You only need be concerned about these pins if you are using multiple This pin, we connect it permanently to +5V.Ī0, A1, and A2 are the address pins. The RESET pin is if you want the outputs all reset to 0. INT is the interrupt pin for the outputs.īeing that we are not going to use interrupts here, we just leave It connects to analog pin 4 on the arduino, which is the analog data line. It connects to analog pin 5 on the arduino, which is the analog clock pin. NC is Not Connected so we leave that pin unconnected (or floating). This completes the powering that's necessary for the Therefore, we can connect V DD to theĥV terminal of the arduino. The pinout of the MCP23008 is shown below. The datasheet for this chip can be found at the following link: It is a perfect addition to a microcontroller where more I/O ports are needed. The MCP23008 I/O port expander can be obtained for a little over $2. This circuit will fully demonstrate how to read input from I/O port expanders. When the pushbutton isn't pressed, its corresponding LED will be off. When a pushbutton is pressed, its corresponding LED will light up. In this circuit, we will connect 3 pushbuttons to 3 of the I/O ports and read whether the pushbutton is readingĪ HIGH voltage (in which it's pressed down) or a LOW voltage (in which it's unpressed). However, we haven't gone over a circuit on how to read data from input devices. We have shown already in previous circuits how to work with I/O ports to turn on output devices with So if you're running out of I/O ports on a microcontroller, it's a very useful way of getting additional In this project, we will show how to read input from input devices connected to an MCP230xx I/O portĮxpander connected to an arduino microcontroller.Īn I/O port expander is a chip that allows additional I/O ports to a microcontroller. How to Read Input from an MCP230xx I/O Port Expander Connected to an Arduino
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