When reading datasheets, you can note that almost all Renesas microcontrollers have Analog to Digital Converters, or ADCs, and some of them such as the RX62N has multiple ADCs as well as multiple channels per ADC. However, while possible to use ADCs without understanding what is going on behind the scenes, it’ll help in understanding some potential issues and to get the best performance if the process is more fully understood. ADCs allow microprocessors to convert analog signals into digital signals using the magnitude of the original signal, an important technology for sensors, dials, etc. The analog signal is sampled by the ADC, which uses tiny slices in time to record the amplitude and send it as a discrete, digital value to the microprocessor.
Physically, the ADC is relatively simple. The analog input hits the filter buffer which cleans up the analog signal. In its absence, one would require an incredibly fast clock to relay the changes to the signal. Together, the clock signal and smoother analog signal are sent to the sample block. There, the amplitude at each tick is recorded and sent to the comparator to be evaluated against a reference voltage. Then, the signal is read as a collection of highs and lows, creating a digital out code that can be read by the microprocessor.
Electronically, the setup of the ADC can be challenging for the inexperienced. Because of the many differences in microprocessors, it is necessary that the developer pays attention to the initialization process for their processor. Once the ADC peripheral has been activated, it’s important to establish a good sampling rate to preventing aliasing and other errors associated with samples being acquired at an incorrect pace.
Once the ADC has been initiated and timed and after a value has been obtained, the developer may need to fine-tune the signal. Depending on the complexity of the incoming signal, the tuning process can take a few minutes or a few hours. This tuning process is done by scaling the output values until they reflect real values. It is usually done in the registers, but hardware may be required in extreme cases.
ADCs are used for a variety of purposes. While they are an essential part of recording music, they are also used to digitize pixels, or to digitize values from instruments that read things like pH and temperature. The ability to turn a non-standard signal into usable information makes ADC’s a necessary tool for any developer, no matter what level they’re at.