AT3421 AVR…

                                    AT3421

                  AVR Contest Entry AT3421 Description

LET'S GET READY TO RUMBLE

If you're actively involved in any of the martial arts such as boxing, kick-
boxing, karate, tae-kwon-do, etc. or are acquainted with them from television or
the movies, then that heavy bag that the athletes are hitting on is familiar to
you. It is omnipresent because it has withstood the test of time and has proven
itself as a great tool for such training. Helping to strengthen one's strikes
and increase their accuracy and stamina.

The only problem with it, once you begin using it regularly, is that you realize that
your workouts with it can be so one-sided and boring! It just sits there and takes your
punishment without any complaint or feedback. How much fun is that? Wouldn't it be
great if we could change that by adding some excitement and motivation to our workouts
with it? That's exactly what we're going to do in this project with the help of ATMEL's
megaAVR family of microcontrollers.


SOME HISTORY

This idea has been in the making since 1993. Back then it was originally PC-
based, making it bulky and inefficient. During the last ten years or so it has
been poked, prodded, expanded upon and then `minimized' as it evolved towards a
microcontroller based product. What better way to easily and efficiently bring
it into the 21st century than with this fun project.


DESIGN OVERVIEW

This project is a real-time interactive martial arts training system.
Incorporating high-quality digitized audio and speech feedback, it simulates a
bout with an opponent while providing audio motivational cues and other helpful
feedback. It offers three different skill level settings, with bouts ranging
from three to six rounds, and is designed to be very user-friendly and
economical. The sensor(s) and speaker are separate from the electronics
themselves and connected with regular 2-conductor wire via jacks.

The digitized audio is via Winbond's ISD2500 series of CHIPCORDER ICs. The 2560
has been chosen, giving us the highest quality sample rate and a full minute's
worth of audio messages.

The impact sensor we will use in this project is a condenser microphone. Any
other type of sensor that's out there (piezoelectric, accelerometer, etc.) can
also be easily used; but for pure economy, efficiency, simplicity, hardiness,
and yes, even novelty, a common microphone is hard to beat.

Thanks to the megaAVR's multitude of I/O pins we can also implement quite a few
mechanical, normally-open tactile switches to act as more `specific' strike
areas on the target. We can also use more than one microphone sensor since we're
limited only by the number of ADC channels. Here we'll concentrate on the
simpler single microphone version.

As mentioned earlier, the microcontroller of choice comes from ATMEL's megaAVR
MCU family; the 40 pin ATmega16 was chosen for the experimentation phase of the
project ­ lest there be any limitations! It includes, among a plethora of


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bidirectional I/Os, an 8-channel, 10-bit ADC, 16 kilobytes of FLASH memory and
512 bytes of EEPROM. After research and testing is complete it is very simple to
move to the smaller, more cost and power-efficient MCUs such as the ATmega8L and
the newest ATmega88(V).

Looking at the design's block diagram, we see the four parts that make up this
design. The microcontroller's job is to `listen' for any impacts on the sensor
through its built-in ADC and, while monitoring the time remaining, register the
impact force and track the user's performance during the workout; it also uses
its built-in EEPROM to store the performance data. At the appropriate time, it
will `wake up' the ISD chip and tell it which corresponding audio message to
play through the speaker. The third part is the DS275 RS-232 transceiver chip
which provides the interface between the ATmega16's USART and the PC's serial
port. Finally, the power conditioning circuitry is made up of a 78L05 voltage
regulator and a few capacitors for filtering and de-coupling.


POWER TO THE PEOPLE

The 78L05 is a three pin voltage regulator that takes 9VDC and supplies 5VDC at a
maximum of 100mA. It offers current and temperature overload protection.

There is a 10uF electrolytic capacitor across the regulator's outputs for
filtering any noise and helping to provide a clean supply to their respective
circuits.

The current consumption of the circuit is fairly low. According to their
respective databooks, the ISD2560 draws a maximum of 30mA when operating (10uA
power-down mode) and the ATmega16 draws a maximum of 15mA when running at 8MHz
(