Serial USB For Any AVR Microcontroller

October 23, 2013 by Brian Benchoff 30 Comments

If you’re using an AVR microcontroller and you’d like to add USB to a project, there are a lot of options out there for you. Both LUFA and V-USB add some USB functionality to just about every AVR micro, but if you’d like a native serial port, your only options are to look towards the USB-compatible Atmel micros.

[Ray] looked at the options for adding a USB serial port and didn’t like what he saw; seemingly, this was an impossible task without a second, more capable microcontroller. Then he had an idea: if the goal is only to transfer data back and forth between a computer and a microcontroller, why not write an HID-class USB serial port?

[Ray] based his project on The V-USB library and created a new HID descriptor to transfer data between a micro and a computer. While it won’t work with a proper terminal such as Putty, [Ray] managed to whip up a serial monitor program in Processing that’s compatible with Windows, Linux and OS X.

In the video below, you can see [Ray] using an ATmega328p with a standard V-USB setup. He’s transferring analog values from a photoresistor as a proof of concept, but just about everything that would work with a normal serial port will work with [Ray]’s library.

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Turn A PC On With A Knock And An ATTiny

October 21, 2013 by Marsh 14 Comments

knockAttiny

Pressing the power button on your computer usually isn’t too much trouble, unless your computer is stored away somewhere hard to reach. [Joonas] has been hard at work on a solution that would also impress his friends, building a knock sensor to turn on his PC.

For around $10 in parts he put together an ATTiny45 that emulates a PS/2 device, which takes advantage of his computer’s ability to boot upon receiving PS/2 input. The build uses a Piezo buzzer and a 1M Ohm resistor as a knock sensor exactly as the official Arduino tutorial demonstrates, and one of those PS/2-to-USB adapters that are most likely lurking in the back corner of every drawer in your office.

[Joonas] used AVRweb to disable the 8X clock divider so there’d be enough clock cycles for PS/2 communication, then loaded some test code to make sure the vibrations were being detected correctly. You can check out his Github for the final code here, and stick around after the break for a quick video demo. Then check out a similar hack with [Mathieu’s] home automation knock sensor.

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The Most Minimal Homebrew Computer

October 21, 2013 by Brian Benchoff 31 Comments

Perfection is achieved not when there is nothing more to add, but when there is nothing left to fail. Going by that metric, [Stian]’s three-chip 6502 homebrew computer is the epitome of perfection. It’s a real, working, homebrew retrocomputer using only three chips: a CPU, some RAM, and a microcontroller to bootstrap the computer and provide a video output,

The key to this minimalist build is having the entire boot process controlled by an ATMega16 microcontroller, This interfaces to the 6502 through a dual-port SRAM, a 1 kilobyte Cypress CY7C130. This dual-port RAM allows the CPU and microcontroller to access the same bit of memory, making it easy to bootstrap a computer from a bit of AVR code.

Output is provided with [Stian]’s ATMega video text generator putting a 37×17 characters on any television with an RCA jack. While input isn’t handled yet, [Stian] says it should be possible with his AVR PS/2 keyboard library.

While other 6502 homebrew computers such as [Quinn Dunki] Veronica can reach unparalleled heights of complexity, there is a lot to be said about the minimalism of [Stian]’s three-chip computer. With some clever coding and a modified parts list, it may well be possible to put a retrocomputer in the hands of everyone with a bare minimum of cost and parts.

Build A Sensorless Brushless DC Motor Controller

October 19, 2013 by Todd Harrison 43 Comments

[Davide Gironi] shows us how to implement a sensorless brushless DC motor controller (sensorless BLDC) using an ATmega8 microcontroller. In order to control a BLDC motor you need to know its rotational sequence position and speed so you can calculate and apply the correct current phase sequence to the motor windings at just the right time.

Simply said, sensorless BLDC means you’re not using a purpose built sensor to determine the motor’s position and speed, however, you are sensing the motor’s sequence position using the back EMF signal coming from one of motor’s coils that is not currently receiving power. When this back EMF signal crosses zero voltage a microcontroller can calculate the rotational speed and when to switch to the next power sequence. This technique is not good for position control motors but is great for continuous motors like computer fans and drives were the slightly reduced wiring costs make this type of BLDC control favored.

If you want to build a BLDC controller we recommend starting with [Davide’s] last project on sensor controlled BLDC motors. You can also checkout these interactive demonstrations for more understanding on the different BLDC configurations.

Follow along after the break to watch the video demonstration of [Davide’s] sensorless BLDC controller controlling a motor from CD-ROM drive.

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Making A Diode Matrix ROM

October 18, 2013 by Mathieu Stephan 34 Comments

Here is a nice project that allows youngsters (but also adults!) to actually see the data stored in a Read Only Memory (ROM). The memory shown in the picture above is made of diodes. [Scott] made it as a part of his Barcamp Fall 2013 presentation about visualizing ROMs. He starts his write-up by stating the obvious: this memory is not practical. Nonetheless, it still was a fun exercise to do. [Scott] then greatly described all the different kinds of read only memories that you can find out there, with a few words explaining how they work. In his diode ROM, bits are ‘programmed’ by adding (or not) a diode between a given data line (anode) and an address line (cathode). When pulling low a given address line, the corresponding data line will only be pulled low if a diode is present. [Scott] finally checked his circuit by using a very old device programmer which could only be run in DOS.

Teach An Old LCD New Tricks

October 16, 2013 by Adam Fabio 43 Comments

pic-lcd

[Art] has done some amazing work with character LCDs. He started with a classic character LCD. These LCDs are typically controlled by Hitachi HD447XXX compatible controllers. Hitachi’s controllers allow several custom characters to be defined. We’ve used those characters in the past for applications like spinners and bar graphs. [Art] took things to a whole new level. He created a double buffered LCD graphics library which allows these old LCDs to perform tricks usually reserved for graphical LCDs. Even more impressive is the fact the whole thing runs on a Microchip PIC16F628A programmed mostly in PICBASIC.

According to [Art’s] thread on the PICBASIC forum, he is using the custom character memory as a framebuffer. The LCD is set to display all 8 custom characters. Each frame is then in the PIC’s RAM. The completed frames are then pushed to the custom character memory of the Hitachi LCD controller. The result is a very smooth update rate on the LCD. [Art] wrapped the whole example up in a video reminiscent of the C64 demoscene.

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Breadboarding With A ARM Microcontroller

October 15, 2013 by Brian Benchoff 89 Comments

NXP’s LPC1114 ARM microcontroller is in a class all of it’s own. ARM microcontrollers are a dime a dozen, but this fabulous chip is the only one that’s housed in a hacker and breadboard friendly PDIP package. However, breadboard setups usually won’t have the luxuries of a true development platform such as flashing the part, single stepping through the code, and examining memory. [Steve] found an interesting solution to this problem that involves a Dremel and hacking up even more hardware.

[Steve] found a few LPC1769 dev boards that include a debugger and a way to program these chips. Simply by hacking off the programmer and debugger portion of this dev board with a Dremel tool, [Steve] had an easy to use interface for his breadboardable ARM.

After connecting the power rails to his breadboarded chip, [Steve] connected his programmer up and set up a gcc toolchain. For about $25, he has a breadboard friendly ARM microcontroller with full debugging capabilities.

This isn’t the first time we’ve seen a few people play with this DIP28 ARM chip; someone even milled this 600 mil chip down to 300 mils for even easier prototyping. Still, this is the best and cheapest way we’ve seen yet to turn this ARM into a proper prototyping platform.