Seeed Studio XIAO Plus, More Castellation IOs for SMD Soldering
The beloved Seeed Studio XIAO boards, with their surface-mount device (SMD) design and Castellated Mounting Holes, have become popular integrated system modules in countless creative designs, projects, and even commercial products. Their board-to-board soldering capability allows XIAO boards to be easily integrated into carrier boards, enabling faster assembly and scalable production.
Since launching our first XIAO SAMD21 (formerly Seeeduino XIAO) in 2019, we’ve received countless community requests for more than the standard 14 castellated mounting holes on two edges, as these weren’t sufficient for complex projects requiring additional IOs. Now, please meet Seeed Studio XIAO Plus – our response to this community feedback.
Inspired by the cool SMD pins design of the RICK TNY, Seeed Studio XIAO Plus represents a new iteration of our regular XIAO Boards, featuring redesigned 23 castellation pins (20 GPIOs, 3 power pins) and back solder points specifically for projects needing expanded IOs. We’re launching XIAO Plus versions for three models: XIAO ESP32S3 Plus, XIAO nRF52840 Plus, and XIAO nRF52840 Sense Plus, which are all available for instant order at our webstore and AliExpress Store.
Why only these three XIAOs?
While we’d love to upgrade all XIAO boards, the limited pins on some integrated chips (SAMD21, RP2040, RA4M1, ESP32-C3, and ESP32-C6) restrict the IO expansion. These three models were selected based on overwhelming user demand for additional castellated IOs. Moreover, the XIAO ESP32S3 Plus also doubles its Flash memory to 16MB, supporting more complex applications.
What's new with the back solder points?
Previously, XIAO boards lacked uniformity in their back-side solder points and layouts, hampering our ability to develop universal expansion boards. Our latest XIAO boards (RP2350, RA4M1, MG24 and MG24 Sense) share nearly identical back layouts. The XIAO Plus boards follow suit, with aligned battery and debugger pads.
This standardization means our upcoming expansion boards (such as the XIAO Clip Board) will work with all seven boards (3 XIAO Plus models, XIAO RP2350, RA4M1, and MG24/Sense). We’re actively working on compatibility solutions for other XIAO boards and will share updates once available.
Is XIAO Plus harder to solder?
The through-holes for 7-pin headers remain unchanged, but the castellated mounting holes are slightly smaller and closer together (13 on the left, 10 on the right). While this does make board-to-board soldering more challenging, our 11-person product team successfully tested it with early samples.
We’ll be honest – it requires more precision, but proper tools make a significant difference. Essential items include a brass sponge, water-soluble flux pen, tweezers, acid brush, and rubbing alcohol. For detailed guidance, check out SparkFun’s excellent tutorial on How to Solder: Castellated Mounting Holes.
Join Seeed Studio XIAO Adopter Program
Ready to showcase your soldering skills? Share your XIAO Plus project ideas in the comments! I’ll select three winners to receive their chosen XIAO Plus board (via coupon). Winners will be announced on January 10, 2025. Share now! To assist developers in adapting their projects to the XIAO Plus quickly, we’re adding all the XIAO Plus Boards to the Seeed Studio XIAO Adopter Program. If you’re an author or maintainer of a popular open-source project on GitHub, or an influencer on platforms like YouTube or Tiktok or Instagram, make sure your users can run your code on the XIAO Plus. Join to receive 2 free boards and technical support to make your code compatible with these exciting new boards.
Notes at the end.
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