“This is an SD-card module that allows you to write to and read from files on an SD card using a two-wire I2C interface.
It’s based on an ATtiny1614 and a few other components, and it’s compact enough to fit on a mini-breadboard.
I’ve frequently had a project where I wanted to write data to an SD card, or read from an SD card, but didn’t have enough I/O lines available to wire up the SPI SD card interface, or else the SPI lines were already in use, or else the processor I was using didn’t have enough RAM to run the SD library.
The ideal solution seemed to be an SD module with an I2C interface, but despite much searching on the web I couldn’t find one, so I decided to build one myself.
I initially thought of basing the circuit on the ATtiny841, like my earlier I2C GPS Module, but I underestimated the amount of RAM needed by the SD library, and the ATtiny814 only provides 512 bytes. I therefore switched to the 1‑series ATtiny1614 which provides 2 Kbytes.”