PCF8591 ADC/DAC  pcf8591 Module http://wiki.sunfounder.cc/index.php?title=PCF8591_8-bit_A/D_and_D/A_converter_Module pcf8591 Datasheet https://www.sunfounder.com/learn/sensor-kit-v2-0-for-raspberry-pi-b-plus/lesson-13-pcf8591-sensor-kit-v2-0-for-b-plus.html .END