Interview with James Adams

Compute Module

We talk with James Adams about the new Raspberry Pi Compute Module.

On April 7, the Raspberry Pi Foundation announced an exciting new product. The Raspberry Pi Compute Module brings the Pi to a new professional audience – and it might even offer some new hacking opportunities for amateur Rasp Pi users. We asked Raspberry Pi's "Director of Hardware, Demon Welder, and Brewer of Beer" James Adams why the Compute Module is important and what it means for the open hardware community.

Raspberry Pi Geek: The Compute Module sounds like an exciting development for the Raspberry Pi community. Could you describe what it is and how it's different from an ordinary Pi?

James Adams: Basically, the Compute Module is the guts of a Raspberry Pi (the BCM2835 processor and RAM) plus 4GB of Flash on a small 67.6x30mm circuit board that fits into a standard DDR2 SODIMM socket (note the pinout is completely different from that used for actual DDR2 SODIMM modules!).

Apart from the interface to the Flash chip, all other interfaces are brought out to the module pins and are available for general use. So, you get a load more GPIO, two serial camera interfaces to the Pi's single one, and two display interfaces, again with the Pi only having a single one. You also get pins for HDMI, USB, and composite TV out just like the Pi.

Of course, the module is useless by itself, it needs to be plugged into a board that will provide the necessary power supplies and wire up the interfaces as required for the application. That is the real difference from the Pi – you'll need to do a bit of work and spin a board; however, there is complete flexibility in both the available interfaces and end form factor. We've done the difficult bit of routing out the fine-pitch BGA processor, memory, and Flash on the module itself, so a carrier PCB will only need to be relatively simple for most applications.

We are also making a simple "IO Board" available that powers the module and provides USB and HDMI and just breaks the remaining interfaces out to pin headers for easy hacking – but this is more of a get-started board and reference design; we expect most users to spin their own board.

RPG : Is it fair to say the Compute Module is targeted toward professional users  – circuit designers and embedded systems specialists?

JA : The problem we're trying to solve with the Compute Module is one of availability. Unless you are going to buy a very large number of BCM2835 (Pi processor) and memory and Flash chips, you either won't be able to get hold of the devices at all (this is particularly true of BCM2835), or you will end up paying quite a premium for them. When I say large numbers, I mean getting up into the hundreds of thousands type range. We are leveraging our ability to buy these devices at sensible prices and we're packaging them up into an easy-to-use form factor at a very low price. So, if you only want to make 100 or 1,000 products, you can still get the same low price as the guy building tens of thousands.

We are hoping by putting this kind of technology (which was not really available before) into people's hands cheaply, we will help drive innovation. Now the "man in a shed" or small company can buy the same low-cost mobile tech that a few years ago only the big guns (think Nokia, etc.) could. That's exciting and disruptive, and it's exactly the kind of thing we like to do. We are really looking forward to seeing what people use the Compute Module for.

Going back to the question, we do see the majority of these going into commercial products; however, I'm more excited to see how the module is used by hackers and makers and "the little guy" to bootstrap new products and businesses. We expect to see a few Kickstarter projects based around the Compute Module for sure.

RPG: What's an example of something one would do with the Compute Module in the real world? Describe a scenario where this new tool would be useful.

JA: I think there are so many possibilities it's difficult to choose! The Raspberry Pi (and hence Compute Module) is a cheap and low-power way to add network connectivity and compute horsepower to many types of product. Its Linux software stack is also actively developed and now very stable. We expect to see a lot of "Internet Of Things" type of applications. The other thing the BCM2835 does extremely well is video encode/decode and 3D graphics. We see this being useful in digital signage applications, video recording and imaging applications, and media players. A typical scenario would be where someone has used a Raspberry Pi as the core of a product, but the form factor is constrained or compromised by the form factor of the Pi. We have increasingly been seeing people do just this, and the Compute Module solves the problem.

RPG: Does the appearance of the Compute Module mark a new development for the Rasp Pi Foundation? Is the foundation evolving from an organization focused on education and the hobbyist to a group that is promoting open hardware through a broad range of different industry niches?

JA: The core focus of the Foundation is and always will be educating kids in computing, and the revenue stream generated by the Compute Module goes straight back into the Foundation to further these aims. Having said that, we are not trying to restrict learning to kids and the learning materials we generate can benefit everyone. We would not be here without our amazing community of hackers and makers – from the ones actively contributing to the software or ecosystem, down to the guy buying one Raspberry Pi. It all helps, and providing tools for these guys and industry where there is an obvious market need and that provides money for our charitable causes is a no brainer.

RPG: You previously mentioned the Compute Module IO Board. What is the IO Board and what will users do with it?

JA: The IO Board is designed to be both a simple reference design for the Compute Module, and a board that can be used to prototype a hardware project before going to the expense of making a custom PCB. The IO Board provides power to the module, has HDMI, USB, and flex connectors and pin headers for the two cameras, two displays, and GPIO, respectively. You can imagine it as a Raspberry Pi Model A with much more connectivity. While the IO Board is designed to be a prototyping platform and reference design, we can see it is also going to be useful for the hackers and makers who need to use the extra functionality of the Compute Module in projects. We'll be interested to see what the demand for this board is in the longer term.

RPG: Your blog post says the Compute Module provides, "many more GPIOs and interfaces" than an ordinary Rasp Pi. Is it possible a home hacker might find some enjoyment in playing with the Compute Module and IO Board together? Do they offer any capabilities you don't get with an ordinary Pi, or is this specifically a tool for circuit design?

JA: Most definitely. While we think that for the majority of users the Raspberry Pi will suffice (and will obviously be easier to use), there are certain things that can only be done on the Compute Module  – attaching two cameras for instance. If you really need large amounts of GPIO for some reason, you may want to us a Compute Module. We are expecting that fairly soon there will be many Compute Module carrier boards created by the community to address the various use cases and possibilities that the Compute Module opens up.

RPG: I'm guessing the Compute Module didn't just appear out of the blue – this is probably something you've been working on for a while. Do you have any teasers for what lies ahead? Any more interesting Raspberry Pi products in development now that will appear at a later release date?

JA: For the moment, we're working hard to get the Compute Module and IO Board into production and available in June. We're also developing an official Raspberry Pi display module that plugs into the Raspberry Pi (and IO Board) display interface(s). This is a high-quality 7-inch display with 10-point touch, and we're working hard to make sure it will be available at a sensible price. We're also working on software to enable the dual cameras and displays to work properly with Compute Module (we've had these working in the lab, but we need to do a bit of work to make it easy to use and integrate nicely into the current software stack).

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