So when I was into using just a atmega328 dip chip I make a programmer header for it that also had a crystal and the capacitors need to make it function. I wanted to do the same for the attiny85. As you know you have to use a ISP programmer to flash the attiny85, This requires you to look up the pinouts and get a bunch of jumps out to wire it up. I wanted to eliminate all of this.
The original reason for this project is that I wanted to build a standalone RC2014 with keyboard and display. There is an official RC2014 serial keyboard, but I find it a little inconvenient for my big fingers and poor eyesight. I have plenty of old PS/2 keyboards laying around, so I figured I’d rig up a microcontroller to convert the PS/2 keyboard interface into a TTL-level serial interface that could be plugged directly into the RC2014’s serial port.
Along the way, I discovered that the very same circuit would make an interesting project to turn a PS/2 keyboard into a simple MIDI controller. So I adapted the circuit for that purpose as well.
Here I demonstrate how to use a single microcontroller pin to generate action-potential-like waveforms. The output is similar my fully analog action potential generator circuit, but the waveform here is created in an entirely different way. A microcontroller is at the core of this project and determines when to fire action potentials. Taking advantage of the pseudo-random number generator (rand() in AVR-GCC’s stdlib.h), I am able to easily produce unevenly-spaced action potentials which more accurately reflect those observed in nature. This circuit has a potentiometer to adjust the action potential frequency (probability) and another to adjust the amount of overshoot (afterhyperpolarization, AHP). I created this project because I wanted to practice designing various types of action potential measurement circuits, so creating an action potential generating circuit was an obvious perquisite.
I was presented with a need to rapidly develop a pulse generator to take a TTL input and output a programmable output (for now 0.1 ms pulses at 20 Hz for as long as the input is high). I achieved this with a one-afternoon turnaround and the result looks great! This post documents the design and fabrication of this prototype device, with emphasis placed on design considerations and construction technique.
Designed and built by Simon Inns, a universal USB to quadrature mouse adapter project – SmallyMouse2:
SmallyMouse2 is a universal USB to quadrature mouse adapter for many 8-bit and 16-bit retro computers and allows the use of modern USB mice on machines such as the Acorn BBC Micro, Acorn Master, Acorn Archimedes, Commodore Amiga, Atari ST and many more. Unlike most existing mouse adapters, SmallyMouse2 implements a fully USB compatible interface (most current adaptors are PS/2 based) this allows the use of any modern mouse including those that use wireless communications.
Steve Smith from ProjectAVR has published a new build:
On the board, I included several options to tailor the design to the builders taste. Provision for both a digispark board or bare ATTiny85 chip, small or large tact switches and a jumper to defeat the LEDs supply resistor for extra brightness.
I chose to build the Digispark version first. It went together easily (bar a hole size issue, more of that later) and I programmed the digispark via it’s own USB socket. And… the board completely failed to start up. It took me some time to realise that I’d got the USB power connections inverted! Lucky I’d added a reverse polarity diode! I de-soldered the USB ‘A’ type plug and re-soldered it on the back side of the board flipping the connections. I don’t have the correct type of USB plugs anyway, so it’s a bit of a kludge at the moment. However, once this was done, the board sprung to life. When powered up, the Digispark’s micronucleus bootloader kicks in for a few seconds and then the Clapper code starts.
Traffic lights are all around us, and they seem simple enough but are they really? Real traffic lights can be a very complicated system because it requires sophisticated control and coordination for smooth and safe traffic.
The traffic light I made is much simpler. My sister works in a kindergarten where kids needed a simple traffic light for when they are riding their bikes on the playground.
The traffic light uses some cheap LEDs from China, a step-up converter and an Atmel attiny841 microcontroller to change the light from red to green at a programmed interval.
The Apple II was one of the first home computers. Designed by Steve “Woz” Wozniak, it used the MOS technologies 6502 processor, an 8-bit processor running at about 1 MHz. [Maxstaunch] wrote his bachelor thesis about emulating the 6502 in software on an AVR1284 and came up with a handheld prototype Apple II with screen and keyboard.
Originally, [maxstrauch] wanted to build an NES, which uses the same 6502 processor, but he calculated the NES’s Picture Processing Unit would be too complicated for the AVR, so he started on emulating the Apple II instead. It’s not quite there – it can only reference 12K of memory instead of the 64K on the original, so hi-res graphic mode, and therefore, many games, won’t work, but lo-res mode works as well as BASIC (both Integer BASIC and Applesoft BASIC.)
[Maxstrauch] details the 6502 in his thesis and, in a separate document, he gives an overview of the project. A third document has the schematic he used to build his emulator. His thesis goes into great detail about the 6502 and how he maps it to the AVR microcontroller. The build itself is pretty impressive, too. Done on veroboard, the build has a display, keyboard and a small speaker as well as a micro SD card for reading and storing data. For more 6502 projects, check out the Dis-Integrated 6502 and also, this guide to building a homebrew 6502.