For the homebrew computer, I will need to implement SPI and I2C support to allow the FPGA to communicate with the LCD screen and ADC. To get an idea of how to go about this, I turned to tutorials uploaded on Youtube. But before getting in deep, I started by learning a simpler protocol, asynchronous serial communication.
Here are some additional resources I’ve come across for learning shaders.
Book of Shaders →
Great resource because it starts from the absolute basics and builds up, rather than skipping to all the fancy stuff. Emphasis is placed on understanding the fundamentals and developing an intuitive understanding of how things work.
Good introduction to lighting. The tutorials are based on OpenGL but can be adapted to Three.js (which is what I used to follow along). Here’s a toon shader I made from one of the lessons (click image for animation):
Shader School →
I think it’s a bit useless to work through this one if you do not have prior exposure to GLSL. But once you do, it’s an awesome series. There’s even a section that touches on using the GPU for general purpose computing.
WebGL Workshop →
It is intended to be taken after Shader School. The course teaches you how WebGL (based on OpenGL) works. Basically all the stuff libraries like Three.js do on your behalf. Even if you don’t intend to write your applications using raw WebGL it is useful to understand what is happening behind the scenes.
A neat trick I learned from the course was
discard. You can either render a pixel (default) or specify that it be ‘discarded’ (i.e. skipped). Here is a slicing effect I made using this (click image for animation):
Interactive 3D Graphics →
Though not strictly a shader focused course, it covers so many fundamental concepts with regards to 3D graphics that skipping it would be doing yourself a disservice. The course is taught using Three.js and touches on pretty much everything you need to know about how 3D computer graphics work and how to create them.
I chose to use VHDL to program the FPGA because it is closer to a schematic representation than Verilog. Verilog seems (to me) like learning a new programming language whereas VHDL is more like describing the circuit.
For example, take the construction of a full adder. Here is a video of the structure generated by my code below:
I bought an analog to digital converter for the computer.
The FPGA can only process digital signals (on or off, 3.3V or 0V) but the touch screen outputs analog signals (values ranging from 3.3V to 0V each representing a relative position).
It was my first time soldering (the header pins). As you can see, all the flux was used.
I roughed out the design using Inkscape. (Because unlike Photoshop or Gimp, you can easily move and resize shapes around after creating them).
fillColor. The color scheme is based on this palette with tweaks here and there.
When used with the Arduino SD Library, one can easily read, write, create, and remove files (and directories).
The SD card solution is also very convenient! You can plug the SD card into any regular computer (or phone) and copy onto it any programs you want to run on the Hack Computer (for example these games on Github). (Think game cartridge or USB thumb drive). Similarly, if you write a program and save it onto the SD card when using the Hack Computer, you can then open it up later on any other computer (or phone).
I got it for $20 on eBay and the kit came with a (knockoff) USB Blaster for programming. The idea to use the board came from Charles Cole’s hardware setup of his homebrew Z-Machine. The price is great and I love that it only has the bare minimum components on it.
I worked through this excellent getting started guide by Trey Dahlberg on Youtube and everything seems to be running well.
- Altera Cyclone II EP2C5T144C8
- 50MHz clock
Update (January 18, 2017):
I recently came across the Multicomp project by Grant Searle. In it he uses this development board and consequentially has a ton of really helpful information on the board and some of the things it’s capable of. The project is described by Hackaday as a ‘pick and mix retrocomputer’ which allows you to use the FPGA as a Z80, 6502, 6800 or whatever CPU mashup you feel inspired to. His project also describes in detail interfacing with various devices including SRAM, SD cards, VGA, composite video, PS/2, USB - basically I found the holy grail! Check out the project page to learn more about the board, and maybe even build a mix and match computer of your own.
Note: if you use this development board, make sure to desolder the four zero ohm resistors as explained in Grant’s project page.
I got it for $10 compared to Adafruit’s price of $40. I came across the screen through this awesome video by Charles Cole where he walks through his FPGA implementation of a Z-Machine. I also bought the Altera mini dev board he recommends ($20 which is a steal) but that’s another post.
My gameplan is
- To first get it working on Arduino (since there is information available online on how to do so).
- Once it works on Arduino, convert the relevant files (driver, graphics) from C, Python, or whichever language is used to Hack Computer’s high level language.
- Then change a few things here and there on the Hack Computer so that it outputs for the LCD screen instead of Tkinter.
Part 1) Getting the screen to work
Particles are cool! Example,
I had this idea back in 2014 of getting the points from premade 3D models (similar to the video above), and using them to do fancy animations in Threejs. Then I hit a knowledge wall and shelved it. Until today…