A DIY Retrocomputer Programmed In Pure Rust

October 21, 2019 by Sharon Lin 17 Comments

Can you generate VGA and handle a PS/2 keyboard with a Cortex-M4 in Rust? That’s precisely what [theJPster] wanted to find out with Monotron, a 1980s style home computer programmed in pure Rust.

In order to run embedded Rust without a working operating system, some tools are necessary: an LLVM back-end for generating machine code, a target file for specifying memory sizes and other configs, and a pre-compiled libcore as a substitute for a compiler when running an operating system. Rust takes the place of C running on top of the board support package (BSP) and hardware abstraction layer (HAL), and peripheral access crates (PACs) that specify the hardware and allow the code to be portable across different chips.

The implementation generates a 800 x 600 VGA video signal at 60 Hz, displays text on a 48 character by 36 line display, displays color graphics using color lookup (stored in flash memory), and runs applications that take less than 24 KiB for all data. Monotron also generates 8-bit audio with PWM and sports a synthesizer that uses a three-channel wavetable allowing it to make sounds with square waves, sine waves, sawtooth waves, and create white noise.

So far, the Monotron has been able to work with an Atari joystick, a PS/2 keyboard, and has outputs to VGA, MIDI, SD card, and audio. Next up for the Monotron: writing a programming language (tentatively named Monotronian), adding support for Sega Megadrive pads, displaying sprites, and many more exciting developments.

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Navigating The Dark Side: Controlling Robots With Zero Radio Communication

October 20, 2019 by Sharon Lin 15 Comments

While autonomous robots have been the subject of some projects in the past, this particular project takes a swing at building a robot that can teach children about controls and robotics.

The idea is to mimic a space mission on the dark side of the moon, where radio contact is nearly impossible. The students learn to program and debug embedded devices and sensors, even before some of them have learned the alphabet!

The material for the challenge allows the microcontroller to be programmed in a simple Arduino program (Blink) as well as lower level languages like C++ or Java. The main hardware consists of an Arduino Uno R3-based rover controlled over WiFi by an ESP8266. The sensor data from the robot is gathered from an ultrasound distance sensor an a camera, as well as a SIM7000E GSM+GPS. Commands are polled from a server, sent via a web page and REST interface.

The rover responds to commands for directions, takes pictures, and scans its distance remotely. Some custom libraries are written for the serial communication and camera to account for spotty communication. The latest challenge expansion is a probe that pays attention to battery life and power consumption, challenging students to account for power usage during the robot’s lifetime.

Since the project’s conception, the rovers have already been used in schools, and we’re excited to see a new approach for younger students to learn controls and programming.

Beam Me Up To The PCB Space Ship

October 19, 2019 by Sharon Lin 15 Comments

This project would fit in perfectly with #BadgeLife if someone could figure out a way to hang it from their neck. Inspired by Star Trek’s Starship Enterprise, [bobricius] decided to design and assemble a miniature space ship PCB model, complete with 40 blinking LEDs controlled by an ATtiny85.

While the design uses 0603, 0802, 3014, 4014, and 0805 LEDs, some substitutions can be made since the smallest LEDs can be difficult to solder. The light effects include a green laser, plasma coils, a deflector with scrolling blue LEDs, and the main plate and bridge for the space ship.

The LEDs are controlled by charlieplexing, a technique for driving LED arrays with relatively few I/O pins, different from traditional multiplexing. Charlieplexing allows n pins to drive n²−n LEDs, while traditional multiplexing allows n pins to drive (n/2)² LEDs. (Here is the best explanation of Charlieplexing we’ve ever seen.)

Especially with the compiled firmware running on the MCU, the PCB model makes for an impressive display.

The only catch? Your Starship Enterprise can’t actually fly.

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Replacing The 3D Printer And Router: A Tool For Manufacturing Human-Scale Forms

October 18, 2019 by Sharon Lin 27 Comments

The purpose of Geometer becomes apparent when you realize its simplicity: [David Troetschel]’s project is to create an easily understandable design tool that encourages goal-oriented design. The kit comes with physical components and digital counterparts that can be combined in a modular way. They each have a specific geometry, which provide versatility while keeping manufacturing simple.

For the prototyping phase, small snap-on parts 3D printed on a Formlabs printer mimic the module components on a smaller scale. Once a design is conceived and the Geometer Grasshopper program finalizes the module arrangement necessary for the model, the larger pieces can be used as a mold for a concrete or hydrocal mold casting.

The present set of modules is in its seventh iteration, initially beginning as a senior thesis for [Troetschel]. Since then, the project itself has had an extensive prototyping phase in which the components have gone from being injection-molded to 3D printed.

The overall process for prototyping is faster than 3D printing and more cost-effective than sending to a third-party shop to build, which adds to the project’s goal of making manufacturing design more accessible. This is an interesting initiative to introduce a new way of making to the DIY community, and we’re curious to see this idea take off in makerspaces.

“The Thing”: A Homemade FPGA Board

October 17, 2019 by Sharon Lin 13 Comments

The Thing is an unassuming name for an ambitious project to build an FPGA board from easy to find components.

The project stems from an earlier build submitted to the 2018 Hackaday Prize by [Just4Fun] where two dev boards – an STM32-based Arduino and an Altera MAX II CPLD board – were combined with the Arduino used as a stimulus generator for the CPLD. This way, the Arduino IDE, interfaced through USB, can be used for programming the CPLD.

The Thing similarly uses the STM32 Arduino as a companion processor for the FPGA, with a 512KB SRAM and common I/O for GPIOs and a PS/2 keyboard for running HDL SOCs. It can also run Multicomp VHDL SOCs, a modular design that was made to run some older 8-bit CPUs made by [Grant Searle].

The FPGA (EP2C5T144C8N) uses the Quartus II IDE for configuration with a USB Blaster dongle through the JTAG or AS connector. The FPGA side controls a 4 digit seven segment LED display, four push buttons, 3 LEDs, a push button to clear all internal FFs (sampling rates), a push button to force a reboot (configuration reload), and a switch to force all pins to Hi-Z mode. Both an onboard 50MHz oscillator and connector for an external oscillator are also present on the FPGA side.

In one demo of the MP/M system capability of the board, The Thing was made to handle four concurrent users with one serial port connector to a PC and terminal emulator and the other serial ports connected to terminal emulators on VT100 boards routed through a dual-channel RS232 adapter board.

Both the Arduino and FPGA sides can also be used as standalone boards, but why use one when you can harness both boards together?

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The Smallest Homebrewed TTL CPU In The World

October 16, 2019 by Sharon Lin 16 Comments

This may very well be the smallest homemade TTL CPU we’ve ever seen. Measuring at one square inch, this tiny chip boasts 40 connections, an 8-bit databus, a 16-bit address bus, a 64 kB memory space, reset and clock inputs, and 5 V power lines.

TTL (transistor transistor logic) logic chips are pretty outdated today, but they do have all of the basics necessary for building a computer – logic gates, counters, buffers, and registers. The transistors perform both the logic and amplifying, as compared to resistor-transistor logic (RTL) and diode-transistor logic (DTL). In the 60s, when the technology was still fairly new, TTL ICs were commonly used in computers and industrial controls. Even after the advent of VLSI, TTL ICs were still being used for interfacing more densely integrated chips. Even so, most TTL chips tend to be on the bulkier side, which is what makes [roelh]’s project so unique. The entire PCB is hardly any larger than a coin.

On top of the hardware specs, [roelh] also implemented several useful software features: zero page addressing, load/store/compare instructions, stacks, conditioning branching, subroutine calls, and memory-mapped I/O. The registers are also in RAM, which has been implemented in microprocessors in the past (see TMS9900) for speed considerations, but in this case was implemented for size constraints.

An ALU was also left out of the design in order to constrain its size, leaving only 8 ICs on either side of the 2-layer PCB.

Microprograms are stored in Flash memory and can be programmed with a Raspberry Pi. by saving the Assembly code to a memory card and downloading the assembled binary code. Once the Raspberry Pi is connected to the development board, you can burn the binary code onto the Flash memory of the board using a Python script. An online Javascript editor also exists for assembling the Assembly code for the chip and simulating the CPU.

There is currently a development board made for the CPU, which includes six seven-segment displays and an I/O connector for running a digital clock and other applications. [roelh] has since built a retro TTL computer around the chip, which reintroduces the ALU and includes address registers, 256 KB of RAM, VGA video, PS/2 keyboard port, a sound system, and I/O pins. It’s a really exciting project that’s seriously pushing the constraints of retro computing.

A (Mostly) 3D Printed Servo/Gear Reduction

October 14, 2019 by Sharon Lin 5 Comments

This servo/gear reduction was assembled with almost all 3D-printed parts. Apart from a brushed 36 V DC-motor, a stainless steel shaft, and screws for holding the servo together, the only other non-printed part is the BTS7960B motor driver.

Some interesting stats about the plastic servo – its stall torque is about 55 kg/cm, reaching a peak current draw of 18 A when using a 6s LiPo battery outputting 22-24 V. The shaft rotates using two 20 mm holes and lubrication. (Ball bearings were originally in the design, but they didn’t arrive on time for the assembly.)

The holes of the gears are 6.2 mm in diameter in order to fit around the shaft, although some care is taken to sand or fill the opening depending on the quality of the 3D print.

This isn’t [Brian Brocken]’s only attempt at 3D-printing gears. He’s also built several crawling robots, a turntable, and a wind up car made entirely from acrylic. The .stl files for the project are all available online for anyone looking to make their own 3D-printed servo gears.

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