Intro: MegaMUX - 32 Channel Multiplexer Tutorial
Often when I have an idea for a new project, it will involve some components or circuitry that I have not used before. To be safe, I will sometimes design a smaller "test" board with just that component or circuit to test it out before I design the larger project. This is where the MegaMUX comes from. I wanted to test out the ADG732 multiplexer which is a 32 channel MUX. This means you can connect one output from the MUX, and select 32 other IO to connect to it. In this project I will show you how to connect the MegaMUX to an Arduino, and give you an idea of what you can do with it.
Step 1: Watch the Video!
The video has a lot of info, and I go through how the Arduino programs work in detail. Enjoy!
Step 2: Get the Parts, Components, and Tools.
Step 3: Solder on ADG732, Caps, and Header Pins
Since I'm only making one or two of these, I'm just using my soldering iron to place the chip. Use whatever method you're comfortable with.
I soldered on the header pins so they could be placed in the breadboard with the IO right angle pins sticking out the back.
Step 4: Connect It to an Arduino
If you would like to use my demo programs, connect the IO as shown below. Left is the MegaMUX, right is the Arduino.
- VCC -> 3.3V
- GND -> GND
- A0 -> GPIO13
- A1 -> GPIO12
- A2 -> GPIO11
- A3 -> GPIO10
- A4 -> GPIO9
- CS -> GPIO8
- WR -> GPIO7
- EN -> GPIO6
- IO -> A0
Step 5: Testing Output Program
If you would like to use the program to test outputs on the MegaMUX, connect each IO pin of the MUX to an LED. Connect a suitable resistor between IO on the MUX and A0 on the Arduino.
Download my Arduino Program and upload it.
If everything is correct the LEDs should be lighting up one at a time cycling through all of the pins.
Step 6: Testing Analog Input Program
If you want to use your MUX as an analog input, I used photoresistors as a demonstration. The photoresistors are added on one side of the mux(IO 1 to 16) instead of the LEDs. I setup the output pin to be a voltage divider. Each time the pin is switched the next photoresistor will become the other half of the voltage divider and report to the analog pin of the Arduino.
Download the INPUT program and upload.
The program will cycle through the photoresistors, allowing you to sample from each one. You can see this if you open the "Serial Plotter" in the Arduino IDE.
If you haven't yet, watch the YouTube video on details how the program works.
Step 7: Learn Something New
Now that you have setup your MegaMUX and played around with the Arduino programs, try and come up with your own use for the board. This basic idea is that this expands the GPIO on the Arduino. Leave a comment on what you used it for!
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