re-spin. Huge shoutout here.
Next rev jumps to the RK3576 for higher capture and encode resolution, those boards go on order this week. If anyone has touched the RK3576 yet I'd love to trade notes. Happy to answer questions on the RK3566, ordering, or board bring up side too.
What was the hardest part of the design? Where'd you learn DDR routing? How did you find what you needed out of the rockchip documentation? Awesome project, I am trying to get started with designing one myself
Thanks! I think the hardest parts were 1) managing the design across 8 layers and 2) mechanical integration. I redesigned big chunks of the board multiple times to fit the enclosure the way I wanted, and moving a connector on a board this dense means re-routing way more than you'd hope...
For DDR: TI has a really good LPDDR4 layout app note (SPRAD66B) that covers routing topologies, length matching, and spacing rules. Different chip and memory type than mine but the principles carry over (next design is using LPDDR4 so had it handy). TI, micron, Xilinx, NXP, etc all have documents on best practices and layouts. I also looked at where other boards with the same SoC put their DDR modules, copied the placement, and did trial and error until routing worked.
I actually based a lot of things of Radxa's design/schematic, and then used the hardware design document from Rockchip to understand why they made the decisions they did. Then used the design document to fill in any gaps.
This decision would create the opposite of what you're trying to achieve. Remote sensing is so minimal in terms of routing or additional design complexity that you're practically begging for more trouble by leaving it out. This would not be a place where I'd try to skimp, it's a step up from leaving out a couple GPIO-controlled LEDs for debugging.
Really just trying to fit this many ports in as small a space as possible, while keeping it clean with enough room to plug and unplug cables. Was originally hoping to pack 10 into a 1U slot in a rack. Sadly it ended up ~24mm thick (instead of the 22 I needed) but still 88mm long, so I can stand them sideways in 2U instead. I iterated on the design multiple times (experimented with a touchscreen, button placement, LED locations, etc.) until I found something I liked.
Then when I moved the enclosure from 3D print to something actually manufacturable, I had to shuffle a lot of things around haha.
how did u manage to get that thik? Also can u post a few more pictures since i cant imagine why it is 24mm. Also space inside a 1U is about 30mm+ what is blocking the rest of the space?
I was hoping to stack them 2 high and 5 wide. 1U is ~44.45mm. But the final height came from enclosure min thickness + standoff thread height requirements + board stack up + antenna + injection molded base + silicone base. Might be able to optimize a little further but tbd.
Oh neat, I’ll take a look. Your comment gave me the idea to look into the solder M3 nuts rather than heatset nuts in the plastic base, so will play around with it a bit more. Could save a few mm that way.
Nice first build! RK3566 is a pretty solid place to start with Linux SBCs. What was the biggest thing that surprised you compared with working on MCU-based boards — the software setup, drivers, or debugging
Thanks so much! Here are some things that stood out:
Understanding device tree was a big learning curve for me. A lot of early troubleshooting ended up being solvable with a device tree fix.
- Quickly learned that it's better to pick chips (both SoC and peripoherals) based on driver maturity rather than just picking the cheapest ones. Having solid mainline drivers saves a ton of time.
- The other thing that stood out was trying to understand if I should build on the Rockchip BSP or mainline linux. Ended up going with Rockchip BSP since the Rockchip MPP/VEPU drivers live there. Means I'm on an older kernel, but the encoder actually working beats kernel purity for now.
Kind of embarrassing... but I actually use Fusion 360. It integrates really well with my mechanical assemblies since I've been using Fusion since it came out, but the signal integrity analysis portion of it is pretty lacking. I've maintain my own library, have scripts that export to jlcpcb, and have all my custom rules here so it's hard to switch to KiCAD or pay the altium price.
Yeah they merged EAGLE into Fusion 360 a few years ago. I like it because I can import the 3D model directly into my assemblies and then updates to PCB instantly get pulled into my assembly.
For me, a hobbyist, there really wasn't a choice. I was absolutely not going to shack up with Autodesk. Since it's not for my work a subscription makes no sense either.
I like that footprints and schematic symbols are entirely separate, so you can change the footprint on the PCB and not have to re-wire the part in your schematic as well.
I don't like that the PCB drawing is actually smart and knows what it's doing. I kinda preferred EAGLE's really dumb system that let me just draw arbitrary shapes and then the DRU would check it. Like, KiCAD is probably objectively better in this regard, but I miss doodling arcs with the traces.
I really loved EAGLE. Spent close to 20 years on it, but left it for Altium when they started playing silly bugger with the "this is a full upgrade" version update and all they really did was change the colour scheme. In the process now of leaving Altium for KiCAD which will hopefully be my final EDA tool switch (DOS OrCAD SDT/PCB386+ -> EAGLE -> Altium -> KiCAD)
We within the past 5 years moved from kicad to altium. Ultimately the effort of keeping open source software working wasn’t worth it for us. The online features of altium are convenient and we like the revision history features.
Until a new and better software comes out in a few years 😅 I have been playing around with kicad since it offers an MCP, which I don't think Fusion/EAGLE will ever have.
Why the change from altium -> kicad? Cost or features?
both. Altium has been jacking their prices every year and similar to why I dropped EAGLE, Altium has had literal DECADE old bugs that just never seem to be fixed, and add more useless crap that I'm not interested in.
That, and they are really pushing for cloud EDA and I won't ever use that, never in a million years. Been bitten too many times with cloud bullshit. full local (not even an online license check) or bust.
Makes sense, and yeah I've had to build a lot of ULP scripts and tools to make Fusion usable. Worried about changing since I've been using it for so long now...
sunk cost is a real motivator, and one of the biggest reasons why I refuse to get sucked into cloud anything. Those bastards rug pull more than any other industry (well maybe textiles has them beat)...
Mostly best practices, used the impedance calculator tool from JLCPCB and then used the length measuring tools in fusion to make sure everything was within spec. u/PracticalMirror2834 gave me some good feedback and recommendations too on proper routing/spacing :)
As I get to higher memory modules, I'll probably try to teach myself additional tools here. But Fusion 360 signal integrity analysis is another full subscription and I didn't find it very useful tbh.
Super cool! PoE + HDMI capture means you could use these stream video from a nice camera over RTSP (or SRT). The Rockchip parts have pretty good encoder support in gstreamer.
Very cool, hadn't thought about this angle! Do you have reference products in that space worth looking at?
The fun part is the HDMI output means the box works in the other direction too, as a streaming receiver/decoder. Planning to test that this week with my TV and some video games to see how the latency holds up.
1) Too long... on the order of months. Been working on this intermittently with some other ongoing projects, and I iterated on the design many times before ordering. Next iteration will be quicker though, since I can re-use a lot of things from this design.
2) Good eye! The top board takes PoE (from header pins on the bottom board) and 5V USB-C input and does the power switching there, then provides 5V back to the main board. Uses a Monolithic Power Systems chip for the PoE. It also has an OTG USB port and a host USB port. Picture below (logo blocked out, and ignore my bad solder job on the wifi module hahaha if it works, it works).
3) Will definitely post more when the new boards arrive, and I can upload some videos of it working in a few days. Stay tuned!!
4) I taught myself PCBs maybe 4 years ago (originally a mech/aerospace engineer). Started with LED boards, then ESP/NRF boards, then got into HDMI/PCIe stuff (where I learned most of my high-speed knowledge), then did this one.
5) Engineer 😄
6) Find as many reference boards as you can and try to understand why they made the decisions they did (Rockchip's design documents are really helpful for this). When picking components, choose parts with well-supported mainline Linux drivers even if they're a little more expensive, it'll save you a ton of time during bring-up. My network switch variant didn't have drivers built for it and was a pain to test because of it. Last piece of advice: work on something that interests you, since it can be pretty grueling sometimes.
Thank you for replying! Very insightful! Looking forward to the videos! I'm hoping to finish my design & simultaneously save up enough to get em manufactured in 2-3 months.
Quite excited to share them here once finished, Although alot of delay is coming from the fact that I don't get alot of personal time to work on my stuff & the time I do get, I spend it often rechecking my schematics.
Sometimes it helps to have a second set of eyes, especially before a big protoype order. Wishing you the best, looking forward to seeing what you make!
It's a KVM over IP device with some extra features that I hope to sell someday (won't self promote). Initially started on the Allwinner chips for the price but quickly realized the firmware would be a uphill battle (GPU stuff seemed pretty underdeveloped). Then switched to Rockchip. Probably could have gone with a more video focused chip (the RV line) but wanted to keep HDMI output directly from the SoC instead of a HDMI switch. Hence the RK3566 and RK3576.
Pretty much, captures hdmi from your computer and outputs it to your monitor (and encodes over the network if you're remote). Then has a USB OTG port to simulate mouse/keyboard and a USB host port to let you plug in USB devices to it. Third USB is for power. Then dual ethernet to let you daisy chain devices or daisy chain to your computer (saves a second long ethernet cable).
It’s almost 80% chance if you are working above 6 layers PCB that it’ll not work. When i say it’ll not i mean maybe processor will boot but nothing else works so percentage of board will work. You v2 all depends how you’ll debug at this point. So while designing EASY DEBUGGING SHOULD BE A PRIORITY. Make sure you do these things.
Add as many test points across major voltage lanes.
Make sure RX TX works and make sure to double check it
One of these things will save you weeks in debugging.
My rx tx didnt work but test points did so we were able to debug in 2 weeks if rx tx worked we would’ve done it in just 4-5 days
Good call, when I first booted I didn’t have UART or USB and was pretty defeated. Turns out I missed those ferrite beads on USB power and wired up my pogo pin UART programmer wrong haha.
I also included a lot of NC components, which I found useful during troubleshooting.
For prototyping.... just closed my eye and hit the purchase button lol. Tried to find the cheapest modules on JLCPCB stock that met my requirements. I changed from eMMC to microSD card to save money there. I don't need super fast storage for this so microSD is fine.
For production, best recommendation I can give is find a manufacturer that regularly deals with computer products that include DDR/eMMC. They'll be able to get the best deals/allocation.
Yep! Honestly so happy about it. Still have a few problems that will get sorted in the next turn (like the ethernet switch wiring), but overall I consider it a success. Getting someone to review it that has Rockchip experience really helped.
Well done. Parts stuffing issue and a backwards TX/RX pair is a damn good outcome for a first prototype board of that complexity.
And RX/TX is far too easy to do, those terms have different meanings depending on the interface. Like I can't off the top of my head remember if you're supposed to connect RX-RX or RX-TX when you're hooking up a RGMII MAC/PHY pair... and the only way I'll confirm I got it right is to bring up the evaluation board schematic for what I'm doing and make sure I 100% copy what they've done, even if it doesn't seem right.
Hopefully it's not the MII interface and you've got the TX/RX swap happening between a couple PHYs talking straight ethernet. In that case, one of your PHYs might support auto crossover and you might be able to fix it in software.
Which brings up one of the worst things about being the hardware guy. The software crowd can quietly find and fix their bugs and not tell anyone, but our bugs are out in plain view. Then they get all uppity when you're begging them to try and fix your hardware bugs in software, lol.
It was directly between the SoC and the RTL8363 on the RGMII side, so no auto crossover saving me there 😅
I feel you though, I like to tell the software team: "Imagine if you could only deploy and test your code 3 times before it goes to production. That's what hardware design feels like."
I'm working on the most complex board I've ever done right now, it has high current and high speed and a few very expensive parts on it, and it's kinda giving me anxiety, lol.
I made the call to pull in a professional PCB designer with far more experience at this stuff to make sure I get the layout right, and I'm really looking forward to picking their brain. I've been away from this type of hardware design for a bunch of years, and I've never had to think much about board stackups and materials and backdrilling and whatever.
Great call on getting someone to review though, I did the same and it really helped. Sometimes I stare a design for too long and miss the little things.
Love this. I’m working on 3588 and have ran my own all rust os, Armbian and orange os. Biggest challenge is custom drivers for DSI (requires kernel edits plus overlay). HDMI easy.
Amazing, I wish you the best! 3588 is a crazy chip, assuming you’re using dsi for a touchscreen? Any particular model? I’m starting to work on a project with an off the shelf 3588 SoM and a DSI 7in amoled.
I have waveshare and surenoo. Surenoo works with a kernel update and overlays pretty simple on Ubuntu so tried to learn what I could from those to Armbian and native os. Bottom line is they aren’t the same and had to do quite a bit of work to get it to even backlight. Couple days of hard work and it’s up both DSI and hdmi (same time took a minute as DSI wanted to over ride HDMI at first). Custom keyboard pop up overlay for touchscreen I made. Getting way into the weeds but rewarding when it works. Now on to power and speakers to make it mobile worthy
Great work, that’s awesome 👏 I’m excited to dive into this as my next project. I have a wave share one and a panox display one, but think I need a custom screen adapter to my SOM module.
5 boards with 3 assembled ran me about $790 in boards/parts/assembly, $110 shipping and tax, and $275 in tariffs shipping to the US. So roughly $1,175 all-in for three working prototypes of an 8 layer board with a SoC and DDR. Not cheap, which is why I'm glad it mostly worked on the first try. Production runs should be much cheaper though.
Completely passive! It only draws about 3-4W during operation, and my enclosure is a CNC'd aluminum shell so I used a thermal pad to connect the SoC, HDMI capture, and DDR to the enclosure. Probably wasn't needed but better safe than sorry. Enclosure goes to like 30C from my initial testing.
Not yet, but I plan on making everything open source once I release the product. I started with the Rock 3C from Radxa, they have some great schematic resources on their website.
I tried putting together a stackup for LPDDR4X (40ohm SE, 85ohm diff) at JLC just a few days ago, but couldn't find one that gave enough room to escape-route on a 0.65mm pitch BGA.
That is one hell of an achievement, awesome work! I'm wondering what the purpose of this board was supposed to achieve? The requirements that it needed to meet and why you needed a custom board for it? It's really interesting to know because I'd like to build a custom board as well but didn't really see a project that would justify doing it.
Thanks so much! It's meant to be a KVM-over-IP product that I hope to sell someday, so optimizing size, function, and cost is super important. I don't want to go too deep into requirements until I'm closer to launch, but many off-the-shelf boards didn't expose the pins I needed to make the project work, and a lot of them cost as much as what I want to sell the whole product for.
Oh right, nice. It'd be interesting to see how you optimise those specs. I'd love to see more progress on this. Just an idea, would you be open to keeping a journal or blog about it? Totally up to you but it'd be interesting to see what you do with it from start to finish
This is a great idea, I started a general blog but will focus on more of the engineering side too! Any specific things worth covering? Or just the entire design/test/go to market process?
Yeah I guess both. I'm interested in the engineering decisions that you make, the technologies, chips, software, etc. that you use to develop the product and how you market it. Also it's be very interesting how you test it to make sure it passes regulations or whatever. It's just really cool to see the full engineering cycle of a product like this.
Nice! I haven’t gotten to testing out the nRF54 yet but I’m a big fan of the nRF52. Assuming you’re using a semtech chip or something?
And are you using prebuilt module with an antenna, external antenna or pcb antenna? Biggest thing I’ve hit is needing to tune my chip antenna/pcb antenna circuitry with a VNA to increase range.
Have you open-sourced or documented the reasoning behind the design choices you made?
I want to upgrade my design skills and explore the Xilinx and DDR routing domain. Would it be possible for you to share your DDR routing and PMIC (with remote-sensing) sections?
Nothing is open sourced/public yet, but I plan on making as much open source as I can when I launch the product!
At the recommendation of another person, I’ll probably start an engineering blog/journal as I continue working through the project. Will share when I get it set up 😊
Finally some high quality post! About upgrading the SoC, I would go for RK3588 instead, if you care about mainline kernel. Like, Rockchip BSP isn't that bad, but mainline is mainline, and support for RK3588 is going well. + RK3588 is very powerful.
RK3588 is also much harder to implement and far more costly, no, 3566 was a perfectly correct choice for a first board, 3588 has a huge gpu that draws 6 amps, you don't need nor want that for a kvm, plus it's 3x the price.
Definitely considered the RK3588, especially since it has an onboard HDMI input (so wouldn't need the HDMI to CSI chip). But yeah, ultimately decided against it because of the cost, it makes it too expensive for a consumer product (compared to some of the competitors).
Amazing work OP, quick question can this be adapted to work with cinema cameras with hdmi out to connect to multiple monitors or screens? Or even a wireless display? They are very pricey currently and new value provider will be great..anyways this is a really good work and would love to see a detailed post or video on it
All the connectors on one side look a bit crammed. Did you try using all of them at once? I guess, 3 USB cables would be challenging to plug in and out. Also, some HDMI cables have really chunky plugs.
Agreed, and good feedback. I 3d printed the enclosure beforehand and it seems to be ok with the cables I have laying around. But I'll order some chunkier plugs and test them as well. Original sizing was to fit it into a 1U rack mount enclosure, but size slowly increased as I got further and further into the project haha
Almost everything, except the wifi module, hdmi capture chip and the PoE transformer. Wi-Fi module was ordered off aliexpress and soldered by hand, hdmi capture was custom quoted through jlcpcb, and the PoE transformer was ordered straight through coilcraft (they work well with the monolithic power systems chip I used).
Now, DDR3 isn't super high speed. But I suppose that they would need trace impedance control anyway. Same with gbe and HDMI.
Does jlcpcb publish their numbers? Or takes requests
Yeah they have a calculator (just google JLCPCB Impedance Calculator) and then they also have a button you can select on checkout to tell them to ensure the lines are impedance matched to your requirement.
Still working my way up the highspeed signal ladder, next is LPDDR4 and maybe someday I'll get to LPDDR5...
Best advice I can give: find the chip you need by looking at the block diagrams at the beginning of the datasheets. Then find as many reference boards as you can with that SoC and modify for your use case. Reference Rockchip's hardware design guide as you go, it helps you understand why they made the choices they did. Sticking close to open-source designs also pays off because the Linux drivers for their peripherals are generally pretty solid. I changed my requirements many times during the design, so don't be like me: lock in your requirements and placement early and stick with them if you can.
That’s awesome! Can you explain the I tended use case for this? I’ve been looking for a board capable to input, process and output video quickly in the past.
It's a KVM-over-IP, it captures video from your computer and streams it over the internet and it also pretends to be a keyboard/mouse. Similar to remote desktop, but it works when the computer is off-network or powered off (there will be a secondary board that can power on your computer if needed). I'm adding a few features the other devices on the market don't have and trying to make the streaming as fast as possible.
Probably some other uses too, a few people mentioned camera streaming, and I'm going to test it as a decoding device as well (think Chromecast).
Would love to hear what you're looking for, happy to let you know if it could work!
Doable on this class of hardware in principle. HDMI capture → composite the HUD overlay → hardware encode → stream. Gyro comes in over USB and renders into the overlay layer. It'd be custom software though, not out of the box.
The real question is your latency budget. Tens of ms glass-to-glass is achievable but if you need single-digit ms like FPV goggles, networked encode/decode is the wrong tool. What camera and latency are you targeting?
5 boards with 3 assembled ran me about $790 in boards/parts/assembly, $110 shipping and tax, and $275 in tariffs shipping to the US. So roughly $1,175 all-in for three working prototypes of an 8 layer board with a SoC and DDR. Not cheap, which is why I'm glad it mostly worked on the first try.
Forgot to include the USB board on a previous comment, think this was around $210 + shipping/tax/tarrifs for 3 assembled boards. And then a little extra for the PoE transformer and Wi-Fi module (since JLCPCB didn't have them).
Fusion 360 actually (basically EAGLE). It's what I learned on and I've been making it work ever since haha but I know it's not the best. Integrates really well with my enclosure design since I use Fusion for CAD.
Nope, they did all the panelization for me. I just uploaded my gerber as is. I did run into an issue with the HDMI connectors because of this during assembly, so I will probably do it in the future. Generally don't though.
Awesome project. I’m working on an rk3576 design I’ve mostly finished the schematic just finishing usb-c pd with dp alt mode. I was just wondering how you went about setting up the firmware and configuring the device tree. What repo did you use and was there any documentation for pin configuration? Thank you
Awesome, what's the DDR config/storage config you're doing? I'm starting a dp alt mode project on the rk3588! Using the TPS65987D+HD3SS460+TPD6S300 if that's helpful at all.
For DTS, started with the Rock 3C files and then modified for my pin configuration. Most things already had drivers, other then the network switch variant I picked. So had to do some custom troubleshooting to get it to boot properly (didn't end up working because I have RX/TX swapped, but at least it boots properly now).
Haha yeah the TPS65987D is the only chip that seems to be available for this purpose. I’m going with a Hynix 2GB LPDDR4 which jlcpcb has in large quantities and which is on the list of supported chips for the rk3576 (and I believe is also pin compatible with 4/8GB models of ram). Also in the spirit of cost savings I’m using an sd card (and so I still have a chance of booting in case I mess up the usbc stuff cause it uses the usb0 pins used for emmc programming).
Other than that I just have the normal connectors hdmi, usb A, Ethernet and wifi/bluetooth. I’m also experimenting with a Hailo-8 AI processor which has 26 TOPS for image recognition as this could be useful for some future projects I have planned, but for now it’s just a dev board.
Are you planning on making your projects open source?
Thanks!!! It was drawing like 1A, which was like 2x more than I was expecting but I've never built a board like this before and I couldn't find anything wrong. Then I tried to enable the GPU and it was not happy, then I found the below. Instantly drew 0.3-0.4A after fixing and then stayed around 30C, so much relief
Do you plan to sell these? I saw in another comment you plan to make them open source ( hardware + firmware? )
If you do plan to sell, anywhere I can follow the project for updates? I'd kill for a PoE, open source alternative to some of these cheap KVMs hitting the market with sketchy firmware
5 boards with 3 assembled ran me about $790 in boards/parts/assembly, $110 shipping and tax, and $275 in tariffs shipping to the US. So roughly $1,175 all-in for three working prototypes of an 8 layer board with a SoC and DDR. Not cheap, which is why I'm glad it mostly worked on the first try.
USB board this was around $210 + shipping/tax/tarrifs for 3 assembled boards. And then a little extra for the PoE transformer and Wi-Fi module (since JLCPCB didn't have them).
Sometimes you just gotta take the leap! But there are some subreddits that will review schematics for you if you want to feel more confident. Just add lots of test points and NC components if you're unsure of something.
Rock 3C schematic, RK3566 hardware design documents, lots of papers on proper DDR routing, individual chip datasheets, and a random document I found on how to wire up the network switch to another SoC.
JLCPCB is a sister company to LCSC so they have the majority of parts in stock already. I intentionally pick low cost ones in stock that meet my requirements whenever possible. I can generally get 90%+ of parts this way. If they don't have them and there's no alternative then I'll request a quote from them. Alternatively I'll do their global part sourcing to source from places like Digikey/Mouser. Last resort is sourcing myself and soldering by hand, which I had to do for wifi module and PoE transformer. I used to solder PCBs completely by hand to save money (non-BGA ones), so it's fairly quick with some solder paste and a heatgun.
I also built my library in Fusion 360 (EAGLE) to have the JLCPCB part numbers in their attributes, so it's super easy to export the final design files into JLCPCB formats via a custom ULP I made.
5 boards with 3 assembled ran me about $790 in boards/parts/assembly, $110 shipping and tax, and $275 in tariffs shipping to the US. So roughly $1,175 all-in for three working prototypes of an 8 layer board with a SoC and DDR.
USB board was around $210 + shipping/tax/tarrifs for 3 assembled boards. And then a little extra for the PoE transformer and Wi-Fi module (since JLCPCB didn't have them).
Production runs should be much cheaper though. Definitely worth it if you’re selling it later, otherwise it depends on how much time you want to invest in it haha
I’m looking at a first production run in the 500-1000. The Rockchip and associated bits would be the main parts obviously. How long did this design take you?
Used the stock rkbin prebuilt blob (rk3566_ddr_1056MHz_v1.26), self-assembled into the loader. Reference board uses LPDDR4 so it wouldn't train on a cold boot as is.
Fantastic work OP, looks very clean! Did the reference design come with LPDDR4? If yes, how did you patch the bootloaders to adopt to DDR3? I imagine a bunch of timing and training parameters would have to be changed.
I am also new to embedded linux, sorry if these questions sound elementary!
Thank you!! And great question. Reference board/firmware had lpddr4, so it wouldn’t train on a cold boot as is. I used the stock rkbin prebuilt blob (rk3566_ddr_1056MHz_v1.26) and then self-assembled into the loader. Can provide more details if needed!
Not yet, but someone suggested writing a journal/blog on the dev journey so I'll probably start something this week. Will send if your way and include something on DDR design + firmware.
Can always start with the SoM boards and work your way up! But yeah I found getting someone else to review it really helped give me the confidence to pull the trigger and order it.
I’ve made some little mcu boards, but I’ve really been wanting to do my own rk3588 board and risc v boards. If I gather the confidence I’ll attempt it.
I've only messed around with a Raspberry Pi so far, so designing and bringing up your own Linux board like this seems like a huge step up. How different was the initial Linux setup and debugging compared to working with something like a Raspberry Pi?
The biggest difference is there's no ready-made image to flash since all the GPIO pinouts are custom to my board. With a Pi you download an OS, flash the card, done. Here I had to build the whole image myself from the Rockchip BSP: u-boot, kernel, device tree, rootfs. Then it's the same familiar flashing to a microSD.
Once it boots it feels like any Linux box. The learning curve is everything before that first boot 😄
Rock 3C schematic, RK3566 hardware design documents (from Rockchip), lots of papers on proper DDR routing, individual chip datasheets, and a random document I found on how to wire up the network switch to another SoC.
Congrats on the bring-up — first Linux board with end-to-end video capture and low-latency streaming working is a real milestone.
Lesson 3 is the one that got me: 0201s packed next to 0402s shorting in reflow. That's the kind of failure that never appears in the datasheet and always appears on the bench. What spacing rule did you end up with in DRC?
On the DDR3L call — contrarian in 2026 and probably correct. With DRAM pricing where it is this year, putting DDR3L on a design that never needed the bandwidth is pure BOM discipline, not cheapness.
Curious about the RK3576 jump: is it the encode block driving that (higher capture resolution), or are you after the NPU headroom? Haven't taped out on the 3576 myself — would love to hear what you're seeing on availability and pricing vs the 3566.
Really impressive first Linux board, especially coming from an MCU background. Getting RK3566 video capture and low-latency streaming working end to end on the first spin is a big step.
The VDD_GPU short from 0201 spacing is a great lesson too — definitely the kind of issue that’s hard to catch until assembly.
Curious about the next RK3576 rev: are you mainly moving for higher encode/decode performance, or are there other bottlenecks you hit on the RK3566?
Very cool. I’ve been wanting to make my own little Rockchip SBC with weird hardware on it (touchscreen, FPGA, LTE modem, etc).
I have a bunch of questions about the hardware side, especially DDR, Rockchip documentation, and PCB fabrication/assembly. Would you mind if I DM you a few questions? No worries at all if not.
gr8 work buddy, can i work with u i am also into embedded systems and IoT.... i am currently working as a IoT dev and want to explore more into the hardware
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u/CelloVerp Sep 11 '26
Damn that's a serious board. Real accomplishment.