Library ADC MCP33121
You don't really need a library for that chip. You just do a pair of SPI transfers with the CS pin low.
For example:
digitalWrite(pinCS, LOW);
uint8_t msb = SPI.transfer(0xFF);
uint8_t lsb = SPI.transfer(0xFF);
digitalWrite(pinCS, HIGH);

uint16_t val = (((uint16_t)msb &lt;&lt; 8) | lsb);
val = val &gt;&gt; 2; // For 14 bit devices shift it twice. For 12 bit do it 4 times.