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Mounted and running


I love working with microcontrollers, and have an interest in low-power things. To get some more practice working with atmega328's I'm going to build a small LED matrix that will label my member storage at the shop.

To begin I'll write the code as an Arduino sketch, then pivot pieces to more traditional C firmware as I learn about them.

Parts List

  • Sure Electronics 32x8 LED Matrix
    • I'm pretty sure the LED boards on this thing can handle both red and green, but it's not wired up to work :-/
    • Can output 16 levels of PWM based brightness. Need to investigate library to see if individual pixels can be set.
    • Need to look at what can be merged between the Adafruit library and the one I'm using.
  • HC SR501 PIR sensor
    • Detects human activity by the infrared we emit.
    • Outputs 3.3V high for detected movement. Ground for standby.
    • More information
  • ATmega328P
  • Breadboarding supplies
    • 16MHz crystal
    • 2x 22pF Capacitors


Remember above where I said I thought the LED matrix could support Red AND Green? Well, it can. The HT1632C on the other hand can only support one set of 32x8 or 24x16 LEDs. On Sure Electronic's BiColor displays, there are two HT1632C's for every array of LEDs. Which means that I think this display can be upgrayeded to BiColor by piggybacking on another HT1632 and splicing it onto the back of the PCB.


Sure Electronics 32x8 Red 3MM Board

SureElec's page for the board (different sku now?)

XSM-D1088ARG LED Matrix Datasheet

HT1632C Datasheet


Gauravmm HT1632 Github


nongnu AVR interrupts guide interrupts&timers guide

Arduino interrupts guide

Another Arduino interrupts guide

Low Power Mode

Arduino Sleep Code


loop() and setup() vs main()

Arduino/ATmega pinout