Adafruit featherwing add ons for all feather boards adafruit 3028 the adafruit ds3231 i2c precision real time clock featherwings are extremely accurate real time clocks rtc that feature temperature controlled crystal oscillators tcxo with the crystal inside the main chip and a temperature sensor right next to it clock ticks can be dropped or added to compensate for drift caused by temperature changes the chip is claimed to be accurate to plusmn2ppm which is equivalent to one second e