Adafruit Feather Basic Pro ATSAMD21 Cortex M0
By Adafruit Industries (2772)
MCM Part #83-17691
At the Feather HUZZAH's heart is an ESP8266 WiFi microcontroller clocked at 80 MHz and at 3.3V logic. This microcontroller contains a Tensilica chip core as well as a full WiFi stack. You can program the microcontroller using the Arduino IDE for an easy-to-run Internet of Things core. We wired up a high-quality SiLabs CP2104 USB-Serial chip that an upload code at a blistering 921600 baud for fast development time. It also has auto-reset so no noodling with pins and reset button pressings. The CP2104 has better driver support than the CH340 and can do very high speeds without stability issues.
To make it easy to use for portable projects, we added a connector for any of our 3.7V Lithium polymer batteries and built in battery charging. You don't need a battery, it will run just fine straight from the micro USB connector. But, if you do have a battery, you can take it on the go, then plug in the USB to recharge. The Feather will automatically switch over to USB power when its available.