This is the Adalogger FeatherWing: it adds both a battery-backed Real Time Clock and micro SD card storage to any Feather main board.
This FeatherWing will make it real easy to add datalogging to any of our existing Feathers. You get both an I2C real time clock (PCF8523) with 32KHz crystal and battery backup, and a microSD socket that connects to the SPI port pins (+ extra pin for CS). Tested and works great with any of our Feathers, based on ATmega32u4, ATSAMD21, or ESP8266.
We recommend the Arduino's default SD library to talk to the microSD card socket. On ESP8266, the SD CS pin is on GPIO 15, on Atmel M0 or 32u4 it's on GPIO 10. You can cut the trace to the default pin and change this to any pin. To use the RTC, use Adafrutis RTClib library. If you need a precision RTC, check out the DS3231 FeatherWing
Does not come with a micro SD card. A CR1220 coin cell is required to use the RTC battery-backup capabilities! We don't include one by default, to make shipping easier for those abroad, but you can use any CR1220 you have handy. If you're not using the RTC part of the featherwing, a battery is not required.