seeed studio Seeeduino XIAO Board Based on SAMD21Cortex M0+, 100% Compatible with Arduino IDE, Mounted breadboard… Price: $21.99 (as of 25/11/2020 05:08 PST- Details)

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【Powerful CPU] Seeeduino XIAO board carries ARM Cortex-M0 + 32bit 48MHz microcontroller (SAMD21G18) and low power consumption. The clock frequency is 48MHz, which is three times that of Arduino Uno and Arduino Nano. In addition, Seeeduino XIAO is equipped with 256KB flash memory and 32KB SRAM. We have prepared a wiki so that customers can get started quickly. (Wiki:
[Flexible Compatibility] Seeeduino XIAO development board is Fully compatible with the Arduino IDE ,you can easily develop some Micro projects with the help of the large and comprehensive Arduino library. As it has a 2.54mm pin pitch, it is a replacement for Arduino microcontroller that can be used even when inserted into a breadboard.