Looking for less powerful and cheaper but open alternative to RPi Compute Module - Page 1
Forum section: electronics / general

author: midix
author_rank: Contributor
timestamp: April 18, 2015, 09:54:27 pm
content: Hi, EE experts!We are a small software company and we have an idea for a product which will need a hardware platform to run on.As we want our product to be open for maker/hacker community, I now would like to take the opportunity and talk to you out there.Unfortunately, I cannot yet disclose much details about the project (who knows, how it will go). It is related to audio streaming, but no heavy encoding/decoding, just raw PCM audio data.I'll try to highlight some important points which might be affected by our choice.At first we had an idea to use Raspberry Pi Compute module. Currently we are experimenting with Raspberry Pi B+ and it works fine, but it seems to be too powerful for our needs. We don't use its video core at all, and the CPU also is usually only loaded by 10-20. Also 4GB of eMMC flash means lots of unused space. Raspberry Pi Compute module is not the best for us - we'd be paying for unused resources.But there is one thing we really like about Raspberry Pi Compute module - it is openness. A product based on it would be available to enthusiasts. Even flashing RPi Compute is pretty safe - just connect to USB and write the firmware to eMMC flash memory. It seems almost impossible to brick this device.We'd like to find a cheaper, less powerful system-on-chip (SoC) or computer-on-module (COM) or just separate chips of CPU+RAM to use in our product, but we want to have the openness and almost fool-proof flashing of RPi. It would be fine to have some binary-only vendor specific drivers, if only the vendor would provide them to public or give us permission to distribute them at least in binary form (of course, open source would be the best, but let's be real - some SoC manufacturers want to keep some things secret).Our product will require the following interfaces to the outside world:- a WiFi b/g/n (with access point mode support) adapter- a Bluetooth 4 adapter- two Ethernet adapters in bridge configuration (ideally - two port hardware switch)And internally we'll need and SPI port with support in Linux kernel. Also it would be great to have UART port for serial console.Hardware float support will be needed for our custom software.We could just look for the chips with good support in Linux kernel for the embedded platform of our choice and then look for the prices and availability in the market. But there are some SoCs with some of this functionality built-in, thus it might turn out to be cheaper than to use separate components. Correct me if I'm wrong.Price is really important to us. The product won't be high-end device, so we'd like to keep the price low, but maybe having just a little bit of spare processing power for future possibilities.If there are cheaper production ready, stable and open alternatives to Raspberry Pi Compute module, I'd be really grateful for your experience and expertise.

author: amyk
author_rank: Super Contributor
timestamp: April 19, 2015, 01:04:41 am
content: Even more open than RPi... I don't know if this is enough processing power for you though:https://www.olimex.com/Products/SOM/A13/A13-SOM-256/https://www.olimex.com/Products/SOM/A13/A13-SOM-512/

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 19, 2015, 03:55:43 am
content: Allwinner is not very open source friendly. In fact, their practices are earning them the name "AllLoser".http://www.phoronix.com/scan.php?page=news_item&px=Allwinner-Stripped-Symbols

author: midix
author_rank: Contributor
timestamp: April 19, 2015, 10:50:34 am
content: Thank you for ideas. I looked at the options you mentioned.AR9331 at first seemed great option but unfortunately it has no hardware float support. We might need it for some custom software. It's my fault, I forgot mentioning it, I'll update the post.I also foundhttp://www.acmesystems.it/ariettaand they claim to have completely open Linux software. There's just one quirk - Arietta has microSD instead of flash memory.Is Atmel ARM platform really that open-source friendly? In that case we could use it on our custom designed platform with flash eMMC. But then production might turn out to cost the same as buying RPi Compute...I have seen a similar product to ours implemented on Freescale MPC8314E:http://www.mouser.com/ds/2/161/MPC8314EEC-51265.pdfbut I'm not sure how open Freescale is and how do they treat small startup companies - is it possible to buy their SoCs in quantities less than 1000?

author: tggzzz
author_rank: Super Contributor
timestamp: April 19, 2015, 11:39:22 am
content: XMOS multicore processors are explicitly designed for hard realtime systems, to the extent that the compiler will tell youexactlyhow many cycles each operation and loopwilltake. Try getting that crucial info for any other processor family!They are very cheap, available at DigiKey etc, and they have been successfully used directly in the audio stream of audio systems.

author: amyk
author_rank: Super Contributor
timestamp: April 19, 2015, 02:19:56 pm
content: Quote from: NiHaoMike on April 19, 2015, 03:55:43 amAt least they're better than Broadcom with respect to releasing datasheets...

author: midix
author_rank: Contributor
timestamp: April 19, 2015, 06:24:21 pm
content: We (and also Broadcom) are lucky having Raspberry Foundation. Without them, Broadcom wouldn't get such popularity. But who knows where we would be today, had Raspberry Foundation picked some other SoC...