On Sunday, my partner Eric and I had a table at the first-ever Kitsap County, Washington Mini Maker Faire, (Maker Faires are sponsored in part by Make Magazine).  It was a gloriously nice day for the Seattle area and one of the few nice ones we'd have this year.  Over 400 people attended which was a nice scale and allowed lots of time for interaction.

We decided that we wanted to present sort of a broad view of "making" - that the technology to go from design to hardware to real-world applications was within everyone's reach.  Eric planned to combine "techie" and "foodie" and demonstrate sous-vide cooking as something that "maker" technology makes possible.

A number of devices have been decribed on the pages of Digital-DIY that use the I2C interface, including real time clocks, temperature sensors, WII Nunchuks, port expanders and even thermocouple interfaces and a number of Swordfish modules are available to make using these devices simple.  The TAP-20-USB board is based around using I2C for expansion.

Hack-A-Day posted about this tutorial available on Embedded Labs.  It's a nice overview on how to use I2C devices.  Have a look.

Lab 14: Inter-Integrated Circuit (I2C) communication

I2C (Inter-Integrated Circuit) is a short distance serial interface that requires only 2 bus lines for data transfer. It was invented by Philips in 1980′s, originally to provide easy on-board communications between a CPU and various peripheral chips in a TV set. Today, it is widely used in varieties of embedded systems to connect low speed peripherals (external EEPROMs, digital sensors, LCD drivers, etc) to the main controller. In this experiment, we will cover an overview of I2C protocol, its implementation in PIC microcontrollers, and the method of connecting single and multiple devices on a common I2C bus. We will demonstrate the technique by connecting two I2C EEPROM chips (24LC512) and an I2C compatible temperature sensor (DS1631) with PIC18F2550 microcontroller.

Read the Complete Article

Microchip released a USB Bootloader which supports pretty much every device with USB (back in 2008 - I must be living under a rock). It can be downloaded on the Application Libraries page, read on before you do. The package includes the source code and a compiled program for the graphic user interface, screen shot below.

* note - this is the full version of the GUI - I've included it in the download package *

The Microchip bootloader includes support for a development board (reset switch/LEDs) which typically isn’t needed for practical use. Joe Hanley (more commonly known as Captainslarty on the proton site) went one step further and removed the additional hardware support, and then packaged all of the precompiled firmware for popular PIC18 devices. At the time of writing, the USB bootloader firmware supports the 18F14K50, 18F2450, 18F2455, 18F2458, 18F2550, 18F2553, 18F4450, 18F4455, 18F4458, 18F4550 and 18F4553 (with 8 or 20Mhz crystal oscillators).

Thanks to Joe, the process of working with the USB Bootloader is simple:

1. Download the PIC18 USB Bootloader pack (and unzip it).
2. Flash the appropriate firmware to your device (using a PICKit 2, for example).
3. The device can now be flashed with a USB cable and PC software.

Note you do not have to use MPLAB or have any knowledge of C18. Once the device is loaded you can flash the device with firmware written in any language. If you want to venture out of the precompiled configurations, then you'll need to get familiar with C18 and have a close look at the original Microchip code.

DIY Printed Circuit Boards

for the home hobbyist

methods and mistakes

By Doug Bezaire

“MrDeb”

Making a printed circuit board for that one of a kind project can be a challenging experience at best.

I have tried most of the standard methods of actually applying the circuit design to a copper clad board then etching using several different chemicals.

But before one can apply a design to a copper clad board, a design must be produced. There are many design programs available, some free and some require to be purchased.

I personality have only tried three different FREE cad design downloads.

The first being Express PCB. An easy program to learn and the results are good. But if you have a design that you want multiple boards then you need to have Express PCB make your boards. Can get expensive. If you have never done any board designs then I suggest getting your feet wet with simple designs.

In the first article on LED Calculations, we looked at ways of determining the required series resistor.  Since an LED's forward voltage is not a linear function of current through the LED, there was some controversy about the simple "close enough" method of determining an undocumented LED's characteristics.  This article takes a look at a real-world example in the lab.

We want to calculate the series resistor for an LED of unknown characteristics.  Consider this to be a small LED of the type you might drive directly with a microcontroller, not one of the new monster LEDs for lighting up the night.  Some of those are amazing but well outside of this scope of discussion.  Furthermore, we'll evaluate the results based on using the nearest 5% resistor value from the standard resistor series.

The test victim subject will by a T1¾ (5 mm) RGB (red/green/blue) LED from ebay.  To be honest, these LEDs are craptastic.  The red section is much less intense than the green or blue sections.

RGB LEDs have three independent LED dyes in the same package; for this testing only one element was operated at a time.