Defining open hardware

Open-source hardware (or open hardware) refers to hardware that is developed in a manner similar to open-source software. There's a widely accepted definition of open-source hardware, but it is probably not as well known as its open-source-software counterpart. In addition, there is a popular certification program that hardware makers can use to indicate which of their devices meets that criteria. But there are some vendors that are showing more enthusiasm than others in participating in the process—or in producing open hardware at all.

The leading organization advocating for open-source hardware is the Open Source Hardware Association (OSHWA). Established in 2012, it provides a definition of open-source hardware based on the Open Source Definition maintained by the Open Source Initiative. The OSHWA definition's introduction describes its main principle as:

Open Source Hardware (OSHW) is a term for tangible artifacts — machines, devices, or other physical things — whose design has been released to the public in such a way that anyone can make, modify, distribute, and use those things.

This principle is then made explicit in 12 criteria that are not unlike the ten criteria of the Open Source Definition.

OSHWA recommends eight licenses for open-source hardware in its FAQ. These are divided into two categories: copyleft licenses, which require derivative works to be released under the same license, and permissive licenses, which allow for proprietary derivatives. Recommended copyleft licenses include the non-hardware-specific GPL and Creative Commons Attribution-ShareAlike (CC-BY-SA), as well as the hardware-specific CERN Open Hardware license and TAPR Open Hardware License. Recommended permissive licenses include the non-hardware-specific FreeBSD license, MIT license, and Creative Commons Attribution (CC-BY), as well as the hardware-specific Solderpad Hardware license.

It's important to note that, as with open-source software, licenses that prohibit commercial use are not compatible with the OSHW definition. Since the creation of hardware invariably involves money, it's difficult to make use of a hardware design without some form of commercial activity.

OSHWA also has a set of best practices for creators of open-source hardware projects. For example, these recommend sharing the "original source files that you would use to make modifications to the hardware's design". While the best practices encourage using FOSS software for designing the hardware, they acknowledge the reality of proprietary programs and file formats in this domain and allow their use.

If we limit ourselves to printed-circuit boards (PCBs) such as microcontroller boards and single-board computers, then what needs to be shared includes mechanical drawings, electronic schematics, a bill of materials, and the design of the printed-circuit-board layout. If any of these components is lacking, the hardware can't be recreated.

One prominent example of hardware with limited information is the Raspberry Pi single-board computer. While some electronic schematics are published, they primarily show the pinouts of the connectors. These reduced schematics are useful for users or those who want to design add-on boards, but not for those who want to make their own version of a Raspberry Pi. According to the license information, the schematics are using the Attribution-NoDerivatives 4.0 International (CC BY-ND) license, which is not an open-source hardware license because it does not allow derivative works.

Self-certification program

In 2016, OSHWA set up a certification program, which relies on creators to voluntarily self-certify their projects. Doing so allows them to use a logo indicating their compliance with the OSHW definition.

OSHWA has the authority to revoke a certification, as it has done on a few occasions. The first time was in 2018 for the Motedis XYZ 3D printer because the project's documentation link was no longer working. After OSHWA was unable to obtain a copy of the documentation from the contact person in the certification application, the organization revoked the certification. This also happened for the Atmel SAM D10C Breakout Board by San Antonio Technologies for the same reason.

In 2022, OSHWA started publishing documentation for decertified hardware. This was possible because OSHWA had been archiving documentation as part of the certification process for a few years. In cases where the documentation is no longer available on the manufacturer's web site, OSHWA now publishes the documentation as part of the decertification process.

Earlier this year, OSHWA revoked the certification of the SparkFun DataLogger IoT – 9DoF. This was done at the request of SparkFun "due to accidental filing". While the hardware for the project was open-source, the firmware was not. This came as a surprise to users, because SparkFun is considered a big proponent of open hardware. SparkFun CTO Kirk Benell explained in a GitHub issue: "The OSHWA logo/cert was a mistake made by our system when we build [sic] the board -- everything ran on automatic and it wasn't checked before the release".

The list of certified open-source hardware projects on OSHWA's web site includes over 2,500 projects. These encompass a wide range of devices, including Arduino boards, add-on boards for Arduino and Raspberry Pi, drone flight controllers, 3D printers, smart speakers like the Mycroft Mark 1, and even electric vehicle charging stations. Adafruit, with almost 700 certified products, and SparkFun, with almost 600, have a significant presence on the list. Many of these certifications are for Arduino-compatible boards. Olimex, a smaller player, has 68 certified products, including ESP32 boards and its OLinuXino line of single-board computers running mainline Linux.

Each product page on the certification web site provides a direct link to the product's documentation. However, the hardware and software files are not directly accessible. To find the hardware schematics, you need to visit the referenced project web site and search for the appropriate files on that page. For example, for Adafruit products the hardware schematics are linked under the Technical Details header, while for SparkFun products the Documents tab shows them. Olimex shows a link to the hardware schematics under the Hardware heading.

In its blog article about the first decertification, OSHWA explained that it is trying to reduce duplication of effort, which is why it doesn't just serve the hardware's documentation on its own web site:

Developing and maintaining a feature-complete documentation hosting solution is beyond OSHWA’s core competency. Many good solutions for developing and maintaining software and documentation already exist online. Requiring certifiers to update and maintain yet another repository of documentation in order to certify was determined to be unnecessarily burdensome.

Other places to find open hardware

There are various other places where you can find open hardware that isn't necessarily following the OSHWA certification program. For example, OpenHardware.io contains more than 500 projects. For each project, a page shows the license, photos, a description, a bill of materials to order the parts, the source code for the associated software, and all the necessary design files for the hardware. The web site hosts sensor boards, relays, LED controllers, remote controls, Arduino and Raspberry Pi add-on boards, adapters and more. A lot of projects are still indicated as a "work in progress", though.

Kitspace hosts a smaller selection of interesting electronic designs. Notable offerings include a tiny Arm microcontroller board that fits into a USB port and barely protrudes, a tiny Arduino-compatible board, a WiFi air-pollution sensor board, and boards for the ESP8266 and ESP32 microcontrollers. The web site is sponsored by some PCB manufacturers, which results in direct links to these manufacturers from the product page to order the PCB.

Open hardware doesn't have to be about electronics, though. Thingiverse, a well-known web site in the world of 3D printing, provides a diverse range of open designs for 3D objects. Anyone can produce these objects with their own 3D printer using the shared STL files. Thingiverse offers a lot of tools and ornaments, as well as designs for enclosures for various microcontroller boards or SBCs.

Arduino and OSHWA

One of the most well-known open-hardware projects is Arduino, which offers microcontroller boards with an accompanying open-source development environment. The electronic schematics and design files of its boards are available under the CC-BY-SA license. This allows anyone to recreate these Arduino boards, although without using the trademarked Arduino name.

What is somewhat strange, though, for such a notable company in the open-hardware ecosystem, is that OSHWA's list of certified open-source hardware doesn't contain any official Arduino boards. Those boards seem to tick all of the boxes of the OSHW definition, but Arduino has chosen not to certify its products. That's even more surprising if you know that the list of endorsements of the OSHW definition includes Arduino founders Massimo Banzi, David Cuartielles, David Mellis, and Tom Igoe. They even helped create the definition. But when Adafruit recently asked Arduino if they would consider certifying any of its boards, the company declined.

Still, aside from a few mistakes with missing design files and licenses, Arduino has been releasing all of its boards as open hardware. This changed with the introduction of the Arduino Pro hardware, as Adafruit pointed out in a 2021 blog post. The product page of the Portenta H7 board only lists schematics and a data sheet, omitting the design files necessary for manufacturing the board. For a long time, Arduino's introduction page claimed: "All Arduino boards are completely open-source, empowering users to build them independently and eventually adapt them to their particular needs."

When Adafruit asked about this discrepancy, Arduino's Alessandro Ranellucci replied that, for the Arduino Pro line, the company wanted to "prevent counterfeiters from blindly downloading a file and manufacturing it without any R&D effort or contribution to the community". As a result, the company decided to publish the schematics without the design files necessary for manufacturing the board. The original statement on the introduction page has since been removed, and the page now says: "The plans of the Arduino boards are published under a Creative Commons license, so experienced circuit designers can make their own version of the module, extending it and improving it."

For now, Arduino seems to uphold its promise to keep its "products for makers" as open-source hardware (although not OSHWA-certified), but does not do the same for its Pro line; boards such as the Portenta C33 and the Portenta X8 have been released without design files. It's a bit concerning, though, that the newest non-Pro boards (like the Arduino Nano ESP32 and the Arduino UNO R4 WiFi) don't even mention "open" on their product pages or in their documentation. It's unfortunate that a big player like Arduino isn't taking a clearer position on open hardware.

As the OSHWA list of certified projects, along with other directories such as OpenHardware.io, Kitspace, and Thingiverse, show, there is already a lot of open hardware. We can hope that Arduino changes heart and renews its commitment to keep its products for makers open, whether OSHWA-certified or not. Arduino plays a significant role in this space, not only with its hardware, but also with its software ecosystem. Fortunately, companies such as Adafruit, SparkFun, and Olimex make a big effort to certify their hardware. So, those who wish to build upon OSHWA-certified hardware have a lot of alternatives to Arduino boards to choose from.