Adafruit Adalogger FeatherWing

RTC + SD-card Add-on, for all Feather boards and more!


This FeatherWing will make it real easy to add datalogging to any of the 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). If you're not using the RTC part of the FeatherWing, a battery is not required.

Adafruit has tested it and the Adalogger works great with any of the Feathers, based on:

  • ATmega32u4
  • ATmega328P
  • ATSAMD21
  • ATSAMD51
  • nRF52
  • Teensy
  • ESP32
  • ESP8266
You don't have to use it in combination with a Feather board any MCU board with the same GPIO pins can be used!


Pinout

Even though every pin from the Feather is doubled up with an inner header not all of the pins are actually used!


Power pins

On the bottom row, the 3.3V (second from left) and GND (fourth from left) pin are used to power the SD card and RTC (to take a load off the coin cell battery when main power is available).


RTC & I²C pins

In the top right, SDA (rightmost) and SCL (to the left of SDA) are used to talk to the RTC chip.

  • SCL - I²C clock pin, connect to your microcontrollers I²C clock line. This pin has a 10K pullup resistor to 3.3V
  • SDA - I²C data pin, connect to your microcontrollers I²C data line. This pin has a 10K pullup resistor to 3.3V

These pins are in the same location on every Feather.

There's also a breakout for INT which is the output pin from the RTC. It can be used as an interrupt output or it could also be used to generate a square wave. Note that this pin is open drain - you must enable the internal pullup on whatever digital pin it is connected to!


SD & SPI pins

Starting from the left you've got:

  • SPI Clock (SCK) - output from feather to wing
  • SPI Master Out Slave In (MOSI) - output from feather to wing
  • SPI Master In Slave Out (MISO) - input from wing to feather
These pins are in the same location on every Feather. They are used for communicating with the SD card. When the SD card is not inserted, these pins are completely free. MISO is tri-stated whenever the SD CS pin is pulled high.


SDCS Line

The SDCS pin is the chip select line.

  • On ESP8266, the SD CS pin is on GPIO 15
  • On ESP32 it's GPIO 33
  • On WICED it's GPIO PB5
  • On the nRF52832 it's GPIO 11
  • On Atmel M0, M4, 328p or 32u4 it's on GPIO 10
  • On Teensy 3.x it's on GPIO 10
You can cut the trace to the default pin and change this to any pin by soldering a wire to any available pad.


Links