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Seeed Xiao SAMD21 Plus - 27 GPIO/Li-ion charging - Arduino/CircuitPython - Seeedstudio 100031394
XIAO SAMD21 with 27 digital pins, a battery charger and Reset and Boot buttons: a 21 x 17.8 mm board for Arduino and CircuitPython.
- 16 additional SMD pads on the bottom of the board
- 11 analog inputs and a DAC output
- Programmable WS2812 RGB LED
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SAMD21 with buttons, an RGB LED and a battery charger
Seeed Studio XIAO SAMD21 Plus is a board with an ATSAMD21G18A microcontroller that offers 27 digital pins, 11 analog inputs and a Li-ion charger in just 21 x 17.8 mm. The Cortex-M0+ core runs at 48 MHz and has a native USB interface, so the board can work as a keyboard, a macropad, meaning a small keyboard with shortcut buttons, or a MIDI controller connected to a computer.
The board has Reset and Boot buttons and a programmable WS2812 RGB LED. You get 32 KB SRAM, 256 KB flash and one DAC output, meaning a digital-to-analog converter that produces a voltage from 0 to 3.3 V. You can program the board in Arduino, PlatformIO, MicroPython, CircuitPython or Zephyr.
Seeed Studio XIAO SAMD21 Plus - top view
27 GPIO
digital pins (standard XIAO SAMD21: 11)
11 ADC + 1 DAC
analog inputs and one analog output
about 200 mA
Li-ion battery charging current via USB Type-C
Reset and Boot
two buttons instead of pads to short
Seeed Studio XIAO SAMD21 Plus - bottom view with solder pads
What the Plus version adds
The front of the board is the same 14-pin XIAO layout that works with add-on boards such as the XIAO Expansion Board, the Grove Shield for XIAO and the 1.28" round touch display for XIAO. On the bottom, the Plus version has 16 additional SMD pads with 1.27 mm pitch, meaning solder pads for soldering the board directly onto your own PCB.
The new pads provide a second I2C bus and an I2S interface, meaning a digital audio link for microphones and amplifiers. You connect a 3.7 V Li-ion battery to the BAT pads, the power management chip charges it, and you can read its voltage in your program. On the standard XIAO SAMD21, the power pads on the bottom are not suitable for connecting a Li-ion battery, because the board has no charging circuit.
Botland is an official distributor of electronics and robotics solutions from Seeedstudio. Hundreds of ready to use devices, components and modules are available from stock or to order. Our team guarantees that all Seeedstudio products presented here are original.
Is it the right choice for you?
A good choice if:
- you are building a USB device, such as a macropad, a keyboard or a MIDI controller
- you need many analog inputs and a DAC output in a small module
- you want to power your project from a Li-ion battery without a separate charger
Consider another option if:
- 11 pins and USB power are enough for you: choose the standard XIAO SAMD21
- you need more RAM and two cores: see the XIAO RP2040 Plus
XIAO SAMD21 Plus vs. standard XIAO SAMD21
| XIAO SAMD21 Plus | XIAO SAMD21 | |
|---|---|---|
| GPIO pins | 27 | 11 |
| Interfaces | 2 x I2C, UART, SPI, I2S | I2C, UART, SPI |
| Additional 1.27 mm SMD pads on the bottom | 16 | none |
| Li-ion battery charging | yes, about 200 mA | no |
| Buttons and LEDs | Reset and Boot buttons, WS2812 RGB LED | RST pads to short, L LED |
| See | this page | XIAO SAMD21 |
Fun fact
The XIAO family started with this board
The XIAO SAMD21, previously called Seeeduino XIAO, was the first thumb-sized board in the XIAO family. In the first version you reset the board by shorting two RST pads with tweezers, while the Plus version has separate Reset and Boot buttons.
Source: Seeed Studio Wiki: XIAO SAMD21
Frequently asked questions
How do I enter bootloader mode?
Connect the board to your computer and quickly press the Reset button twice. The board enters bootloader mode and waits for a new program.
Which board should I select in the Arduino IDE to upload code?
After installing the Seeed SAMD board package, select the XIAO M0 Plus board. The RGB LED is connected to pin PA27, and you switch on its power with pin D11.
How do I read the battery voltage?
Enable pin PB2 (VBAT_EN), read analog input PB3 (AIN11_VBAT) and multiply the result by 2. The battery is charged with a current of about 200 mA.
Package contents
- 1 x Seeed Studio XIAO SAMD21 Plus board
- 2 x 7-pin gold pin headers
The gold pin headers are not soldered.
Technical specifications
| Parameter | Value |
|---|---|
| Microcontroller | Microchip ATSAMD21G18A, Arm Cortex-M0+ up to 48 MHz, native USB |
| Memory | 32 KB SRAM, 256 KB flash |
| Wireless connectivity | none |
| Pins | 30 GPIO: 14-pin XIAO layout and 16 additional SMD pads; 27 digital pins |
| Analog inputs | 11 |
| DAC output | 1 |
| Interfaces | 2 x I2C, UART, SPI, I2S, SWD pads |
| On the board | WS2812 RGB LED, charging LED, Reset and Boot buttons |
| Battery management | SGM40567 Li-ion charger (about 200 mA), BAT-3V3 protection, battery voltage measurement |
| Power supply | USB Type-C 5 V; Li-ion battery 3.7 V via BAT pads |
| Software | Arduino, PlatformIO, MicroPython, CircuitPython, TinyGo, Zephyr |
| Operating temperature | -40 °C to 85 °C |
| Dimensions | 21 x 17.8 x 5 mm |
| Manufacturer code | 100031394 |
| Manufacturer | Seeed Studio |
Useful links
| Name | Value |
|---|---|
| UC - Microcontroller | ATSAMD21G18 |
| UC - Core | ARM Cortex-M0+ |
| UC - Flash | 256 kB |
| UC - RAM | 32 kB |
| UC - core | 1. Single Core |
| UC - Digital pins | 27 |
| UC - analog in | 11 |
| UC - freq | 48 MHz |
| UC - A/C | 12-bit |
| UC - USB | USB C |
| UC - I2C | yes |
| UC - UART | yes |
| UC - Connector | USB typ C |
| UC - SPI interface | yes |
| Width | 4.5 cm |
| Height | 2.5 cm |
| Depth | 2.5 cm |
| Weight | 0.01 kg |
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30 days to return, without giving a reason
If the product does not meet your expectations, you have 30 days from receiving the parcel to withdraw from the contract. The product only has to be complete. The right of return belongs to consumers (a purchase unrelated to business activity).
Complaints
If the product turns out to be faulty, you can make a claim under the guarantee or the statutory warranty. We handle claims without delay, at the latest within 14 working days of receiving the report together with the goods.
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GPSR data
Product information
This product is a component intended for further assembly or prototyping. It is not a finished product within the meaning of the product safety regulations.
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