We love seeing how quickly our community of makers responds when we drop a new product, and one of the fastest off the starting block when we released the new Raspberry Pi Compute Module 4 last week was YouTuber Jeff Geerling.
Jeff Geerling
We made him keep it a secret until launch day after we snuck one to him early so we could see what one of YouTube’s chief advocates for our Compute Module line thought of our newest baby.
So how does our newest board compare to its predecessor, Compute Module 3+? In Jeff’s first video (above) he reviews some of Compute Module 4’s new features, and he has gone into tons more detail in this blog post.
Jeff also took to live stream for a Q&A (above) covering some of the most asked questions about Compute Module 4, and sharing some more features he missed in his initial review video.
Raspberry Pi Compute Module 4 designer Dominic Plunkett was kind enough to let us sit him down for a talk with Eben, before writing up his experience of bringing our latest board to life for today’s blog post. Enjoy.
When I joined Raspberry Pi, James, Eben and Gordon already had some ideas on the features they would like to see on the new Compute Module 4, and it was down to me to take these ideas and turn them into a product. Many people think design is a nice linear process: ideas, schematics, PCB, and then final product. In the real world the design process isn’t like this, and to get the best designs I often try something and iterate around the design loop to get the best possible solution within the constraints.
Form factor change
Previous Compute Modules were all in a 200-pin SODIMM form factor, but two important considerations pushed us to think about moving to a different form factor: the need to expose useful interfaces of the BCM2711 that are not present in earlier SoCs, and the desire to add extra components, which meant we needed to route tracks differently to make space on the PCB for the additional parts.
Breaking out BCM2711’s high-speed interfaces
We knew we wanted to get the extra features of the BCM2711 out to the connector so that users could make use of them in their products. High-speed interfaces like PCIe and HDMI are so fast coming out of the BCM2711 that they need special IO pins that can’t also support GPIO: if we were to change the functionality of a GPIO pin to one of the new high-speed signals, this would break backwards compatibility.
We could consider adding some sort of multiplexer to swap between old and new functionality, but this would cost space on the PCB, as well as reducing the integrity of the fast signals. This consideration alone drives the design to a new pinout. We could have tried to use one of the SODIMM connectors with extra pins; while this would give a board with similar dimensions to the existing Compute Modules, it too would break compatibility.
Compute Module 4 mounted on the IO Board
PCB space for additional components
We also wanted to add extra items to the PCB, so PCB space to put the additional parts was an important consideration. If you look carefully at a Compute Module 3 you can see a lot of tracks carrying signals from one side of the SoC to the pins on the edge connector. These tracks take up valuable PCB space, preventing components being fitted there. We could add extra PCB layers to move these tracks from an outer layer to an inner layer, but these extra layers add to the cost of the product.
This was one of the main drivers in changing to having two connectors on different edges of the board: doing so saves having to route tracks all the way across the PCB. So we arrived at a design that incorporated a rough split of which signals were going to end up on each of the connectors. The exact order of the signals wasn’t yet defined.
Trial PCB layouts
We experimented with trial PCB layouts for the Compute Module 4 and the CM4 IO Board to see how easy it would be to route the signals; even at this stage, the final size of the CM4 hadn’t been fixed. Over time, and after juggling parts around the PCB, I came to a sensible compromise. There were lots of things to consider, including the fact that the taller components had to go on the top side of the PCB.
The pinout was constantly being adjusted to an ordering that was a good compromise for both the CM4 and the IO Board. The IO Board layout was a really important consideration: after we made the first prototype boards, we decided to change the pinout slightly to make PCB layout on the IO Board even easier for the end user.
When the prototype Compute Module 4 IO Boards arrived back from manufacture, the connectors hadn’t arrived in time to be assembled by machine, so I fitted them by hand in the lab. Pro tip: if you have to fit connectors by hand, take your time to ensure they are lined up correctly, and use lots of flux to help the solder flow into the joints. Sometimes people use very small soldering iron tips thinking it will help; in fact, one of the goals of soldering is to get heat into the joint, and if the tip is too small it will be difficult to heat the solder joint sufficiently to make a good connection.
Compute Module 4 IO Board
New features
Whilst it was easy to add some headline features like a second HDMI port, other useful features don’t grab as much attention. One example is that we have simplified the powering requirements. Previous Compute Modules required multiple PSUs to power a board, and the power-up sequence had to be exactly correct. Compute Module 4 simply requires a single +5V PSU.
In fact, the simplest possible base board for Compute Module 4 just requires a +5V supply and one of the connectors and nothing else. You would need a CM4 variant with eMMC and wireless connectivity; you can boot the module with the eMMC, wireless connectivity gives you networking, and Bluetooth connectivity gives you access to IO devices. If you do add extra IO devices the CM4 also can provide a +3.3V supply to power those devices, avoiding the need for an external power supply.
We have seen some customers experience issues with adding wireless interfaces to previous Compute Modules, so a really important requirement was to provide the option of wireless support. We wanted to be as flexible as possible, so we have added support for an external antenna. Because radio certification can be a very hard and expensive process, we have a pre-certified external antenna kit that can be supplied with Compute Module 4. This should greatly simplify product certification for end products, although engineering designers should check to make certain of meeting all local requirements.
Antenna Kit and Compute Module 4
PCIe
This is probably the most exciting new interface to come to Compute Module 4. On the existing Raspberry Pi 4, this interface is used internally to add the XHCI controller which provides the USB 3 ports. By providing the PCIe externally, we are giving end users the choice of how they would like to use this interface. Many applications don’t need USB 3 performance, so the end user can make use of it in other ways — for NVMe drives, to take one example.
Ethernet
In order to have wired Ethernet connectivity with previous Compute Modules, you needed to add an external USB-to-Ethernet interface. This adds complexity to the IO board, and one of the aims of the new Compute Module 4 is to make interfacing to it simple. With this in mind, we added a physical Ethernet interface to CM4, and we also took the opportunity to add support for IEEE1588 to this. As a result, adding Gigabit wired networking to CM4 requires only the addition of a magjack; no extra silicon is needed. Because this is a true Gigabit interface, it is also faster than the USB-to-Ethernet interfaces that previous Compute Modules use.
Open-sourcing the Compute Module 4 IO Board design files
Early on in the process, we decided that we were going to open-source the design files for the Compute Module 4 IO Board. We used our big expensive CAD system for Compute Module 4 itself, and while we could have decided to do the design for the IO Board in the big CAD system too and then port it across to KiCAD, it’s easy to introduce issues in the porting process.
So, instead, we used KiCAD for the IO Board from the start, and the design files that come out of KiCAD are the same ones that we use in manufacture. During development I had both CAD systems running at the same time on the computer.
Easier integration and enhanced possibilities
We have made some big changes to our new Compute Module 4 range, and these should make integration much simpler for our customers. Many interfaces now just need a connector and power, and the new form factor should enable people to design more compact and more powerful products. I look forward to seeing what our customers create over the next few years with Compute Module 4.
High-density connector on board underside
Get your Compute Module 4
The new Raspberry Pi Compute Module 4 is available from our network of Approved Resellers. Head over to the Compute Module 4 product page and select your preferred variant to find your nearest reseller.
Can’t find a reseller near you? No worries. Many of our Approved Resellers ship internationally, so try a few other locations.
It’s become a tradition that we follow each Raspberry Pi model with a system-on-module variant based on the same core silicon. Raspberry Pi 1 gave rise to the original Compute Module in 2014; Raspberry Pi 3 and 3+ were followed by Compute Module 3 and 3+ in 2017 and 2019 respectively. Only Raspberry Pi 2, our shortest-lived flagship product at just thirteen months, escaped the Compute Module treatment.
It’s been sixteen months since we unleashed Raspberry Pi 4 on the world, and today we’re announcing the launch of Compute Module 4, starting from $25.
Over half of the seven million Raspberry Pi units we sell each year go into industrial and commercial applications, from digital signage to thin clients to process automation. Many of these applications use the familiar single-board Raspberry Pi, but for users who want a more compact or custom form factor, or on-board eMMC storage, Compute Module products provide a simple way to move from a Raspberry Pi-based prototype to volume production.
A step change in performance
Built on the same 64-bit quad-core BCM2711 application processor as Raspberry Pi 4, our Compute Module 4 delivers a step change in performance over its predecessors: faster CPU cores, better multimedia, more interfacing capabilities, and, for the first time, a choice of RAM densities and a wireless connectivity option.
Raspberry Pi Compute Module 4
You can find detailed specs here, but let’s run through the highlights:
1.5GHz quad-core 64-bit ARM Cortex-A72 CPU
VideoCore VI graphics, supporting OpenGL ES 3.x
4Kp60 hardware decode of H.265 (HEVC) video
1080p60 hardware decode, and 1080p30 hardware encode of H.264 (AVC) video
Dual HDMI interfaces, at resolutions up to 4K
Single-lane PCI Express 2.0 interface
Dual MIPI DSI display, and dual MIPI CSI-2 camera interfaces
1GB, 2GB, 4GB or 8GB LPDDR4-3200 SDRAM
Optional 8GB, 16GB or 32GB eMMC Flash storage
Optional 2.4GHz and 5GHz IEEE 802.11b/g/n/ac wireless LAN and Bluetooth 5.0
Gigabit Ethernet PHY with IEEE 1588 support
28 GPIO pins, with up to 6 × UART, 6 × I2C and 5 × SPI
Compute Module 4 Lite, our variant without eMMC Flash memory
New, more compact form factor
Compute Module 4 introduces a brand new form factor, and a compatibility break with earlier Compute Modules. Where previous modules adopted the JEDEC DDR2 SODIMM mechanical standard, with I/O signals on an edge connector, we now bring I/O signals to two high-density perpendicular connectors (one for power and low-speed interfaces, and one for high-speed interfaces).
This significantly reduces the overall footprint of the module on its carrier board, letting you achieve smaller form factors for your products.
High-density connector on board underside
32 variants
With four RAM options, four Flash options, and optional wireless connectivity, we have a total of 32 variants, with prices ranging from $25 (for the 1GB RAM, Lite, no wireless variant) to $90 (for the 8GB RAM, 32GB Flash, wireless variant).
We’re very pleased that the four variants with 1GB RAM and no wireless keep the same price points ($25, $30, $35, and $40) as their Compute Module 3+ equivalents: once again, we’ve managed to pack a lot more performance into the platform without increasing the price.
To help you get started with Compute Module 4, we are also launching an updated IO Board. Like the IO boards for earlier Compute Module products, this breaks out all the interfaces from the Compute Module to standard connectors, providing a ready-made development platform and a starting point for your own designs.
Compute Module 4 IO Board
The IO board provides:
Two full-size HDMI ports
Gigabit Ethernet jack
Two USB 2.0 ports
MicroSD card socket (only for use with Lite, no-eMMC Compute Module 4 variants)
PCI Express Gen 2 x1 socket
HAT footprint with 40-pin GPIO connector and PoE header
12V input via barrel jack (supports up to 26V if PCIe unused)
Camera and display FPC connectors
Real-time clock with battery backup
CAD for the IO board is available in KiCad format. You may recall that a few years ago we made a donation to support improvements to KiCad’s differential pair routing and track length control features; now you can use this feature-rich, open-source PCB layout package to design your own Compute Module carrier board.
Compute Module 4 mounted on the IO Board
In addition to serving as a development platform and reference design, we expect the IO board to be a finished product in its own right: if you require a Raspberry Pi that supports a wider range of input voltages, has all its major connectors in a single plane, or allows you to attach your own PCI Express devices, then Compute Module 4 with the IO Board does what you need.
We’ve set the price of the bare IO board at just $35, so a complete package including a Compute Module starts from $60.
Compute Module 4 Antenna Kit
We expect that most users of wireless Compute Module variants will be happy with the on-board PCB antenna. However, in some circumstances – for example, where the product is in a metal case, or where it is not possible to provide the necessary ground plane cut-out under the module – an external antenna will be required. The Compute Module 4 Antenna Kit comprises a whip antenna, with a bulkhead screw fixture and U.FL connector to attach to the socket on the module.
Antenna Kit and Compute Module 4
When using ether the Antenna Kit or the on-board antenna, you can take advantage of our modular certification to reduce the conformance testing costs for your finished product. And remember, the Raspberry Pi Integrator Programme is there to help you get your Compute Module-based product to market.
Our most powerful Compute Module
This is our best Compute Module yet. It’s also our first product designed by Dominic Plunkett, who joined us almost exactly a year ago.
I sat down with Dominic last week to discuss Compute Module 4 in greater detail, and you can find the video of our conversation here. Dominic will also be sharing more technical detail in the blog tomorrow.
In the meantime, check out the Compute Module 4 page for the datasheet and other details, and start thinking about what you’ll build with Compute Module 4.
Reddit was alive with the sound of retro gaming this weekend.
First out to bat is this lovely minimalist, wall-mounted design built by u/sturnus-vulgaris, who states:
I had planned on making a bar top arcade, but after I built the control panel, I kind of liked the simplicity. I mounted a frame of standard 2×4s cut with a miter saw. Might trim out in black eventually (I have several panels I already purchased), but I do like the look of wood.
Next up, a build with Lego bricks, because who doesn’t love Lego bricks?
Just completed my mini arcade cabinet that consists of approximately 1,000 [Lego bricks], a Raspberry Pi, a SNES style controller, Amazon Basics computer speakers, and a 3.5″ HDMI display.
u/RealMagicman03 shared the build here, so be sure to give them an upvote and leave a comment if, like us, you love Raspberry Pi projects that involve Lego bricks.
And lastly, this wonderful use of the Raspberry Pi Compute Module 3+, proving yet again how versatile the form factor can be.
CM3+Lite cartridge for GPi case. I made this cartridge for fun at first, and it works as all I expected. Now I can play more games l like on this lovely portable stuff. And CM3+ is as powerful as RPi3B+, I really like it.
StereoPi allows users to attached two Camera Modules to their Raspberry Pi Compute Module — it’s a great tool for building stereoscopic cameras, 360º monitors, and virtual reality rigs.
My love for stereoscopic photography goes way back
My great-uncle Eric was a keen stereoscopic photographer and member of The Stereoscopic Society. Every memory I have of visiting him includes looking at his latest stereo creations through a pair of gorgeously antique-looking, wooden viewers. And I’ve since inherited the beautiful mahogany viewing cabinet that used to stand in his dining room.
It looks like this, but fancier
Stereoscopic photography has always fascinated me. Two images that seem identical suddenly become, as if by magic, a three-dimensional wonder. As a child, I couldn’t make sense of it. And even now, while I do understand how it actually works, it remains magical in my mind — like fairies at the bottom of the garden. Or magnets.
So it’s no wonder that I was instantly taken with StereoPi when I stumbled across its crowdfunding campaign on Twitter. Having wanted to make a Pi-based stereoscopic camera ever since I joined the organisation, but not knowing how best to go about it, I thought this new board seemed ideal for me.
The StereoPi board
Despite its name, StereoPi is more than just a stereoscopic camera board. How to attach two Camera Modules to a Raspberry Pi is a question people ask us frequently and for various projects, from home security systems to robots, cameras, and VR.
Slim and standard editions of the StereoPi
The board attaches to any version of the Raspberry Pi Compute Module, including the newly released CM3+, and you can use it in conjunction with Raspbian to control it via the Python module picamera.
StereoPi stereoscopic livestream over 4G. Project site: http://StereoPi.com
When it comes to what you can do with StereoPi, the possibilities are almost endless: mount two wide-angle lenses for 360º recording, build a VR rig to test out virtual reality games, or, as I plan to do, build a stereoscopic camera!
It’s on Crowd Supply now!
StereoPi is currently available to back on Crowd Supply, and purchase options start from $69. At 69% funded with 30 days still to go, we have faith that the StereoPi project will reach its goal and make its way into the world of impressive Raspberry Pi add-ons.
Today we bring you the latest iteration of the Raspberry Pi Compute Module series: Compute Module 3+ (CM3+). This newest version of our flexible board for industrial applications offers over ten times the ARM performance, twice the RAM capacity, and up to eight times the Flash capacity of the original Compute Module.
A long time ago…
On 7 April 2014 we launched the original Compute Module (CM1), with a Broadcom BCM2835 application processor, a single-core ARM11 at 700MHz, 512MB of RAM, and 4GB of eMMC Flash. Although it seems like yesterday, that was nearly half a decade ago! At that point I had no kids, looked significantly younger (probably because I had no kids), and had more hair (fortunately I’m still better off in that department than Eben). [This is fair – Ed.]
Just under three years later we launched Compute Module 3 (CM3) based on the quad-core BCM2837A1, and now, almost exactly two years on, we bring you the CM3+.
The Compute Module has evolved
While we’ve greatly improved the performance, RAM capacity, and Flash capacity of the Compute Module, some things remain the same: CM3+ is an evolution of CM3 and CM1, bringing new features while keeping the form factor, electrical compatibility, price point, and ease of use of the earlier products.
Our aim for the Compute Module was to deliver the core Raspberry Pi technology in a form factor that allowed others to incorporate it into their own products cheaply and easily. If someone wanted to create a Raspberry Pi-based product but found the Model A or B Raspberry Pi boards did not fit their needs, they could use a Compute Module, create a simple low-tech carrier PCB, and make their own thing.
It’s for enterprises of all sizes
We limit the price so that the “maker in a shed” is not disadvantaged when producing only a few hundred products relative to professionals with much larger production runs. The Compute Module takes care of the high-tech bits (fine-pitched BGAs, high-speed memory interfaces, and core power supply), allowing the designer to focus on the differentiating features they really care about. The eMMC Flash device on a Compute Module is more reliable and robust than normal SD cards, so it is more suited to industrial applications. The Compute Module also provides more interfaces than the regular Raspberry Pi, supporting two cameras and two displays, as well as extra GPIO.
CM3+ in CMIO board
CM1 and CM3 have proven very popular, with sales increasing steadily. We don’t generally get to see what the majority of our module customers are using them for, because they’re often companies that understandably want to keep the insides of their products secret, but one nice example application is Revolution Pi from Kunbus. Many NEC digital-signage displays incorporate a socket for CM3, and there are some excellent community efforts too, of which our current favourite is this nifty dual camera board. We’ve also seen enterprising companies start offering turnkey design services using the Compute Module, such as that offered by Kunst Engineering.
So what is Compute Module 3+?
CM3+ is derived from the CM3 board, but incorporates the improved thermal design and Broadcom BCM2837B0 application processor from Raspberry Pi 3B+. This means that, with the exception of a small increase in z-height, CM3+ is a drop-in replacement for CM3 from an electrical and form-factor perspective. Note that due to power-supply limitations the maximum processor speed remains at 1.2GHz, compared to 1.4GHz for Raspberry Pi 3B+.
One of the most frequent requests from users and customers is for Compute Module variants with more on-board Flash memory. CM1 and CM3 both came with 4GB of Flash, and although we are fans of the Henry Ford philosophy of customer choice (“you can have any colour, as long as it’s black”), it was obvious that there was a need for more official options.
With CM3+ we are making available three different eMMC Flash sizes, in addition to a Flash-less “Lite” variant, all at competitive prices:
As CM3+ is a new product, it will need a recent version of the Raspberry Pi firmware (and operating system such as Raspbian) to operate correctly.
Thermals
Due to the improved PCB thermal design and BCM2837B0 processor, the CM3+ has better thermal behaviour under load. It has more thermal mass and can draw heat away from the processor faster than CM3. This can translate into lower average temperatures and/or longer sustained operation under heavy load before the processor hits 80°C and begins to reduce its clock speed.
Note that CM3+ will still output the same amount of heat as CM3 for any given application, so performance (and particularly sustained performance) will depend heavily on the design of the carrier PCB and enclosure. As always, we recommend that product designers pay careful attention to thermal performance under expected use cases.
Having characterised the behaviour of the new product, we have broadened the rated ambient temperature range to -20°C to 70°C.
Development Kit
We are also releasing a refreshed Compute Module 3+ Development Kit today. This kit contains 1 x Lite and 1 x 32GB CM3+ module, a Compute Module IO board, camera and display adapters, jumper wires, and a programming cable.
CM3+ will be available until at least January 2026.
We are also moving the “legacy” CM1, CM3 and CM3 Lite products to “not recommended for new designs” status. They will continue to be available until at least January 2023 as previously stated, but we recommend customers use CM3+ for new designs, and where possible move existing designs to CM3+ for improved performance and longer availability.
Compute Module 3+ is, like Raspberry Pi 3B+, the last in a line of 40nm-based Raspberry Pi products. We feel that it’s a fitting end to the line, rolling in the best bits of Raspberry Pi 3B+ and providing users with more design flexibility in an all‑round better product. We hope you enjoy it.
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