Embedded computer architecture - Page 1
Forum section: electronics / beginners

author: mcdesca
author_rank: Contributor
timestamp: April 24, 2016, 01:02:33 pm
content: Dear everybody,I've been playing with several architectures on embedded systems (autonomous vehicles) from atmega's to pc104 boards. The requierements are always more or less the same: a computers running linux does the high level awareness and actuation decisions and a small micro (normally cortex-m3/m4) doing some real-time stuff.I have found these nice modules from Toradex which are relative powerful and cheap. I am planning to test the iMX7https://www.toradex.com/computer-on-modules/colibri-arm-family/nxp-freescale-imx7.I do not think the pc104 form factor is feasible anymore having these small computer on module boards.What do you think? What is your experiencie and recommendations?Thanks a lot.Best,

author: stmdude
author_rank: Frequent Contributor
timestamp: April 24, 2016, 01:16:24 pm
content: I was about to recommend a SoM, but it seems you've already found one.I've been using this:https://www.itead.cc/itead-core-aw204x.htmlwith pretty much no issues. Supported by the mainline kernel as well. Getting the GPU going without resorting to running Android on it is difficult at best though, but I assume that the same goes i.MX ones.If you want to go high-end, check out the Xilinx Zynq FPGAs. They have fast ARM-cores on-board that you can run Linux on. They're blazing fast chips, and since they're surrounded by programmable gates, you can get them to do (and interface with) pretty much anything.They're not cheap chips though.. They're available as SoMs as well.The only thing I'd be (a little) bit worried about when using SO-DIMMs in vehicular applications would be vibration. I'm not sure how well they deal with it. Then again, they're used in millions of laptops, so some vibration has to be okay.When you're designing the breakout board for the SoM (where the MCU goes, etc), don't over-complicate it (like I did). You're running Linux, so make your life easy if you're only prototyping. What does that mean? Well, use the USB controllers.. Need Ethernet? Plug in a dongle. Need WiFi? Plug in a dongle. Need BT? Plug in a dongle. Etc. Drivers for the dongles are (usually) already in the kernel.

author: Laertes
author_rank: Regular Contributor
timestamp: April 25, 2016, 12:19:30 am
content: I also find that high powered SoCs like the Zynq or the Cyclone V SoCs are great for embedded linux applications, it just gives you lots of freedom during prototyping(though it can be more work than processors). But for a smart vehicle, I imagine the extra real-time capabilities of programmable FPGA fabric could be very useful as well. You might even get away without an extra real time processor if your tasks are simple enough.SoMs I have made some mixed experiences with, they are easy to use, but they can also be cumbersome in environments that are thermally or mechanically demanding. These days, I mostly prototype on dedicated prototyping platforms like this one:http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&No=836- they are resonably cheap, somewhat compact and fully featured, plus you can mount a heatsink on the SoC. Potentially, you can just use this board with a daughter card with your realtime processor in your final device. Otherwise, you have some refrence schematics, PCB layout and a working BSP that you can base your own board on, so you can have pretty good chances of getting it right the first time, with all the advantages of a fully custom board.

author: uncle_bob
author_rank: Unknown
timestamp: April 25, 2016, 12:55:08 am
content: HiIf you look at a modern "not yet smart" vehicle, it can easily have a hundred processors in the vicinity of the driver's seat. I find that an amazing number, but it is indeed correct. A modern vehicle is already a distributed network of cpu's. Each one is targeted at a specific task and optimized to do that task. The days of doing an entire vehicle with a single CPU (no matter how powerful) are long gone.Bob

author: Kohanbash
author_rank: Regular Contributor
timestamp: April 25, 2016, 02:44:23 pm
content: PC-104 is good when you need lots of different type of IO. You can get all sorts of boards that fit in your stack.The downside is all the "spaghetti wiring" that tends to come out of all sides of the stack.

author: mcdesca
author_rank: Contributor
timestamp: April 25, 2016, 06:43:06 pm
content: It is just me or they are hard to buy? I've tried contacting the major vendors that appear as the first search results with no luck. I cannot directly place an order except for the itead A20 one. I'll keep trying, I'd like to try to avoid having to design the pcb myself.Thanks for the suggestions.

author: Kilrah
author_rank: Unknown
timestamp: April 25, 2016, 06:55:47 pm
content: This may interest you:http://shop.udoo.org/usa/neo.html?___from_store=other&popup=noOr their more powerful and larger variants with physically separate application and realtime processors.