Here’s the timer interrupt that services the analog to digital converter and the multiplexing of the LEDs:

ISR(TIMER2_OVF_vect){
static unsigned char activeLine=0;
static unsigned char adcChannel=0;
PORTC=0xFF;
PORTA=0xFF;
selectLine(activeLine);
PORTC=~green_display[activeLine];
PORTA=~red_display[activeLine];
activeLine++;
if(activeLine>7){
activeLine=0;
}
switch(adcChannel){
case 0: x_accel=(ADCH-x_flat)/10;
if((x_loc<500)&&(x_accel<0)){ x_accel=0; } if((x_loc>7500)&&(x_accel>0)){
x_accel=0;
}
x_vel=limit(x_vel+x_accel,-MAXVELOCITY,MAXVELOCITY);
ADMUX=0xE1;
adcChannel=1;
break;
case 1: y_accel=(y_flat-ADCH)/10;
if((y_loc<500)&&(y_accel<0)){ y_accel=0; } if((y_loc>7500)&&(y_accel>0)){
y_accel=0;
}
//if((abs(y_accel)>1)||(abs(y_vel)>20)){
y_vel=limit(y_vel+y_accel,-MAXVELOCITY,MAXVELOCITY);
//}else{
// y_vel=0;
//}
ADMUX=0xE2;
adcChannel=2;
break;
case 2: z_accel=(ADCH-125);
ADMUX=0xE0;
adcChannel=0;
break;
default: adcChannel=0;
}

}

And the main loop:

while(1){

if((abs(x_vel)>STICTION)||(abs(y_vel)>STICTION)){
x_vel=(int)((ELASTICNUMERATOR*(long int)x_vel)/ELASTICDENOMINATOR);
x_loc+=x_vel;
y_vel=(int)((ELASTICNUMERATOR*(long int)y_vel)/ELASTICDENOMINATOR);
y_loc+=y_vel;
}
if(x_loc<0){ x_loc=-x_loc; x_vel=-x_vel; } if(x_loc>7999){
x_loc=7999;
x_vel=-x_vel;
}
if(y_loc<0){ y_loc=-y_loc; y_vel=-y_vel; } if(y_loc>7999){
y_loc=7999;
y_vel=-y_vel;
}
x_pos=(unsigned char)(x_loc/1000);
y_pos=(unsigned char)(y_loc/1000);
plotBall(x_pos,y_pos);
_delay_ms(50);

}

I just added the 3-axis accelerometer, but haven’t soldered on the supporting components. Also I still need to add the Li-Po charge IC. I am currently using the STK500 both to power and program the board.

So without further ado, here are some pics…

Mazetrix project

Mazetrix Bottom

Mazetrix Top

My board is for a project based on the Tiletoy, and incidentally not unlike the Space Invaders Button, the Awesome and 64Pixels.

Many moons ago I managed to score several 8×64 Red-Green matrix displays salvaged, evidently, from a casino display. Even though I had managed to reverse engineer them and figure out how to display nifty messages, they were just too large and too COTS for me. I removed the 8×8 LED matrices (matrixes?) and designed a small board to run them. The display is run directly from an ATMega128, using a half-H bridge on each column so I can use the entire matrix as a sensor. Additionally, I have added a MMA7260 triple axis accelerometer. Last but not least is an IR LED pointed in each of the cardinal directions, also connected to be used as an input and an output, for communicating to neighbor modules(PDF link).

The ultimate goal is to create tiles with a red maze and a green “ball” than you can manipulate by tilting, just like the good old labyrinth game. When you get to the edge of a tile, you can connect another, which will attach magnetically, and the maze will continue on the new tile.

I’ll add more updates when I start building.

Here’s a few images to satisfy the curious:

schematic

Mazetrix Layout

Deskpet is a project that I am working on to create a small robot to live on my desk as a pet. One of the things I have learned at work is that it is much harder to build something if you don’t know exactly what it is supposed to do. So here goes; high level design goals for Deskpet:

1. The major goal for the Deskpet is to construct a pet. It needs to live on my desk and generate an emotional attachment.
   • Sufficient output to be “interesting” – If all it has is a pair of motors, I can make it dance, but it would be much easier to generate an emotional attachment if it has other methods of expressing itself.
   • Sufficient input to be interactive – I want to be able to play with my pet, so it needs to be able to sense it’s surroundings, toys and possibly me.
2. Automatic recharge – If it is going to seem alive, I can’t keep having to put it on the charger.
3. Wireless communication and bootloading – This is going to require A LOT of firmware work on my part, so it ould be easiest if I could download new firmware without even toucing the ‘bot.
4. I will not be concerning myself with availablilty or cost of components with respect to eventually making kits available. This will be a project for me.

Well, that should be enough to keep me busy……..

Family and friends have been having a lot of fun driving it around.

My end goal is to let the ‘bot talk to a base station connected to a PC. I REALLY want to write an RF bootloader, so I can reprogram without touching the ‘bot. This is the hardware for the base station ( Still need to write the software and firmware):

Here’s a pic of the prototype:

P.S. If you are looking for a cool off-the shelf ‘bot, the 3pi from Pololu looks really nifty. Can’t wait until it comes out…

I finally got around to taking some pictures of the base:

2) The IS471F requires 4.5V but I want to run from a max of 3.3V. Looks like I’m going to need to find another solution for proximity detection.

3) Charge pump for the color sensor LED’s: MAX1595? I have used some of the Maxim capacitor charge pumps in the past and they work well.

Input

• Color/Line sensor
• Linear Hall effect sensor
• 2 way IR proximity sensor
• Ambient light level sensor
• Wireless data
• Battery level sensing
• Battery charge input
• Pushbutton

Output

• 2X Motors
• Speaker
• Wireless Data
• OLED “face”

And here’s what I have so far for each:

Color/Line Sensor:

NECM005 RGB LED and TEMT6000 light sensor

Linear Hall Sensor:

Not sure yet. I like the 3 pin SIP devices from Allegro, but they need 4.5V. I would like to keep everything possible running from a 3V or maybe 3.3V supply.

IR Proximity Detect

2X IR LED’s and IS471F modulated detector. Could also be used for IR homing beacon for charging station. To avoid interference with the proximity detect, sending a specific pulse from the LEDs would trigger the charging station to transmit a response.

Light Level

CDS Cell or TEMT6000 light level sensor

Wireless Data:

Nordic nRF24L01 board from Sparkfun

Battery Level:

Voltage divider to ADC on the main processor

Battery Charging Circuit:

MAX1555 Lithium charge controller

Pushbutton:

SMT Momentary Normally Open SPST

2X Motors:

LB1836M Low Voltage Dual H-Bridge and 2X GM10 geared pager motors

Speaker:

Citizen Micro Speaker from Electronics Goldmine.

OLED “face”:

uOLED96 from 4DSystems. I have an older version than the one shown in the link with 8MB internal flash, and no uSD slot.

Still left to work on:

• Battery – Size and mounting locations
• Charging method – How does the robot find & connect to the charger?
• Decide on a Hall Sensor
• Find an LED charge pump since the G and B LEDs require 3.6 V

I have three “airwires” left. The auto router choked on this board, so this was the best I could do manually. I added some vias so I could solder a jumper in to connect the nets.