The previous post settled the gateway's Bluetooth chip: a Silicon Labs module runs the Mesh stack and takes commands from the host over UART. This post is about the other chip, the main processor that runs Linux and the gateway program.
There's far more choice here than for the Bluetooth chip. We looked at Rockchip's RK3506, RK3562 and RK3576, plus D-Robotics' RDK X5, which a partner company recommended. The conclusion wasn't to pick one chip but to offer three tiers by product positioning.
First, how much performance does a gateway really need?
Lay out the requirements and a lot of "high-end" turns out to be unnecessary:
| Requirement | What it takes |
|---|---|
| Gateway program | A single Rust program using a few dozen MB of RAM |
| Matter | Very little traffic; commissioning crypto is heavier but happens once |
| Network | Ethernet or Wi-Fi; 100 Mbps is plenty |
| Bluetooth module | One UART, with RTS/CTS hardware flow control (Silicon Labs BGAPI has no checksum) |
| System | Minimal Linux, read-only root filesystem, A/B partitions for OTA |
| Security | The Matter device certificate's private key needs protection, ideally with secure boot and OTP |
For a pure Bluetooth Mesh to Matter bridge, compute barely matters. What does matter: UART flow control, secure boot, SDK quality, long-term supply and price.
RK3506: the cheapest, enough for bridging
The RK3506 is a fairly new entry-level Rockchip chip:
- Three Cortex-A7 cores at 1.2 GHz, 32-bit, plus a Cortex-M0.
- DDR3L memory, typically 128 MB to 512 MB.
- 100 Mbps RMII Ethernet, no PCIe; Wi-Fi only over SDIO or USB.
- Flexible pin multiplexing with plenty of UARTs.
Core boards are cheap; Luckfox's Lyra modules with 512 MB RAM and 8 GB eMMC list at a little over 100 yuan (about US$15).
For a gateway it's enough: the program needs a few dozen MB, and three A7 cores handle Matter and Mesh translation easily. We confirmed the gateway program compiles for the RK3506's 32-bit ARM target (armv7-unknown-linux-musleabihf) without code changes.
Two caveats:
- Choose 512 MB. The 128 MB variants are too tight beyond a demo.
- Check secure boot, OTP and OP-TEE support first. The chip is new, documentation is thin, and this determines how the private key is protected for Matter certification.
The downsides are clear: 32-bit, little memory and no NPU leave almost no room for future features.
RK3562: some headroom, the mainstream choice
The RK3562 is our "standard" choice:
- Four Cortex-A53 cores at 2.0 GHz, 64-bit.
- LPDDR4, 1 to 4 GB.
- Gigabit Ethernet, PCIe, USB 3.0 and around ten UARTs.
- A 1 TOPS NPU.
MYIR, Forlinx, Industio and others sell core boards listed at roughly 150–300 yuan (US$20–40); development boards run 500–600 yuan.
The reason to choose it is headroom: 64-bit, gigabit Ethernet and 2 GB of RAM leave space for local automation, a web admin page or more protocols later. Rockchip's Linux SDK support is mature, and one Buildroot command produces a complete firmware image.
One lesson: buy the development board and the production core board from the same vendor. The BSP and device tree you develop against then match production, saving a porting round.
RK3576: only for a control panel with a screen
The RK3576 is a big step up: eight cores (4×A72 + 4×A53), a 6 TOPS NPU and much stronger display and video. Core boards start around 500 yuan (about US$70).
For a pure bridge it's clearly overkill. It suits a different product: a smart home control panel with a screen, such as a 7-inch wall display that shows device status and scenes while doubling as the gateway. The NPU would also help with local voice or AI features later.
RDK X5: workable, but not a good fit for a gateway
A partner company suggested D-Robotics' RDK X5. The specs are impressive:
- Eight Cortex-A55 cores at 1.5 GHz.
- A 10 TOPS BPU (D-Robotics' AI accelerator) and 4K video encoding and decoding.
- A module integrating RAM and eMMC, optionally with Wi-Fi 6 and Bluetooth 5.4.
- The 4 GB development board costs 549 yuan (about US$75).
Technically it runs a gateway fine: it's 64-bit ARM Linux, our program works as is, the needed interfaces are there, and there's a Buildroot SDK with a secure firmware option.
In a gateway, though, the issues pile up:
| Issue | Details |
|---|---|
| Wasted compute | The selling points are 10 TOPS and vision processing, which a gateway never uses |
| Cost | Module prices vary widely by channel and are clearly above the RK3562 overall |
| Ecosystem | A single vendor, with far fewer community resources and solution partners than Rockchip |
| System | The main image is Ubuntu desktop; production needs the Buildroot SDK, whose maturity needs checking |
| Maturity | The module documentation we found still said "product under development"; production status and supply need confirming |
| Duplicate Bluetooth | The Wi-Fi module also includes Bluetooth, but our Bluetooth is handled by a separate Mesh module, leaving an unused radio |
It's a great robotics and vision AI platform, just not the right base for a cost-sensitive gateway.
The four side by side
| RK3506 | RK3562 | RK3576 | RDK X5 | |
|---|---|---|---|---|
| CPU | 3×A7, 32-bit | 4×A53, 64-bit | 4×A72 + 4×A53 | 8×A55 |
| AI compute | None | 1 TOPS | 6 TOPS | 10 TOPS |
| Typical RAM | 128–512 MB | 1–4 GB | 4–8 GB | 2–8 GB |
| Ethernet | 100 Mbps | Gigabit | Gigabit | Gigabit |
| Listed core board price | ~US$15 | ~US$20–40 | From ~US$70 | Varies by channel |
| Ecosystem and SDK | New, thin docs | Mature | Mature | Single vendor |
| Best for | Bridging only, lowest cost | Bridging plus extras | Screen panel, AI | Robotics, vision AI |
Our choice: three tiers
| Version | Processor | Positioning |
|---|---|---|
| Budget | RK3506 | Bluetooth Mesh to Matter only, lowest cost |
| Standard | RK3562 | Headroom for local automation, web admin and more protocols |
| Premium | RK3576 | Control panel with a screen that doubles as the gateway |
All three share one software stack: Rockchip's SDK with Buildroot, with the gateway program built for different targets and identical Bluetooth modules and device firmware. That's the layered design from the first post at work: swap the processor and neither the Bluetooth nor the Matter layer changes.
For validation we start with an RK3562 development board, which has the most headroom and is easiest to debug. Once everything works, the same program moves to the RK3506 to bring costs down.
Questions to ask before ordering
Whichever chip you choose, ask the vendor these before buying boards:
- Can the UART run RTS/CTS hardware flow control, and are those pins broken out?
- How is the SDK delivered, does it include Buildroot, and which kernel version?
- What's the status and documentation for secure boot, OTP and OP-TEE?
- What's the production price and lead time for the core board, and is there an end-of-life plan?
- Which onboard Wi-Fi module is used, and is its driver already working?
Final thoughts
It's easy to let specs drive the choice of processor: cores, TOPS, RAM, always reaching for more. For a gateway, what decides success are the unglamorous details: UART flow control, secure boot, a usable SDK and long-term availability. Decide how far the product needs to go first, then decide how much performance to buy.
If you're choosing a processor for a smart home gateway, or customizing Buildroot with Rockchip's SDK, I'd be glad to talk: linktr.ee/weiyii
Cover image: Mbrickn, CC BY 4.0.
This article was prepared for DEV with AI assistance.
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