OSPi has an on-board 4-channel ADC (PCF8591) that you can use to read analog sensor values. Although the firmware doesn’t have built-in support to read the ADC, there are plenty of C++, Python, or command line script code you can find to read the ADC. For details, check the OSPi user manual page 7:
http://rayshobby.net/docs/ospi14_manual.pdf