OpenAmiga600RamExpansion V1

The HB6809 is a mini ITX form factor 6809 based open expansion computer. there are four expansion slots available which are pre-addressed in to 4K sections, providing enough space to build fairly versatile modules. Currently there is a bare bones serial module but more modules are in the works for sound, traditional HID devices like keyboards / mice / controllers, and graphics. You can download the full project files schematics and more on the GitHub or Hackaday.io sites for this project.The serial expansion card is also available as a shared project as well, though the schematics are simple enough the serial controller could be built on the prototyping area of the main PCB as well.

To create this project I was inspired by the ability to synthesize digital circuits using the Verilog and System Verilog languages.From my own experience, I would like to note that many industrial controllers or programmable relays use “Functional block diagram” semantics as a description of control system algorithms. Naturally, the experience gained with this board can be easily used in industry to obtain reliable, efficient and inexpensive solutions.But and not only in industry.Next in the package Examples there are examples of synthesized circuits. I am grateful to everyone who has read up to this point. For questions and suggestions, write to the email address: daineko.a32@mail.ru P.S. All the best and fresh cookies!

In this article "How to Controls WS2812B Using ESP-01 Arduino (ESP8266)". I made a custom module for the WS2812B LED using the ESP-01. With this module I can make various creations using the WS2812B LED. Among them are RGB LED Strip, RGB LED Animation and RGB Matrix. And in this article I will create an RGB Light Pocket using the WS2812B LED Matrix. I will use this LED for photography lighting. What I hope is, this LED can give a unique impression from the photos I take.Component and Material Components for the ESP-01 modul :4* SMD Resitor 10K Ohm2* SMD Capacitor 10uF1* Regulator 3V32* 1x4 Female Header1* ESP-01Material :1* Modul WS2812B esp-011* Modul Charger Battery1* 8x8 Martik LED WS2812B1* Battery 186501* Battery Holder1* Switch ON/OFF2* Push Button4* 3mm Screw4* 3mm Mur2* 1cm Spacer2* 0.5cm SpacerCableDouble tapePCB HoleBox DesignThe box for this LED pocket I made using a 3D printer. The material I use is PLA. You can see the Box design below. I designed this box on onshape.com.WS2812B ESP01 Module Schematic and LayoutThis is the basic schematic for using the ESP-01 module. The 10K resistor is used as a Pull UP in some of the PINs for the ESP-01 configuration. There are 2 buttons, namely the reset button and the Flash button which are connected to the GPIO0 PIN. With this button I can change the ESP-01 mode to Programing mode or boot mode. The 5P Male header is used to program the ESP-01 by connecting it to USB to Serial. 3P Male Header is used for additional PIN if needed. 2P T-Block for Power supply. 3P T-Block for WA2812 LED. IC 1117 is used to lower the voltage from 5V to 3V3 to supply the ESP-01. You can see the layout and schematic in the image above. And below you can download the original Schematic and Layout file. You are free to use or change the files that I provide.AssemblyTo simplify the assembly process, I removed the connector component on the WS2812B module. for installation I directly solder to the PCB. And here is the installation scheme. You can follow this scheme to assemble all the materialsSoftwareThe software that I made is quite simple. so there are several colors that I provide. To change the color simply press the mode button once. You can add any other color you want, just by modifying a few lines of code.Video

DESCRIPTIONI was fascinated by this type of gearbox and always wanted to make one. This type of gearbox is one of the most used in industrial robots. This type of gearbox only has a single reduction (in this case 2 because of the belt reduction) with a very high reduction ratio. Because of the single stage reduction there's almost no tolerance/play between input and output shaft. Conventional gearboxes use more gears to achieve the same reduction ratio, the tolerances between the gears add up resulting in greater tolerances/play between the input and output shaft.Video:Thank you to PCBWay for sponsoring this project. More info about them can be found in the speed controller section further down.Here are some specifications of the gearbox:Max tested torque at 12V: 41.3kg*cm or 4N*mReduction ratios:Circular spline teeth amount: 50 teethFlex spline teeth amount: 48 teethSmall GT2 pulley: 16 teethBig GT2 pulley: 36 teethReduction ratio strain wave gear: (48 - 50)/48 = -0.04161/0.0416 = 24.038Reduction ratio = 24.038:1Reduction ratio belt drive: 36/16= 2.25Reduction ratio = 2.25:1Total reduction ratio = 54.0855:1Electrical specifications:Motor type: 775 brushed motor (see parts list)Motor Voltage: 0-24VDCIdle power consumption at 12V: 10WPCB rated voltage: 12VDCPCB rated voltage with jumpers for Arduino power supply removed and replaced by a separate DC-DC converter module: 24VDCWorking principleA strain wave gearbox has 3 main components:-Wave generator-Flex spline-Circular splineStrain wave gear working principle. Picture source: Wikipedia.orgThe wave generator (green) generally is the input side of the gearbox and has the highest RPM. The wave generator is being used to deform the flex spline and make the teeth interlock with the fixed outer circular spline (blue). The flex spline (red) is generally the output of the gearbox and has the lowest RPM. One full rotation of the wave generator will move the flex spline 2 teeth in the opposite direction.Circular, flex spline and wave generator designThe design of the teeth for the circular and flex spline turned out to be a little harder then expected. I originally wanted to use double helical gear generator to create the teeth but the teeth ended up interlocking over the complete circumference of the splines, even with a 4 teeth difference between them. Then I tried regular spur gears but these gave the same problems as the double helical teeth. It turns out strain wave gears don't use regular teeth but a much shorter and more straight tooth profile.After the tooth profile was figured out I 3D-printed a first test with a flex spline in PLA. This initially seemed to work pretty good but after a few minutes of turning the flex spline made a few weird noises and pretty much exploded. So this was not going to work. Then I tried printing it TPU filament (flexible filament) which worked a lot better. The dimensions and structure of the flex spline and wave generator needed to be modified a bit in order prevent the flex spline from slipping inside the housing (tighter tolerances needed).The wave generator originally used 4 bearings to push the flex spline in the outer circular spline but when I switched the material of the flex spline from PLA to TPU I changed this number to 6 to make the contact area bigger and prevent slipping of the flex spline.PerformanceOriginally the limiting factor of the gearbox was belt reduction used to drive the wave generator. After changing out the plexiglass lid for a 3D-printed lid and adding an extra motor spacer between the case and motor this issue was resolved. The limiting factor now is the motor itself in combination with the reduction ratio of 54:1. The strain wave gearbox has a stall torque of around 41.3kg*cm or 4N*m.Speed controllerFirst of all a big thank you to PCBWay for sponsoring this project. Due a price drop in raw materials, PCBWay can now provide PCB's at a reduced price. Use my referral link to get a 5$ discount when you sing up as a new user: https://www.pcbway.com/setinvite.aspx?inviteid=586251To control the speed and direction of the motor I designed a custom Arduino Nano based PCB. The PCB features a reverse polarity circuit, a voltage divider to measure the supply voltage, some resistors for LEDs and some header pins to connect the PCB to the IBT2 motor driver.The gerber file for the PCB can be found in the files section on this page.

Hello,This board has been tested on the Amiga 500 port-1 connected with a PS/2 mouse and standard joystick. (Pressing fire button activates joystick, pressing any button on mouse activates mouse.)If you have a PIC16F628(A) and a PIC-Programmer, you can make your own Amiga PS/2 mouse converter adapter, with this circuit-board easily.REV.3 also contains an input for standart 9 pin Amiga joystick. This dual-input adapter acts like a Y-Cable that can be used to simultaneously plug both PS/2 compatible mouse and 9 pin standart Amiga joystick to your Amiga computer. Switching between joystick and mouse is easy; Pressing fire button activates joystick, pressing any button on mouse activates mouse.This Amiga PS/2 Mouse Converter adapter supports; three mouse buttons, most of optical PS/2 mice and some of USB mice (supporting PS/2 communication protocols) (with a simple and cheap USB to PS/2 converter.)You need to download .HEX file and program it in to PIC16F628(A), from this link,https://archive.org/download/amiga-ps-2-mouse-pic-16-f-628/AMIGA_PS2_MOUSE_PIC16F628.zipCOMPONENTS:PIC16F628A or PIC16F628DIP18 IC SOCKETDB9F D-SUB 9 PIN SOLDER TYPE FEMALE CONNECTOR - You can remove the metal cover if necessary (for A600)DB9M D-SUB 9 PIN SOLDER TYPE MALE CONNECTOR6PIN RIGHT ANGLE PS/2 FEMALE PCB TYPE MINI DIN CONNECTOR100nf CAPACITORIn order to protect your electronical devices, always turn off your Amiga before connecting or disconnecting the cables or any other device.Gerber files can be changed at any time. Before paying for the PCBs, be sure to update your orders!Use this PCB at your own risk !Have funThank you.

This is the best version of my 18 key keyboard I have built so far. I peak at 100wpm on this. Mainly though it is the feeling of an almost total lack of effort needed to type on it that is the most striking. Pictures and information on the board and layout can be seen here:Layout: https://www.youtube.com/watch?v=5RN_4PQ0j1ABoard: https://www.youtube.com/watch?v=0d8mjsVgk1k

Watch Full TutorialToday we will take a look over what is FOC control, create an awesome PCB and control a triple phase brushless motor with it at very low speeds and precise movement. FOC is a very common and useful method of controlling brushless motors and is used a lot in robotics. I want to explain to you how it works, how the PCB is made and show you the code and an example for an open loop control and then a closed loop control using a magnetic encoder which is also very important. As always, you can get from below the PCB files, the schematic and everything you need to make the same project. So guys, let’s get started.Full part list here.Today we don’t make a normal brushless motor controller or so-called ESC. We make a controller that is called FOC and stands for field-oriented control and for this project I’ve made a PCB that you could download from below and order it at PCBWAY as always, and make the same project. It has everything you need and it has screws for the motor, a smaller PCB for the magnetic encoder which is very important, it also has the triple phase driver and an ATMEGA328 microcontroller and a bunch of inputs and outputs. So get my files and go to PCBWAY.com and click the quote now button. Insert the PCB size and select the amount and solder mask color. Click save to cart and on the next page upload my GERBER files. Place the order in just a couple of minutes and receive perfect PCBs. They look amazing with the red solder mask. I’ve made the design in such a way that later we can cut the tiny part and place it over the big PCB.

Purpose of the projectMy project is about preventing old hardware from being abandoned. I decided to make it because original Memory Card for PS1 are not being manufactured anymore. Used one are often very expensive (and in unknown conditions) while cheap import clones do not work nearly as well.With PicoMemcard instead, you can build a USB-compatible MemoryCard with unmatched performance! Best of all? It's cheaper than buying a used original Memory Card!FeaturesAble to faithfully simulate PSX Memory CardUSB connection to import/export savesAllows to copy saves to/from any other memory card (using original PSX file manager)Allows to play burned CDs (thanks to FreePSXBoot)Cheaper than an original memory cardCan store hudreds of memory card imagesHow it worksIt works by using the PIO (Programmable I/O) funcitonality of the Pico to intercept the protocol used by the PSX to communicate with memory cards. By using a carfully crafted piece of software that I developed, it's possible to trick the PSX into beliving a real memory card is plugged in and simulate it using only a Raspberry Pi Pico and a hardware interface to the PSX.As for the hardware interface, it's possible to use a broken controller cord, a broken memory card or the PCB I personally designed for this purpose. It's also possible to 3D-print a support and simply use some copper wire to create the right contact pattern.Code and schematicsAll the code for the project and the schematics has been published as open source on my Github repository:https://github.com/dangiu/PicoMemcard3D-printed caseI've also designed a custom enclosure that can be easily 3D-printed and helps inserting the PCB in the correct position.https://www.thingiverse.com/thing:5488778Video?

From the late 1800s to the late 1900s, a typewriter was one of the best tools for writing documents. Sadly, they were largely rendered obsolete by the rise of home computers. I didn’t grow up using a typewriter, but a couple months ago I bought a Brother AX-25 electronic typewriter. It uses a daisy wheel (a spinning wheel with letters molded into it) and a motorized hammer to type text, rather than type bars (or strikers) like in a traditional typewriter. The sound it makes is unmatched even by the clickiest of keyboards. Each keypress results in a short buzz as the motor selects a character, followed by a satisfying clack. The AX-25 has a 16-character LCD, 128 kB of ROM for the typewriter’s firmware, 128 kB of storage, and 16 kB of RAM.These specs are pretty terrible by today’s standards. Luckily, it’s easy to repurpose old technology with open-source hardware! That’s why I used an Arduino and a Raspberry Pi to turn my typewriter into a Linux terminal.InspirationBack in high school, one of my friends was working on making a computer using a Z80 for a school project. He had it set up on a few breadboards in a briefcase, and after we talked about it for a bit, we decided that we would try to put it in an old typewriter. We wanted to make our own Commodore 64. We gutted an old electronic typewriter, but never got around to putting the computer in it. For the past 6 years, I've had that typewriter's shell sitting in my room.For a while, I wanted to turn the typewriter into a cyberdeck. I planned on putting a screen in it, and a Raspberry Pi with a hefty battery. I had that idea rolling around in my head until a couple years ago, when I saw CuriousMarc's video about his teletype turned into a Linux terminal. I wanted to do the same to a typewriter, but I never had the time to do it and couldn’t find a typewriter at any thrift stores. After graduating from college, I finally had enough spare time, and knowledge, to turn a typewriter into a computer.What it can doI can use all sorts of Linux commands, most CLI programs will work, but anything with a text-based interface (like Vim or Emacs) won’t work. By processing the escape sequences that the Raspberry Pi outputs, I can automatically toggle the typewriter’s formatting features. It can also print ASCII art! Here’s a video of it printing some art I found online, and some that I made using an ASCII art generator:Reverse-engineeringThe typewriter’s keyboard is wired up in an 8x11 matrix, and it connects to the typewriter using two connectors, one for the rows, and one for the columns.The keyboard connectors with jumpers to my circuit plugged into them.When you press one of the keys, it connects one of the row pins to a column pin, which the typewriter then detects. To figure out which pair of pins each key corresponds to, I connected each pair by hand one at a time, and wrote down what key was printed. I did this until I had the entire matrix mapped out.The typewriter matrix's layout.The typewriter uses a 7805 linear regulator to power its 5V components, and I was able to locate an unused 5V pad and ground pad that I can tap into to power my circuit. I had to add a heatsink to the regulator to accommodate for the increased power consumption of my circuit.Controlling the typewriterThe Arduino code is available on my GitHub repository if you’d like to look at it in more detail! My Arduino controls the typewriter using two multiplexers, one connected to each of the keyboard connectors. The multiplexer’s signal pins are connected so they can be used to connect pairs of pins on the keyboard connectors together. To send a key, the Arduino selects a pin on each multiplexer to connect them, which tricks the typewriter into thinking that a key has been pressed.My prototype for the typewriter control circuit.The Arduino is connected via serial to the Pi, which has the serial console enabled on its UART pins. I chose to use an Arduino in addition to the Raspberry Pi because I’m more familiar with them, and it makes interfacing with the Raspberry Pi’s UART console much easier. The Arduino and the Raspberry Pi communicate at a rate of 120 characters per second, but the typewriter can only type 12 per second. To prevent long messages from getting cut off, I added serial flow control to my code. This allows the Arduino to tell the Pi when to start and stop sending text. The Raspberry Pi is running Raspberry Pi OS Lite, since I only need access to the terminal.KeyboardTo scan the keyboard, I used essentially the same circuit; two multiplexers, one for the rows, one for the columns. The Arduino scans the keyboard one key at a time by selecting a channel on each multiplexer. When it detects that a key has been pressed, it sends that character to the Raspberry Pi so it can be processed.My prototype for the keyboard scanning circuit.I could have used the typewriter’s original keyboard for this project, but I chose to replace it with a custom mechanical keyboard with Matias Alps switches, which are super clicky and should feel great to type on!The custom keyboard layout I designed for my typewriter.ConclusionBy turning my typewriter into a computer, I was able to recreate the experience of using a teletype. Now I know what it was like to use Unix in the 1960s when it was originally being developed! The custom mechanical keyboard feels amazing to type on, and is a huge upgrade over the mushy membrane keyboard it originally had. With these upgrades, my typewriter is much more powerful now!

IntroductionFor a long time we developed several prototypes and teaching kits of mobile robots and we always used different modules to build them.Among these modules, we highlight: module to drive motors, module TP4056 to charge the project's batteries, an Arduino board and a shield for connecting the wires to the Arduino's digital inputs.This amount of modules often generates problems with bad connections and also makes connections more complex, with more wires. Also, they are not feasible to build a prototype or commercial product.After all, what to do to reduce the number of modules in the construction of mobile robot teaching kits?Based on this problem, we developed a circuit board with several features that will allow you to control your mobile robot. See the picture below.The files for this board are available for download from the PCBWay website. Take advantage now, visit the link, register and get a $5 coupon for you to win 10 free units of this electronic board.What features have been implemented in this electronic board?Below we have all the functionalities implemented in the electronic board.Charging system for Li-Ion battery with IC TP4056,DC-DC Boost Converter Circuit with 6V output,L293D Driver Circuit for the Motors, andArduino Standalone Circuit with the ATMEGA328P.Below we will present in detail all these functionalities implemented from the electronic schematic of the project.Control Board Electronic SchematicThe electronic circuit was divided into 4 parts: battery charging circuit, motor drive drivers, ATMEGA328P control circuit, circuit connectors and fixing holes. Below we have the electronic schematic of the project.Next, we will discuss each part of the circuit and how it works in the mobile robot control process.Mobile Robot Battery Charging CircuitMany users who program mobile robots constantly need to remove the batteries from the project to charge it. This process requires opening the robot and an external charger for charging.In addition, 2 18650 batteries are usually used to supply a voltage of 7.4V for project power. This requires more internal space and financial cost of 2 batteries.How to solve this problem?The first step for this was to create a circuit for charging Li-Ion battery with IC TP4056. The circuit structure is shown in the figure below.Before implementing the charging circuit, we want to use only 1 3.7V Li-Ion 16340 battery to power the project.In addition to avoiding the use of 2 18650 batteries, it will allow us to reduce the space consumed in the electronic board structure and in the prototype.However, how do we supply the ATMEGA328P chip with +5V and the motors with +6V?This question will be answered below.First, we implement the charging circuit with IC TP4056. It will be used to control and transfer energy to the 16340 Li-Ion battery.In addition to it, we use the DW01-A CI to ensure safety against overloads and short circuits during the battery charging process. In the electronic diagram of the figure above we have the battery represented by the BT1 element.After the battery we insert a JST connector to insert an ON/OFF button. This allows you to turn the project control circuit on and off. Now, let's go back and answer the previous question: how to power the ATMEGA328P chip with +5V and the motors with +6V?This lifting process is done through the circuit below. What circuit is this and how does it work?The circuit above is a boost type DC-DC converter. It has the purpose of raising the input DC voltage to another DC voltage level at the output.For this project we are raising the battery voltage from +3.7V to +6V.All of the above elements were calculated to provide this voltage. The MT3608 CHIP is the circuit's STEP-UP converter. Access the datasheet through this link.At the output of the +6V power circuit, we insert an SS315 diode to provide a voltage drop of 0.95V. This allows us to obtain a voltage of approximately +5V to power the control circuit of the ATMEGA328P.Control Circuit with ATMEGA328P MicrocontrollerThe ATMEGA328P Microcontroller circuit is shown below.Several microcontroller digital pins were used to control the pins of the 2 L293D drivers.L293D Driver for the MotorNext, we have the electronic schematic shown in the figure below. Each driver was used to control 2 motors. This therefore allows the electronic board to be used to control 2- to 4-wheel mobile robots.Finally, we created a way to monitor the project's power battery.Mechanism for Monitoring Battery VoltageOn several devices, such as notebooks and cell phones, for example, it is possible to observe the battery capacity level. This allows us to know when is the ideal time to carry out a new load.With that in mind, we created a means to implement this. To do this, we connect the battery output to the A0 terminal of the ATMEGA328P Microcontroller.From the input voltage it is possible to create a function and inform the battery capacity between 0% and 100%. We have determined a minimum voltage of 3..2V and a maximum voltage of 4.2V for 100%. Whenever the battery is close to this value, it is possible to generate an alert to the user to charge the project's battery.Finally, we provide some power and connection pins to the ATMEGA328P Microcontroller pins.Pins for Power and Connection of other DevicesHow to connect an ultrasonic sensor to this electronic board or an extra button, for example?This can be done through the male headers connector pins shown below.In total there are 4 connectors. Among them we have:1 connector with voltage potential 0V,1 connector with voltage potential of +5V, and1 connector with access to pins A1, A2, A3, A4, and A5.From these 3 connectors we can connect several sensors and other devices that will facilitate the navigation of the mobile robot.In addition to these pins, we have a connector to transfer the code to the ATMEGA328P Microcontroller with access to the +5V, GND, TX, RX, and RESET pins.See electronic schematic below.Below we present the complete structure of the electronic board of the project.Electronic Board Structure for Mobile Robot ControlAll images are inserted in this project.All files for this project are available in this PCBWay Shared Projects Comunitye. You will have access to the following files:Electronic schematic,Gerber file,List of materials,3D file of the electronic board for prototyping, andPick and Place file for SMD assembly.Future UpdatesAll files are available for download and you can get 10 free PCBWay units. To earn the $5 coupon and receive the 10 units you must access this link, create your account and order your plates for free.In future updates we will develop a new version with a USB flashing circuit to facilitate the direct transfer of code from the computer to the development board.All future PCB updates are available soon at the end of this article.Take advantage now and get 10 free units of this Arduino at your home. Click here and enjoy.

(DIY) AMIGA 500 - SWITCHLESS BOOT DRIVE SELECTOR Rev.3(RETRO VERSION of 3 RESET BOOT DRIVE SELECTOR)Hello,This circuit board has been tested on the Amiga 500 and works perfectly."A500 - Switchless Booter" is a circuit that allows you to change the boot priority of the Amiga 500's floppy drives by 3 consecutive Resets. (3 times pressing CTRL + left AMIGA + right AMIGA keys changes DF:1 to DF:0)If you use a second floppy drive connected to your A500, like GOTEK Drive or a mechanical floppy drive, (as DF:1), then you need a boot selector to boot from the second drive. (Most boot selectors work with a toggle switch, but not this one)While using "3 RESET BOOT DRIVE SELECTOR", if you want to toggle your floppy drives (DF:0 <> DF:1) you just need to press Reset keys 3 times. (Reset Keys are: CTRL and the two Amiga keys together)Benefits of Switchless Boot Drive selector:1) This "A500 - Switchless Booter" protects your Amiga 500. If you change the mechanical switch position while transfering data from floppy drive, this may cause damage to 8520 (Even CIA) or 5719 (GARY). Switchless booter do not let this happen.2) Most users need to make a hole on their Amiga 500 for attaching boot selectors mechanical switch. This "A500 - Switchless Booter" toggles drives electronically, there is no mechanical switch, so you do not need to make a hole on your your Amiga.Special thanks to Onur Sapci for his contributions to this project.COMPONENTS:2 Pcs. 74LS74 DIP14 ( Do Not Use HC or HCT ! )74LS12 DIP1474LS126 DIP14 ( Do Not Use HC or HCT ! )2 Pcs. BC 237 TO-92 TRANSISTOR2PCS. 20 PIN ROUND MALE HEADER (Get a 40 pin and cut it)DIP 40 IC SOCKET4 Pcs. DIP 14 IC SOCKET2 Pcs. 1N4148 DIODE100nF CAPACITOR (More than 10 Volts is OK.)10 MICROFARAD 25VOLT Electrolytic Capacitor (More than 10 Volts is OK.)47 MICROFARAD 16VOLT Electrolytic Capacitor (More than 10 Volts is OK.)4 Pcs. 4.7 K 1/4 WATT RESISTOR10 K 1/4 WATT RESISTOR47 K 1/4 WATT RESISTOR68 K 1/4 WATT RESISTORThe other version (programmable version) of this project is here:https://www.pcbway.com/project/shareproject/AMIGA_500___SWITCHLESS_BOOT_SELECTOR__3_RESET_BOOT_DRIVE_SELECTOR_.htmlIf you have a programmer capable of testing IC chips, such as the 74LS series, you should remember to test them before soldering. Some chips may be defective. (TL866 Minipro Programmer can test some logic ICs)In order to protect your electronical devices, always turn off your Amiga before connecting or disconnecting the cables or any other device.Gerber files can be changed at any time. Before paying for the PCBs, be sure to update your orders!Use this PCB at your own risk !Have funThank you.

The Neotron Pico is designed to run the Neotron OS - a CP/M or MS-DOS alike OS written in Rust. But, being open-hardware, you can program your Neotron Pico to do pretty much anything.The Raspberry Pi Pico is the core of the Neotron Pico. It uses PIO statemachines to generate 12-bit Super VGA video, and digital 16 bit 48 kHz stereo audio. It also has both I2C and SPI buses. SPI chipselects and IRQs are handled by an SPI-to-GPIO expander. This provides eight chip-selects and eight IRQs, to support up to eight expansion slots or peripherals. The eight chip-selects can be globally disabled, allowing the Pico to talk to either the I/O exander, or the selected expansion slot. The board has an SD Card fitted in the 'Slot 1' position, and the Board Management Controller in the 'Slot 0' position, leaving 'Slot 2' through to 'Slot 7' available for expansion. Each expansion slot has both I2C and SPI, along with unique chip-select and IRQ signals.This project exists because modern computers are too complicated for beginners to understand, but educational kits are often based around very old processors like the Z80 which can’t be programmed in modem programming languages like Rust.SpecsDual Cortex-M0+One dedicated for video/audioOne available for OS/Application use264 KiB SRAM2 MiB Boot ROMMicro-ATX form-factorSD Card slot for storage12V DC inputSPI and I2C based expansion busFour externally accessible expansion slotsDebug headers with signals for two more slotsDual PS/2 ports for Keyboard + Mouse16-bit 48 kHz stereo audio headphone out, line out, line in, and microphone in12-bit (4096 colour) VGA video outputCapable of 40x25, 80x25 and 80x50 text modesCapable of 640x480 @ 60 Hz 16-colour, 320x240 @ 60 Hz / 300x200 @ 70 Hz 256-colour graphics modesDesigned to run the Neotron OSOpen Source HardwareDesigned for hand assemblyComponents in detailProcessorThe main processor module is the Raspberry Pi Pico, which features:A Raspberry Pi Silicon RP2040 SoCDual-core Cortex-M0+ @ 133 MHz264 KiB internal SRAMNo internal FlashUSB 1.1SPI, UART, I2C and Programmable I/O peripherals26 GPIO pins2 MiB QSPI FlashOn-board LEDOn-board 5V to 3.3V regulatorUSB 2.0 Full-speed OTG micro-AB port4.00 USD / 3.60 GBP retail priceThe limited I/O on the Pico (we are using half the available pins just for the video output) is supplemented using a Microchip MCP23S17 SPI to GPIO expander, and an 3:9 decoder. See the I/O Expanders section for more details.