Xiao Expansion Board
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The Xiao Expansion Board is the perfect accessory for the Xiao board.
The board was designed in a very interesting way. Early July 2020, SeeedStudio asked the users to exchange ideas on the #Conceptual Design# Premier Expansion Board for Seeeduino XIAO - Grove XIAO thread. After various iterations on features and form factors, the board was available late November 2020. The board was sampled by SeeedStudio. |
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The SWD signals are rerouted from the Xiao board through pogo-pins to standard connectors.
They include SWDIO, SWCLK, RESET and GROUND. |
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The Xiao Expansion Board exposes the I²C bus and a Serial port, plus one analog input and one digital GPIO, with standard Grove connectors.
The board also features a battery-backed RTC (I²C), a micro SD-card slot (SPI), a battery circuit for charging, a buzzer and a 128x64 OLED screen (I²C). The battery-backed RTC is based on the NXP PCF8563 with a CR1220 coin-cell battery as back-up. Also included, a power management circuit with a switch and a connector for a LiPo battery. The 128x64 OLED screen is driven by the popular SSD1306 controller and is supported by the LCD_screen Library Suite. Although small, the screen is bright and crisp. |
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Pins map
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Debugging
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The board exposes the SWD signals SWDIO and SWCLK, plus Ground and 3.3V for VTref, and also TX and RX from Serial1. The Segger J-Link programmer-debugger supplies +5V to power the board.
Just connect the Segger J-Link programmer-debugger with female-female cables (except a female-male for +5V) and install the Segger J-Link software to start debugging. The Segger J-Link programmer-debugger reroutes the Serial port (here Serial1 on pins 6 and 7) to the USB. |
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When using the command-line J-Link utilities, the three terminal windows show, from left to right:
Click to enlarge
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The same configuration is here debugged with Ozone, a GUI debugger.
Ozone only needs the .elf fine to start debugging. The tests shown here were performed with embedXcode, embedded computing on Xcode. |
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Conclusion
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The unique combination of RTC, screen, micro SD-card slot, battery management and 4 Grove connectors makes the Xiao Expansion Board a perfect choice for data acquisition. The SAMD21 of the Xiao M0 offers plenty of memory and processing power.
The Xiao Expansion Board is priced at less than USD15 and, combined with the Xiao M0, totals less than USD20, a highly competitive price for a versatile solution. The only limitation is the absence of the standard 2x5 0.05" SWD fool-proof connector, which means it can't be used with the affordable Segger J-Link Edu mini programmer-debugger and requires a Segger J-Link Edu instead. The $5 programmer-debugger provides an elegant solution. Hint: it features a Xiao board! |
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Pros
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Cons
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Wrap-Up
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Posted: 12 Dec 2020
Edited: 18 Dec 2020
