Noob question on where to source capable SoC microcontrollers - Page 1
Forum section: electronics / general

author: UltraTrunks
author_rank: Contributor
timestamp: August 21, 2014, 07:33:21 pm
content: I'm new here so go easy on me. I've got an ambitious project to design and build my very own Linux board. Think of it as a lifetime capstone project.I've been poking around and learning a bit about sourcing parts. I've never really had a need for any components that I couldn't just get off Amazon before. So needless to say that I'm not a digikey or mouser power user.So I have Raspberry Pi, its really cool and I like it a lot. I'm inspired to tinker a bit and try making something of my own, just to learn and have fun. For example I was just curious on how much it would cost to purchase the processor that the Rpi is running. TheBroadcom BCM2835. I came up bupkis. Tried looking for the processor on the Beagle Bone as well. TheTexas Instruments OMAP3530. Not sure if the Beagle Bone's processor is really a SoC. I want a SoC component because I definitely don't want to be messing around with MCU's and the like. So little chips like this are perfect. But how the heck do you actually get one? I don't mind having a dev board for one at first. But at some point I'll need the raw chip. All the micro controllers on mouser and digikey don't even come close to SoC's like this. Most don't even have 1Mb of RAM. Now you can definitely get some distros of Linux to run on that little memory. But I want a fairly capable Linux install. So the 128/256/512 Mb range's are what I'm really looking for. But where do you actually buy one at? Where can I find embedded SoC components of this caliber for purchase?

author: bpye
author_rank: Contributor
timestamp: August 21, 2014, 07:39:21 pm
content: Freescale are one example of a manufacturer for which you can get the parts quite easily, looking at Farnell there is even an ARM9 part, i.MX23, that comes in an LQFP. These aren't quite single chip solutions though, no SoC really is. You are almost always going to need external RAM and flash, some oscillator and probably a fair bit more (I'm not experienced with SoC stuff).

author: andersm
author_rank: Super Contributor
timestamp: August 21, 2014, 07:47:48 pm
content: Broadcom will only sell direct to large OEMs, so no chance there. You can get most TI, Freescale, Atmel etc. parts via the usual distributors.The chips you are thinking of are designed to run from external storage and will either have no on-board RAM and flash, or only a small amount to help bootstrap the system. Renesas have some chip in their RZ line with 10MB of on-board RAM, and that is the largest chip I know of.No offense, but you are way out of your depth here. Since many of the boards are open source, download the design files of a few, and download and read the datasheets and manuals of an OMAP or i.MX chip to get some idea of what is involved.

author: FrankBuss
author_rank: Unknown
timestamp: August 21, 2014, 07:49:39 pm
content: You can get the OMAP3530 at Digikey, just search for it. Same for some Atmel parts, like the AT91SAM9 series chips, which can run Linux (with additional external RAM and flash). But I think all of these powerful chips are in BGA, so really difficult to create a board for it with impedance and length matched traces to the RAM and routing and connecting all the other hundreds of pins etc.What projects did you do so far? Maybe better to start with a simpler project first.

author: Maxlor
author_rank: Frequent Contributor
timestamp: August 21, 2014, 07:59:53 pm
content: You probably won't find the SoC that you seek. But you can buy the i.MX6 processors from Mouser and other distributors, as well as the RAM and flash that goes with it. Connect them, and you've essentially got what a SoC gives you, albeit at the cost of a bit more board space.

author: UltraTrunks
author_rank: Contributor
timestamp: August 21, 2014, 08:43:15 pm
content: Ok, well got some things cleared up.Quote from: andersm on August 21, 2014, 07:47:48 pmI kind of focused on the fact that I could not find this chip for sale. It was really puzzling to me. If someone wanted to buy a crate of Broadcom chips, I don't think Braodcom would mind. But if they only sell to their buddies, well then they only sell to their buddies. Good to know.Quote from: bpye on August 21, 2014, 07:39:21 pmNever even considered Freescale. They actually have a fab by my house. I always considered them a manufacturer and assumed they operated through resellers to hock their stuff. Also, never heard of Farnell. So that's a new place for me to look in the future. Thanks.Quote from: FrankBuss on August 21, 2014, 07:49:39 pmWhen I searched Digikey it seemed they were already attached to boards and such. And quite outrageously priced as well. Like $300+ per unit. Little strange. But yes, the powerful chips are BGA packaged and not something I intend to mess with. Ideally I'm looking for something in QFP package. I'm really just curious about the SoC chips. However, I would like to have a significant amount of ram. For storage, I'm ok with having off die since I intend to use micro SD for this anyways. However, having the RAM off chip I'd like to avoid. But looks like that may not be an option. As for my project, I'd like to simply build a board that can run linux at first. That'll be tough enough right there. But ultimately I'd like to build a flight controller board that is powered by Linux. There are other flight controller boards out there, but I'm a DIY kind of person and I want to learn some new things and have some fun doing it.Quote from: Maxlor on August 21, 2014, 07:59:53 pmProbably on the money.

author: nctnico
author_rank: Super Contributor
timestamp: August 21, 2014, 08:52:13 pm
content: For low volume there are only two choices: Freescale (iMX) or Texas Instruments (Omap or whatever they named it this month).Using chips from other manufacturers is just asking for a lot of trouble due to lack of (community) support and documentation.

author: UltraTrunks
author_rank: Contributor
timestamp: August 21, 2014, 09:18:07 pm
content: Quote from: nctnico on August 21, 2014, 08:52:13 pmI thought Broadcom was fairly popular, isn't it? I did some work with some open source router firmware back in the day. AndOpenWrt,DDWrt, andTomatoall had the best support on the routers that ran Broadcom chips IMO. This may be a special case though since routers are near and dear to a hackers heart and a community would spring up around the subject no matter who made the chips or how poorly documented it was.

author: nctnico
author_rank: Super Contributor
timestamp: August 21, 2014, 09:26:54 pm
content: Don't go the Broadcom route! Most use MIPS cores so a lot of software which depends on machine specific assembly language (Firefox for example) won't run on it. These machine may also be big endian which is another major PITA.

author: bpye
author_rank: Contributor
timestamp: August 21, 2014, 10:16:42 pm
content: Quote from: UltraTrunks on August 21, 2014, 09:18:07 pmAs you said it's pretty much a special case. Both Freescale and TI have a lot of documentation for their parts without having to sign an NDA, pretty much just excluding the graphics cores. Broadcomm's only "open" device is the processor used in the Raspberry Pi, everything else they have will require you to sign an NDA for any documentation I do believe.

author: FrankBuss
author_rank: Unknown
timestamp: August 21, 2014, 10:30:16 pm
content: Quote from: bpye on August 21, 2014, 10:16:42 pmNo, half a year ago the full documentation for the GPU was released:http://hackaday.com/2014/02/28/raspberry-pi-gpu-goes-open-source-10000-bounty-for-quake-3/

author: bpye
author_rank: Contributor
timestamp: August 21, 2014, 11:04:37 pm
content: Quote from: FrankBuss on August 21, 2014, 10:30:16 pmSorry, I meant to refer to the device in general, not just the CPU for it.

author: FrankBuss
author_rank: Unknown
timestamp: August 21, 2014, 11:17:32 pm
content: There is a datasheet for the peripherals of it:http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdfand the schematic for the Raspberry Pi is available, too, so I guess you could develop your own board with it. But right, you don't get the full datasheet unless you are a big company and sign a NDA, unlike for the other chips from TI, Freescale and Atmel. I guess Broadcom don't want to support small companies or individuals, because they think it is too expensive for them.

author: sacherjj
author_rank: Frequent Contributor
timestamp: August 22, 2014, 02:40:39 am
content: Quote from: nctnico on August 21, 2014, 08:52:13 pmFor low volumes, these are the two I would pick. For larger volume, they are not price competitive with other SoC's in price vs processing power. If you go with any of the Chinese SoC's, you can get really good price. However, if you do not want to do board assembly in China, you are out of luck. It is almost impossible to export just the processor. We went forward with a design, only to learn this late in the game.We are using the Embedded Atom platform, which is a little harder to get into that TI or Freescale, but price per performance is better. However, the complexity of having BIOS and a few other factors make it not recommended for ease of design. It is another layer of firmware to get right.

author: andersm
author_rank: Super Contributor
timestamp: August 22, 2014, 05:30:06 am
content: Quote from: UltraTrunks on August 21, 2014, 08:43:15 pmYoucan't have searchedtoo hard. Dev kits from the processor manufacturer are often very expensive, you can usually find comparable boards from other manufacturers, like the CubieBoard for i.MX6 and so on.QuoteThen you will likely have to go for older, ARM9-based chips. The more modern chips are 400+ pin parts, which just isn't feasible as QFP.Here's one exampleof a DIY Linux board.

author: bpye
author_rank: Contributor
timestamp: August 22, 2014, 03:09:42 pm
content: I actually did some looking around and Freescale offer a Cortex A5 in a 176 pin QFP, the VF3xx series.

author: diyaudio
author_rank: Frequent Contributor
timestamp: August 22, 2014, 04:40:12 pm
content: Quote from: UltraTrunks on August 21, 2014, 07:33:21 pmWhy not start with the beagle-bone, its open and you have community support. I don't think someone with zero experience will achieve a successful working boot-able board with zero experience.You might want look at fedevel if you want to build a working i.mx6 board from zero and see for yourself what it takes.http://www.imx6rex.com/

author: miguelvp
author_rank: Super Contributor
timestamp: August 22, 2014, 05:36:27 pm
content: I have my eye on this:https://developer.nvidia.com/jetson-tk1Nvidia has been catering to the development community quite a bit lately, but I don't think you can just purchase the chip and build your own board.The K1 is a pretty powerful SoC with 192 CUDA cores with unified architecture, so it can also do OpenCL.I've haven't played with L4T (Linux for Tegra) for a couple of years so I don't know at what state they are, but I think the kernel source is all there. The only thing they didn't have was source for the actual GPU device driver so you can't customize that.But the features are quite impressive just for $200

author: UltraTrunks
author_rank: Contributor
timestamp: August 22, 2014, 08:51:55 pm
content: Quote from: andersm on August 22, 2014, 05:30:06 amWow, this is a really great link. Very impressive. I'm sure I'd have some questions for this guy down the road. Hopefully he'll be responsive on his GitHub account.Quote from: diyaudio on August 22, 2014, 04:40:12 pmWell my ultimate goal is design my own hardware. That's where most of the learning curve is going to be for me. Getting premade boards really isn't going to help me push the envelope in the direction I want.

author: nctnico
author_rank: Super Contributor
timestamp: August 22, 2014, 08:58:46 pm
content: You can make your life a lot easier if you don't try to make a very compact board. The module from the link is pretty crammed with components. If size isn't a major issue you can use a 6 layer board with components on one side only.

author: miguelvp
author_rank: Super Contributor
timestamp: August 22, 2014, 11:12:47 pm
content: Not ARM but x86 Intel Quark SoC is available for under $20 quantity 1.http://www.mouser.com/new/Intel/intel-quark-x1000/Altera has also FPGAs with embedded dual core A-9 SoC processors, haven't looked at the prices though.http://www.altera.com/devices/fpga/cyclone-v-fpgas/hard-processor-system/cyv-soc-hps.htmlHmm, around $110 for onehttp://www.mouser.com/ProductDetail/Altera-Corporation/5CSEBA5U19C8N/?qs=sGAEpiMZZMvoScKlWpK8TM8u6IoJsKfqzm10f%252bBt16g%3d