Etsy-Ghost-OLED
Small single-weekend project to display an animated pixel-art ghost on a transparent OLED.
Hardware
- ATTiny85
- DECA MAX10 FPGA
- NPN transistors, resistors, throw switches
- Male-male, male-female, female-female jumpers
- Digilent Analog Discovery Oscilloscope (debug only)
Software
The final software base is under sw/app.c
The application is straightforward, it uses a timer interrupt to draw animation frames by sending commands and data over a bit-banged SPI bus to the transparent OLED with SSD1309 drver. Some of the features of the SSD1309 just did not work for me, like horizontal left/right scrolling, so I had to emulate them in my software design.
Code is compiled using avr-gcc. An objdump and objcopy are performed, followed by some hex editor maniupulation to obtain a pure hex file of the output binary.
Programming the ATTiny
This was somewhat a PITA. In my mind I could purchase the ATTiny board, plug in a USB cable, and see the ATTiny in the device manager / Linux filesystem. Not!
Instead, the easiest way to program the board I bought was over SPI, so I created a small FPGA design to bridge the Quartus System-Console (JTAG) directly to the ATTiny.
The hex file from before was then passed through a Python script to form a series of writes within a TCL script to the ATTiny. By holding reset low with a switch on the DECA board and running the script in the System-Console, the ATTiny flash would get loaded with the compiled code object. Releasing reset would then run the design.
Bitmaps
The ghost animation was converted saved manually as monochrome bitmaps. These were then processed into a compressed custom format so that they could be loaded directly into the ATTiny flash memory. The C-code can then loop through the arrays and display them on the screen.
Building
# create header files from bitmaps
cd oled
make
# build software
cd sw
make
# create fpga design
cd fpga
make
# load onto hardware
make prog
# open system-console
make console
# load ATTiny flash (within system-console)
source flash.tcl