Arduino: now a Single Board Computer!

I like the term "bare metal microcontroller" to denote the processors on Arduino AVR and ARM Cortex-M class boards.  These contrast strongly with those boards which are based on "application processors" that have an MMU and therefore run full operating systems (mostly Linux) and so their applications execute as user-mode processes in virtual memory --- definitely not "bare metal".

It provides a clear distinction and so keeps discussions from attempting to compare apples with orangutans.

PS. It's appalling to see makezine.com make this elementary error though.

PPS.  The source of the error seems to be Intel themselves!

Intel writes (in the FAQ):

 

Q: Can I run Linux on Intel Galileo?

 

A: Yes. Intel Galileo runs Linux* out of the box. It comes in two flavors; the default is a small Linux. If you add an SD card to your kit, you can add a more fully-featured Linux. Refer to the Intel Galileo Getting Started Guide and Intel Quark SoC X1000 IoT Development Kit Software GSG.

I'm still figuring out exactly what this means, but at best it's going to be something like the old uClinux, which was pretty horrible at best.  After all there is no MMU in Quark to support the normal Linux kernel --- see the Quark datasheet.  (uClinux is effectively EOL now owing to MMUs having become so ubiquitous.)

PPPS.  The Galileo Getting Started Guide refers only to Linux support on the host side, not on the board.

PPPPS. Oh dear.  If you zoom into the image showing what they load from uSD card, it boots into:

Poky 9.0 (Yocto Project 1.4 Reference Distro) 1.4.1 clanton /dev/ttyS1

I've got a very bad feeling about this.  I thought the days of MMU-less "Linux" derivatives were over.

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IMPORTANT ADDENDUM:  Quark does have an MMU, it's just not mentioned in the SoC Datasheet.  See this post.

Intel writes (in the FAQ):

 

Q: Can I run Linux on Intel Galileo?

 

A: Yes. Intel Galileo runs Linux* out of the box. It comes in two flavors; the default is a small Linux. If you add an SD card to your kit, you can add a more fully-featured Linux. Refer to the Intel Galileo Getting Started Guide and Intel Quark SoC X1000 IoT Development Kit Software GSG.

Does this imply that your choices for boot device are either onboard or SD card, but not USB or network?

coder27 wrote:

 

Intel writes (in the FAQ):

 

Q: Can I run Linux on Intel Galileo?

 

A: Yes. Intel Galileo runs Linux* out of the box. It comes in two flavors; the default is a small Linux. If you add an SD card to your kit, you can add a more fully-featured Linux. Refer to the Intel Galileo Getting Started Guide and Intel Quark SoC X1000 IoT Development Kit Software GSG.

Does this imply that your choices for boot device are either onboard or SD card, but not USB or network?

Curious, isn't it?  Their very odd phrasing "a small Linux" and "a more fully-featured Linux" without mentioning any names of standard distros was one of the reasons that suggested to me (or at least didn't contradict) that this was uClinux running on a microcontroller --- this is not the case, as we now know.  But why the reticence to state the name of the distro in the FAQ?  There's nothing shameful in running Yocto.

It seems unlikely that Intel would have built in such a severe restriction on boot sources at hardware level, so perhaps this is a temporary limitation while they sort out drivers.  The mini-PCIe connector is a likely candidate for disk interfaces in the future, but Intel's brief 13-page Galileo Datasheet (more like a set of slides) suggests that mini-PCIe support is currently limited to "the WiFi library".

I think the latter term refers to support within Arduino sketches  though.  In plain Linux you might be able to do everything that Linux can do, driver support allowing.

but Intel's brief 13-page Galileo Datasheet (more like a set of slides) suggests that mini-PCIe support is currently limited to "the WiFi library".

I saw mention in one of the docs (I would have to hunt for it again) that the mini-PCIe

could be used for an additional host USB port, among other things like cellular network.

Morgaine Dinova wrote:

 

Curious, isn't it?  Their very odd phrasing "a small Linux" and "a more fully-featured Linux"

That could simply be the difference between Debian and something where 99% of stuff is provided by busybox. Depending on what else is in there, the 8MByte of SPI flash would be enough for a linux install, albeit nothing resembling what you'd find on a desktop install.

It seems unlikely that Intel would have built in such a severe restriction on boot sources at hardware level,

Depends. Seems more likely to be a firmware limitation. For example, the Minnow has very limited firmware, nothing like what you'd commonly find on x86 desktop/server boards.

Also consider the target market. Can RPi, BBB, etc. boot from network or USB ?  Do other Arduino boards ?   For something that's supposedly going to be around $60 you have to think that a lot of the complex (and therefore expensive) x86 baggage needs to get left out.

coder27 wrote:

 

but Intel's brief 13-page Galileo Datasheet (more like a set of slides) suggests that mini-PCIe support is currently limited to "the WiFi library".

I saw mention in one of the docs (I would have to hunt for it again) that the mini-PCIe

could be used for an additional host USB port, among other things like cellular network.

Part of the spec for miniPCIe is that it has a usb port wired to the connector as well as stuff like led and sim card connections. In some circumstances various parts are optional and I've seen at least one board that only provides usb to the connector.

There seems to have been some thought put into the miniPCIe physical connector to allow it to be used for a wide range of purposes, traditional wifi, cellular modem with remote SIM, usb bluetooth, all in the same form factor, possibly on separate cards, or even combined onto one.

One of my first thoughts from the wording was that the connector on the Galileo would be a usb only version and therefore limited in scope. However there's a block diagram in one of the docs that shows both PCIe x1 and USB2.0 going to the connector.

selsinork wrote:

 

Can RPi, BBB, etc. boot from network or USB ?

Pi can't boot from network or USB because booting is done by the utterly closed VideoCore.  However, BBB can boot from anywhere, in principle, since U-boot runs on the ARM which is free to configure any devices it wants prior to finding and loading a kernel.  And the 2GB flash means that U-boot always has somewhere to run and keep its configs while sorting out from where to get a kernel.

This doesn't mean it's easy if the boot support that one wants doesn't exist yet, but in the open source community that tends to get rectified pretty quick.

Ultimately though, anything can boot from anywhere (with the exception of secure boot systems), since whatever it is that loads the Linux kernel can load a generic boot loader instead.  Even poor ol' Pi has that possibility.

selsinork wrote:

 

Can RPi, BBB, etc. boot from network or USB ?

Pi can't boot from network or USB because booting is done by the utterly closed VideoCore.  However, BBB can boot from anywhere, in principle, since U-boot runs on the ARM which is free to configure any devices it wants prior to finding and loading a kernel.  And the 2GB flash means that U-boot always has somewhere to run and keep its configs while sorting out from where to get a kernel.

This doesn't mean it's easy if the boot support that one wants doesn't exist yet, but in the open source community that tends to get rectified pretty quick.

Ultimately though, anything can boot from anywhere (with the exception of secure boot systems), since whatever it is that loads the Linux kernel can load a generic boot loader instead.  Even poor ol' Pi has that possibility.

Morgaine Dinova wrote:

 

Pi can't boot from network or USB because booting is done by the utterly closed VideoCore.  However, BBB can boot from anywhere, in principle, since U-boot runs on the ARM which is free to configure any devices it wants prior to finding and loading a kernel.

http://elinux.org/RPi_U-Boot

So let me rephrase the question, where can the BBB, SL, Cubieboard, RPi etc boot from without loading u-boot first?   Generally I find they're all pretty limited, mostly to something out of SPI or NAND flash, or a FAT partition on SD card.

Ultimately though, anything can boot from anywhere (with the exception of secure boot systems), since whatever it is that loads the Linux kernel can load a generic boot loader instead.  Even poor ol' Pi has that possibility.

Precisely, so if Galileo has the possibility to boot u-boot (or similar) from SPI then it's exactly as capable as any other embedded device using u-boot.