Read/Write MicroSD in 1-bit mode

There is no hardware support for SD 1-bit mode so only slow bit-bang would work. In SD bus mode CRC is required and this is also slow on the Arduino.

You can use bit-bang SPI with the SD.h library and SdFat.

For SD.h edit Sd2Card.h to enable software SPI and define the pins to be used.

Most MicroSD cards support SPI.