This article introduces the ESP32 and SAM-D21 microcontroller board to learn how to use ADC (Analog to Digital Converter) and DAC (Digital to Analog Converter) instruction by connecting the DAC pin to ADC as shown in Figures 1 (Connect A0 to A1 of Board SAM-D21 ) and 2 (Connect Pin GPIO26 to GPIO36 of ESP32) to send data to DAC and have ADC read it back. Then send the results out to the serial port for display with the Serial Plotter, which is an example program to send 3 types of data, which is a zigzag graph, triangular graph and waveform graph from the sinusoidal function