#Conceptual Design# Premier Expansion Board for SeeeduinoXIAO - Grove XIAO Plus - waiting for inputs

Here is Grove XIAO Plus - A conceptual design for the Premier Expansion Board for SeeeduinoXIAO. How do you think about it? Which one do you like most?

More specifically questions you may help:

  • Do you think this premier expansion board fits your demands?
  • Which function do you like most?
  • Is there anything you want to add or remove?
  • What would you like to do with Seeeduino XIAO?
  • Which function do you think you would use frequently and would like to have an expansion board for it?
  • Do you want a board with more functions with a bigger size, or a tiny board with specific function you need?
  • Is the appearance and layout design matters for you?
  • What color do you like?

Your opinion will be very valuable for us since we are always aiming at making products that better fit your requirements.

Welcomed to add any inputs to help us make the product better.


That’s great news!

I would go for designs A, C and E, with the following comments.

Design A

  • Doesn’t the SAMD21 MCU already include an RTC? So we could get rid of the additional RTC IC.
  • Red as colour is fine.
  • The two Grove connectors below the screen may hide it.
  • The real estate saved by removing the RTC IC and the two Grove connectors below the screen may be used to
    • either reduced the size of the board,
    • or add climate sensors (e.g. BME280 or BME680) and IMU (e.g. BNO055).

Design C

  • I like the balance of number of Grove connectors and constrained size.
  • Isn’t there room enough to add an external SPI Flash for Python?

Design E

  • I like the compact size.
  • What is the orange element below the SWD connector?

Other questions

  • The boards show 4 POGO pins: are they compatible with the first release of Xiao boards (left)?

All my 4 Xiao boards are from the first release.

  • If the 4 pads are required (right), how to change the first generation board for the second?

  • Have you considered a Premier Expansion Board with an Adafruit Feather form-factor?

  • Is there an ETA for the board?

Thanks for you in-time and informative answer. Just quickly answer some of your questions first:

  1. On-board SPI Flash is being considered for each design.
  2. The orange element below the SWD connector is designed as ICSP connectors, but now it is considered not necessary.
  3. The first release of Xiao has two pins for SWD so yes you could use SWD. But you could not use the quick reset key on-board since no RESET pin led out.
  4. Adafruit Feather form-factor has been considered and I’ve made some design like this:
    But as you could see the space is too limited to add more components and I am not sure the advantage of making in this form-factor so I didn’t use this.
  5. Thank you for pointing out that RTC IC is already in XIAO, adding a battery for RTC will be enough.
  6. So far I could not give a confirmed date for ETA for the board, normally we would prefer to spend more time on the product definition to make the product better fit users’ demands. Will let you know as soon as possible.

If you don’t mind, I would like to know more about:

  • What you normally use Seeeduino to do?
  • How frequently will you use the debug function, and for what particular purpose if any?
  • Is RTC function important for you?
  • What do you think would be the advantage to design in Feather form-factor?
  • Why would you like to have climate sensors onboard?

Thank you for your valuable input. It really helps! Will be glad to hear anything else you would like to share with us.

I’m using Seeeduino Xiao for fast prototyping. The powerful MCU and compact form-factor make it ideal to be embedded directly into the finalised product.

Design E meets this use case.

Powerful MCUs make large projects possible, hence the need for debugging. I use debugging to identify and fix bugs, and also to improve speed in critical functions.

I really like the Segger Edu mini and Ozone GUI debugger tools, managed from Xcode using the embedXcode plug-in. Please refer to my review of the Seeduino Xiao board and the connection currently required before the Premier Expansion Board.

RTC is interesting for low-power operations. The core MCU is in deep sleep and the RTC wakes it up to perform tasks.

The Feather form-factor is an emerging and popular format, with a rich set of FeatherWings, or shields in Adafruit parlance.

Boards with a rich set of sensors is a growing category. See for example Adafruit Clue, Arduino Nano 33 BLE Sense, BBC micro:bit, Microsoft Azure IoT DevKit to name a few.

Design A could fit into this category.

If you need a beta-tester, feel free to contact me!

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That‘s so informative and useful! We will take all your opinion into consideration and accelerate the product development process.

Thank you for your kind offer, and we will be glad to contact you when a beta-tester is needed. You are such a warmhearted participant in our product design process, and we are also looking for rangers, if you are interested, detailed could be found in:

Thanks again for the valuable inputs~

@ming.wen You’re welcome! I applied to the Seed Rangers Program and completed the form.

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I have revised the design based on users’ opinions collected. Octagon and Credit Card version have been added. May have a look and choose your preferred one. Also welcome to share your thoughts on further design.

I am not a big fan of the hexagonal board I, as its shape makes it difficult to use in a standard context.

One of the unique feature of the Xiao is its compactness. So I would prefer III over II. Now, the micro-SD card slot and the battery cell holder could be easily added on the rear side of the board.

On the III proposal, are the Grove connectors vertical or horizontal?

All those new options do not discard the minimalistic initial E option.

The only reason I am hesitate with E version is the lack of Grove interface and GPIOs ledout, which we deem important more application possibilities and debug scenario. And this is the most important reason that I consider a hexagonal shape, since it has enough side boundary to accommodate those connectors need to be put toward outsides. Compare to a 6565mm square, do you think a 6565mm hexagonal would be also fine to assembly?
Put the micro-SD card slot and the battery cell holder on the backside will definitely save a lot of space, but would also cause difficulty in using and assembling the board to a flat surface. What do you think?

I might have misunderstood model E. For me, it shows 3 Grove connectors.

Back to my initial post, I see two use cases.

1. Development expansion board

The aim is to facilitate development with the SWD plug for debugging, all pins exposed and 3 or 4 Grove connectors for external devices.

2. Expansion board

The goal is to provide a set of must-have peripherals like extra Flash, microSD-card slot, battery for RTC, screen, battery manager, RGB LED, all pins exposed and obviously plenty of Grove connectors.

This second use case could be expanded with a set of climate sensors (temperature, humidity, pressure, air quality, light, UV, sound, …) through one single I²C bus.

  • To answer your question,

I would prefer a square board rather than an hexagonal one. Another criteria is the final price, which needs to be consistent with the affordable Xiao.

“Are the Grove connectors vertical or horizontal?”
For easy plug for testing and debugging scenario, Grove connectors are all vertical. And horizontal connectors will take more space also. So which one you prefer?

For the III project, I would prefer horizontal Grove connectors to ensure a good reading of the screen.

I see. Thanks for bringing out this important issue.
I have made a test just now. While connecting the cables to the vertical Grove interface on both side of the screen, the screen will be also read without sight block. For not making the board any bigger, it seems to have the vertical Grove would be a better choice.

I like the idea of expansion boards but I don’t think I would go too big. For me the reason I picked the Xiao was because it was super small. I would probably pick another board if I was doing a more complex project. In addition, the small amount of flash memory on the Xiao makes it really hard to do complicated projects as you quickly run out of memory for library files (in my project I could only just get the HID library on it - didn’t even have room for the neopixel library).

I would take a look at all the connectors you’ve added and then see if you can actually have room to include all of the libraries on the Xiao. If not, thats probably a good sign that you need to reduce the amount of functionality it has.

PS… if you released a Xiao+ with more memory it would be my go to dev board for SO MANY of my projects that I currently use adafruit products for.

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Thank you for detailed input.
Yes, the memory issue has been seriously considered in the design. You could see in the first picture there is an on-board SPI-FLASH. And there is a TF card holder as well, enables to add extend tf card for more memory.
Actually, even on the latest released basic expansion board for Seeeduino XIAO, there is a bonding pad reserved for extend SPI-FLASH. May have a look at:

May I ask how big will be your prefered memory space for an onboard SPI-FLASH?
Welcome to share more thought on this.
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@reivilo @hellweaver666 @salman
Hi everybody, thanks for the detailed inputs. Just want to update the new version design of Premier Shield for Seeeduino XIAO as below:

And we have made some special designs for the silk print. Please let us know how would you like them.

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If I’m honest, I don’t really like the special designs. I would be perfectly content with black.

I wanted to check, the i2c port, is that compatible with the Adafruit Stemma/Sparkfun qwiic standard for i2c boards? Would I be able to put circuitpython code on the SD card? RESET BUTTON! YESS!

Happy to test one if you want to send it to me :wink:

Hi, Hellweaver. Thank you for your quick reply. What a pity you don’t like the colorful design.

For your question, as long as the signal pin sequence is the same, IIC port on the board will be compatible with the Adafruit Stemma/Sparkfun qwiic module. However, even you could plug it in Grove interface, these two interfaces are not the exactly the same on their shape, we do not recommend to do so for avoiding unexpectable damage of the connector.

P.S.: Grove - Qwiic Hub could allow you to either use Qwiic/STEMMA QT modules on Grove controller or use Grove modules on Qwiic/STEMMA QT controller. Please refer to:

The card slot is designed for expanding memory, so yes you could put circuit python code on it as well as other libraries you need, which makes more possibilities for Seeeduino XIAO.

We currently released a Seeed Ranger Program. Seeed Ranger could apply for free Seeed Products for project use from time to time. Should you be interested in this program, please visit:

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I am not a big fan of the special designs. It may appeal for a limited batch, but since the expansion board is touted as “premier” or “professional”, black is better.

I have mixed feelings about the new design. It tries to merge the two scenarios I’ve mentioned earlier, a Development expansion board and an Expansion board.

1. Development expansion board

I strongly recommend using a SWD connector instead of the 0.1" pins of the last iteration. The SWD connector is fool-proof and standard debuggers like the Segger Edu mini comes with the right cable to plug and play.

I would prefer design E or C.

2. Expansion board

As an expansion board, the last iteration lacks a second I²C Grove connector. As I²C is very popular for connecting Grove sensors and devices, I would expect a second I²C connector. I would prefer design A or design II or III.

Other comments

  • Doesn’t the SAMD21 MCU already include an RTC? So we could get rid of the additional RTC IC.
  • I would prefer a battery holder to another connector for the RTC battery (as in design A).
  • Do all designs include an SPI Flash memory, required for Python?


  • I am not sure about the screen. So I would go for design III with a screen or design C without. Both bring a large number of Grove connectors within a constrained size, and could answer the two scenarios I’ve exposed earlier.

Seeed Ranger Program

I’ve applied to the Seeed Ranger Program and I’m awaiting the answer.

Choosing the hardware wasn’t easy as I’ve already ordered most of it, including boards and peripherals.

I like the classical type, but if I hada to make a choice, I’d choose either the “chocolate” or the lower right pink version. I love the OLED display, my Xiao for Grove doesn’t have it!

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