In this lab the student will build an analog-to-digital converter that transforms a reference voltage into a 6-bit digital number. The converted number will then be displayed on the LED display. The problem we face is that our current display is a single-digit display that can only display voltage levels between 0 and 9, a precision of only 3 bits. Since our ADC provides more than 3-bits of precision, we'll need to modify our LED display into a two-digit display.
A two-digit display can be built using the same basic principles employed in the previous lab. In particular, we propose using time in a controlled manner so that the MicroStamp11 first drives one digit of the display and then drives the other digit of the display. This approach is referred to as time-multiplexing. Time-multiplexing has the micro-controller switch back and forth between the multiple devices by using an electronic switch. In this lab the student will add an extra digit to the current display, use an electronic switch to alternately control each digit of the display, and then complete the hardware and software parts of the ADC. Finally, the student will test the ADC by verifying the correctness of the converted values for constant and time-varying reference voltages. For the last test, you will need to use another piece of electronic test equipment known as a function generator.