This article summarises the differences between Caravel, Caravan, OpenFrame and Caravel Mini to help you do an informed decision on which one to use
Caravel, Caravan, OpenFrame and Caravel Mini are all platforms provided by Efables, they serve as a template for designers to integrate their own projects into a pre-defined chip infrastructure, making it easier to get their designs fabricated through Efabless' shuttle service.
Standard SoC Template - Caravel
Caravel is the most prominent and widely used chip template from Efabless, supporting analog, digital, and mixed-signal designs. It is highly recommended for all users due to its ease of use. Caravel features a RISC-V processor and includes additional functionalities such as UART, SPI, and SRAM.
Bare Pad Prototyping (non-production) - Caravan
Caravan shares the same peripherals as Caravel, with the addition of 11 high-speed bare pads. This template supports analog and mixed-signal designs and is suggested for prototyping by experienced users. The inclusion of bare pads without ESD protection necessitates careful design to avoid potential issues. It is also recommended for lab use, with ESD protection to avoid potential risks.
Advanced Directly Configured IO - OpenFrame
OpenFrame is tailored for experienced users, offering only Caravel's padframe without any peripherals. This template is highly flexible, providing access to more I/Os and a larger area. However, users will not have access to the RISC-V processor or the additional peripherals found in Caravel. Additionally, the GPIOs in OpenFrame are more challenging to configure and require an experienced user to set them up correctly.
Small Design Prototyping - Caravel Mini
Caravel Mini is an ideal platform for prototyping small designs that don't need the full user_project_wrapper, making it a cost-effective choice with substantial benefits. This template allows you to share your work with others while keeping your project private if desired. The parts will arrive preconfigured to ensure that only your design is accessible, with no access to other projects on the same chip.
Template Summary
| Template |
Caravel
|
Caravan
|
OpenFrame
|
Caravel Mini
Small Design Prototyping Template |
| Price | $9,7500 | $9,7500 | $9,7500 | $3,500 |
| GPIOs | 38 Programmable | 27 programmable, 11 bare pads (no ESD) | 44 configurable | 36 Programmable |
| Processor | RISC-V SoC | RISC-V SoC | None | RISC-V SoC |
| User Area | ~10 mm² | ~10 mm² | ~15 mm² | ~2 mm² |
| Usage | Production & Prototyping | Prototyping | Production & Prototyping | Prototyping |
| Design Support | Digital, analog, or mixed-signal designs | Analog prototyping | Digital, analog, or mixed-signal designs | Digital designs |
| PCB | 1 Eval Board & 10 Daughter cards | 1 Eval Board & 10 Daughter cards | 1 Eval Board & 10 Daughter cards | 1 Eval Board & 2 Daughter cards |
Which Template Should I Use?
If you're a beginner, we strongly recommend using Caravel. Caravel is the most widely used and taped-out chip from Efabless, offering most of the interfaces beginners need and making it easy to integrate your design. Caravel is also suitable for many intermediate and advanced users, especially if low power or high-frequency designs are not a priority.
For advanced users prototyping an analog design that requires high-frequency bare pads, Caravan is a good option. However, due to the lack of ESD protection, we advise testing it in a lab environment with ESD protection.
For advanced users looking to create a custom SoC with a larger user area and more IOs, OpenFrame is a good option. However, unlike Caravel, OpenFrame requires special IO configuration that is not provided by default.
If you're a beginner with a cool idea for a small design, Caravel Mini is the perfect choice. It's cost-effective and packed with features that beginners will find useful. Additionally, your design will remain private, allowing you to take it to the next level and prepare it for production if desired.
References
Caravel/Caravan/OpenFrame Github repo
OpenFrame Blog
Caravel user project Github repo
Caravan user project Github repo
OpenFrame user project Github repo
Caravel Mini Github Repo
Caravel Mini user project Github Repo
Caravel Mini Blog