This is a simple project to build a small timer using a 8x8 LED matrix driven by a ATTiny85 microcontroller. Each LED is a minute but I'm still searching for an original way to display the time.
The code to switch on and off LEDs is inspired by the Adafruit library available in this repo.
The main functions are:
setPixel(x, y)to switch ON one LED at coordinates (x,y).unsetPixel(x, y)to switch OFF one LED at coordinates (x,y).display()to trigger a display.
There are also several functions to initialise the chip driving the LED, switch on the display and set the brightness.
The LED matrix I'm using is the Adafruit 0.7''. You can buy it here in UK. The LED matrix is driven by a ht16k33 using I2C commands (datasheet).
For the gory details of the I2C communications I use a software implementation (in Assembler) from this library from Peter Fleury. The ATTIny doesn't have an I2C (a.k.a. TWI) built-in hardware.
The makefile is also from the same library.
At the moment the LED matrix and the microcontroller are on a mini breadboard and powered by a fairly big battery. But at some point I want to change for a smaller battery and 3D print a tiny case.
This project uses avrdude and avr-gcc. The makefile is tailored for an ATTiny running at 1 Mhz flashed by a usbtiny programmer.
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Clone the repo:
git cloneand go into the directory. -
Connect the LED matrix to the microcontroller using the I2C clock and data pins. I used this really nice pin-out diagram.
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Flash the microcontroller using:
make program