Serial Peripheral Interface (SPI) is a synchronous serial communication whose data or signal transmission involves Chip Select (CS) or Slave Select (SS) pins, Serial Clock (SCK), Master Out Slave In (MOSI), and Master In Slave Out (MISO). In the Arduino Uno, there are four pins that allow Arduino Uno to perform SPI communication. In this research, SPI communication is implemented to expand the output of the Arduino Uno by using the features of the MCP23S17 IC so that the Arduino Uno, which initially has 20 output pins, can expand to 36 output pins.The results of the research show that the Arduino Uno manages to control 36 output pins. 16 output pins from the MCP23S17, 16 output pins from the Arduino Uno, and 4 pins are used for the SPI communication line. The results of this study also show the form of the SPI communication signal from Arduino Uno in declaring 21 registers on MCP23S17, declaring the MCP23S17 pin register as output, and implementing the output using LEDs.

Arduino Uno is a minimum system board that use atmega 328p as a microcontroller IC (Integrated Circuit). Arduino Uno has 20 output pins. The running out of the pins owned by the Arduino Uno makes it cannot control many LCD, such as 3 LCDs that require 21 pins. With the lack of the Arduino Uno, this study is focusing on expand output pin of Arduino Uno so that it has 32 additional pins by making use of internal SPI communication. This expansion on the Arduino Uno uses 2 MCP23S17. MCP23S17 one to control LCD 1 and LCD 2 while MCP23S17 two to control LCD 3 and LCD 4. The method used in this study is a quantitative method. Data register that used to support SPI communication in this study was obtained from the MCP23S17 datasheet. The results of this study show a table of register data SPI set address that can be used to control the expansion pin on MCP23S17 and pictures of 4 LCD control display.

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In the world of education, a process of experience is obtained as a result of learning. To improve the quality and creativity in their learning, serious efforts are needed in creating tools as learning media. By making a signal generator PQRST tool from the research this time, students are able to know the PQRST signal form. The results of this study are the tools successfully created by producing signals with the form of PQSRT signals. From the results of the filter testing, HPF with cutoff frequency of 250 Hz will change the shape of the PQRST signal. This is caused by HPF 400 Hz cutoff frequency value is greater than the PQRST 296 Hz signal frequency. This also applies to LPF, LPF 500 Hz cutoff frequency value is smaller than the PQRST 593 Hz signal frequency so that the PQRST signal will be further away from the original form. in testing the BPF, the PQRST frequency of 296 Hz will not change due to the range of cutoff frequency values is 100 Hz to 500 Hz. After that, this study got results of student responses with an average of 4.2 out of 5.

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