Seeed Xiao M0
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The Seeed Xiao M0 features the same Cortex-M0 SAMD21 as the Arduino M0 but in a very compact form-factor.
The USB connector is a Type-C, which takes almost one third of the board. SeeedStudio has developed two expansions boards:
The board was sampled by Seeeduino. |
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Hardware
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The board has a DIP14 700 mil form-factor, plus castellated pins.
The board features 14 pins with all the standard ports, including two UART ports (one for USB, another on dedicated pins), I²C and SPI. The package includes three stickers with the functions of the pins, but the print is so small it is hard to read. Click to enlarge
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On the front side (left) close to the USB connector, a pad is labelled RESET. Four LEDs inform about power (green), UART (two blue for TX and RX), and finally a user's LED (orange), although in negative logic.
On the rear side (right), the Xiao board exposes pads for SWD clock and data signals, making debugging possible although requiring some soldering. Also are exposed pads for VIN and GND. |
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The second batch of the board exposes four pads for debugging: SWD clock and data signals, ground and reset.
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Software
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Seeed provides the adapted boards package for the Arduino IDE and a Wiki offers a very clear documentation. The board is also supported by embedXcode with external debugging.
One of the interesting part of the board is the multiple offer for uploading the firmware.
I had to try twice to upload successfully through Serial. UF2 is more stable, although the Seeeduino SAMD boards package does not include the required utilities. As last resort, the SWD option was very helpful in unbricking one of the boards and flashing the boot-loader again. |
Drag-and-drop the executable
onto the volume to flash the board |
Debugging
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The Seeed Xiao M0 exposes the SWD signals through SWCLK and SWDIO pads.
I connected the SWD signals SWCLK and SWDIO, power +5V and Ground, +3.3V VTref, serial RX and TX to my Segger J-Link Edu. The new Xiao Expansion Board exposes the SWD signals and makes debugging much easier. |
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I was able to debug with my J-Link Edu, with both the command-line J-Link utilities and the Ozone GUI from embedXcode.
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Conclusion
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At less than USD5, the Seeed Xiao M0 brings unrivalled value, with a compact form-factor with castellated connectors, powerful Cortex-M0, easy drag-and-drop for programming, and exposed SWD pads for debugging.
As a logical complement, I would love a Grove and SWD extension board featuring Grove connectors for I²C, UART and GPIO; two pogo pins for to connect to the SWD pads; and the standard 2x5 0.05" SWD fool-proof connector to use with the very affordable Segger J-Link Edu mini programmer-debugger. Even better, the Xiao can act as a $5 programmer-debugger against another Xiao! The USB-C cable is not included. Actually, it is almost as large and expensive as the board! |
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Pros
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Cons
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Wrap-Up
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