A while back, [Jacob] played around with a player piano. After feeding a roll into the machine and trying to figure out how a fifty year old machine using hundred year old technology can replicate a skilled pianist, he decided to take a crack at decoding piano rolls for himself. He came up with a clever way of doing it over Christmas break, using a camera and a few bits of OpenCV.
The old-school mechanics of a player piano use a bellows and valve system to suck air through dozens of holes, making the action hit a string whenever a hole is present in the piano roll. To bring this mechanism into the modern age, [Jacob] pointed a video camera at the active part of the piano roll and used OpenCV to translate holes in a piece of paper to a MIDI file.
The synthesized version sounds just as good as the original paper scroll-based version, as seen in the video after the break. There are a few sync issues in the video and the resulting MIDI file isn’t in the right key, but that’s easily fixed by anyone willing to replicate this project.
Continue reading “Reading piano rolls without a player piano”
The TRS-80 Model 100 was an amazing piece of kit when it was released. Able to run for a week with just four AA batteries and smaller than some laptops today, this portable version of the TRS-80 saw action with war correspondents covering the Falklands invasion. A pedigree a MacBook Pro will never be able to live up to, it seems.
[Hudson] picked up a non-functioning Model 100 with the express goal of replacing the 30-year-old electronics inside with an updated motherboard – and also pull up our retro site in the process. Armed with a Teensy++, [Hudson] pried open his ancient computer and set to work interfacing the display and keyboard to his AVR dev board.
The LCD display in the Model 100 has a resolution of 240×64, driven by ten Hitachi HD44102 display drivers. Each of these display drivers are responsible for the pixels in a 50×32 rectangle on the screen and are interfaced with a 30-bit wide bus consisting of chip select lines, and 8-bit data bus, and a few other random control lines. [Hudson] plugged this 30 pin header into his Teensy++ and after a bit of ingenuity regarding the strange electrical requirements of the LCD, was able to control every pixel on this 30-year-old display.
The next order of business was interfacing the keyboard with a modern microcontroller. The keyboard is laid out in a normal matrix, but with a few oddities: characters like ~, |, and curly brackets aren’t present on the Model 100. After working these problems out, [Hudson] set to work on a VT100 terminal emulator. This allowed him to run vi and lynx, enabling him to pull up the Hackaday retro site in a wonderful forty-column text mode.
Future improvements to this redesign include designing a proper PCB to replace the current protoboard design. The original Model 100 included a text editor and programming language, and adding a Forth implementation isn’t out of [Hudson]’s grasp. It’s an awesome build, and an excellent improvement that will allow [Hudson]’s Trash-80 to see another 30 years of use.