HAT and HAT+
A HAT follows the mechanical outline and 40-pin header for Raspberry Pi. An ID EEPROM lets the system load the matching device-tree overlay. This form fits when the product should sit on a Raspberry Pi and stay mechanically predictable.
Electronics and embedded Linux
HAT, shield, and carrier development for Raspberry Pi
Product-specific boards for use with Raspberry Pi single-board computers and Compute Modules. Schematic, PCB, ID EEPROM, device tree, and bring-up – and the software around the board when the board is only one part of the device.
Three board types, one development path
HAT, shield, and carrier answer different mechanical questions. Electrically the job is the same: a board that fits the product and boots cleanly.
Shield
Shield is the older, looser name for a stackable add-on. We use it when the HAT outline, height, or connector placement does not fit the device – a taller stack, a custom connector leaving the header, or a board that has to clear existing mechanics.
Carrier
A carrier is the baseboard a Compute Module plugs into. It provides power, storage, Ethernet, USB, display or camera links, and the I/O the product needs. ATHENA’s control electronics are built this way: a Compute Module for Raspberry Pi plus a realtime co-MCU, integrated into the machine.
What belongs in a board you can build
- Schematic and PCB layout, including the 40-pin or module connector
- Power architecture, protection, and connector choice
- ID EEPROM and device-tree overlay for HATs
- Co-MCU and firmware when realtime I/O does not belong on Linux
- Linux image, boot, and interface bring-up
- Mechanical fit: outline, standoffs, enclosure
- Prototype and manufacturing data for the next revision
Typical starting points
The prototype still lives on a generic HAT
Jumpers or a catalogue board were enough to prove the idea. The product still needs its own I/O, a defined power tree, or a form that can be manufactured.
The Compute Module is chosen, the carrier is not
Interfaces and the enclosure are sketched. The baseboard that brings the module into the device has not been designed.
An existing board is not ready for production
It boots unreliably, or power, EMI, or the overlay are not yet solid enough to manufacture.
The board has to meet the rest of the system
Mechanics, a local UI, or a backend are part of the product. A bench test on its own does not describe it.
Reference
A Compute Module inside the product
On ATHENA, Layershift delivers the control electronics around a Compute Module for Raspberry Pi and a realtime co-MCU – including firmware, system integration, and the update path. The product belongs to Concepts 3D. The reference shows how a carrier lands in a connected device.
Common questions
Do you design HATs for Raspberry Pi?
Yes, when the HAT or HAT+ outline is the right form – including the mechanical grid, 40-pin header, and ID EEPROM. We also design boards that deliberately leave that outline. These are Layershift designs for use with Raspberry Pi, not products of Raspberry Pi Ltd.
What is the difference between a HAT, a shield, and a carrier?
A HAT is the specified add-on for the 40-pin header. A shield is a stackable expansion used when that specification does not fit mechanically. A carrier is the baseboard for a Compute Module and replaces the Raspberry Pi single-board computer inside the device.
Can you take over an existing prototype board?
Yes. Existing schematics, layouts, and images can be reviewed, stabilized, and continued – with a clear read on what is still open.
Do you deliver only the PCB?
The board can be the whole engagement. It can equally be the electronics part of a development that includes firmware, a Linux image, and the link to mechanics or cloud.
Which modules does this cover?
Current Raspberry Pi boards with a 40-pin header, and Compute Modules. The generation is chosen for the product, not from a fixed catalogue list.
Describe the board that is missing
The module, whatever already exists, and what the board has to do in the device are enough for an initial assessment.
Layershift is not affiliated with, endorsed by, or sponsored by Raspberry Pi Ltd. Raspberry Pi is a trademark of Raspberry Pi Ltd.