She has a heart

This is not quite everything I wanted to get accomplished this weekend, but I did make some solid progress. All the electric components are soldered and working! In the process, I realized that I know nothing about soldering. Best lesson? Keep your soldering iron tip clean!

It took me quite a while to get everything drawn out and even longer to get it all soldered and working, but it was a great learning experience and super fun.

This is the entire unit... arduino, i2c multiplexing shield, equalizer shield, bluetooth breakout board, 4 ADXL 345 accelerometers, and an electret microphone. Only things missing from the shot are the 450 LED pixel points, the 6v 12Ah sealed lead-acid battery, and another battery to run this unit (I'm going to run the lights and controller off of separate batteries).

LightWalker's guts.



This is the i2c multiplexing shield with TCA9548A i2C switch. It allows me to hook up the 4 accelerometers that all have the same i2c hardware address to a single i2c line. The board can handle up to 8 units with the same address, so maybe I should do a spider for next year?

The big trick here was that I hooked up my SCL and SDA lines to where they were printed on the board but failed to realize that the board didn't connect those to the arduino's analog 4 and 5 pins like my board needed. I think newer boards would work through the stackable headers and the SCL and SDA holes printed on the board. Once I realized I was working with an older setup and re-routed them, all was good.





bottom of the i2c multiplexing shield

top of the i2c multiplexing shield







Here's the equalizer shield. I'm only using one of the  MSGEQ7 chips on here for a single audio channel, so it's kind of overkill, but it does give me a nice stackable shield and pins to hook the microphone and bluetooth to.



equalizer shield w/
electret microphone

And, just for completeness, the arduino compatible shield from seeedstudio...

the seeedstudio arduino
compatible board I'm using

multiplexing working!

The TCA9548A soldered onto a
Schmartboard w/ male pins

Surfing, scuba diving, swimming with turtles, and downing boat drinks in Hawaii must go a long way towards making one smart and productive cause I've only been back from Hawaii for 24 hours and I've already finished a book (Something Wicked This Way Comes), got 8 hours of sleep, worked for 8 hours, ate two tacos, and gotten my multiplexing chip working!

I posted a while back about getting the TCA9548A I2C multiplexing chip and the Schmartboard and just now finally got it all soldered up and tested it out. The soldering was ridiculously easy for a chip this size. Got to hand it to Schmartboard for finding a slick, easy to use design. Literally took me 10 minutes from start to finish including heating up the iron and soldering a test chip. In retrospect, I should have soldered female connections onto this board or even gotten the Schmartboard arduino shield, but I'm definitely a noob and this is what happens. It'll work for now.

The longest part of the whole ordeal was figuring out how to wire the thing up, but in the end, I got it all working and was even able to hookup two ADXL-345 accelerometers to it and get readings from both. Again, the main point of this chip is that I want to hook 4 accelerometers up to my board over I2C but all the accelerometers have the same I2C address hardcoded. So, with the TCA9548A, I can control which one I'm talking to at any point in time.

Here's the sample Arduino sketch I threw together to demo things:

#include <Wire.h>
#include <ADXL345.h>
#include <SPI.h>
#include <TCL.h>

#define TCA9548AADDR 0x74 //1110100

// For now, one object works...
ADXL345 adxl;
unsigned long lastStatus = millis();
double xyz[3];
 
void setup()
{
    Serial.begin(9600);

    Wire.begin();

    Serial.print("initing adxl0...");
    selectI2CChannels(0x1);
    adxl.powerOn();
    Serial.println("done");

    Serial.print("initing adxl1...");
    selectI2CChannels(0x2);
    adxl.powerOn();
    Serial.println("done");
}
 
void loop()
{
    unsigned long currentTime = millis();
    bool printStatus = false;

    if (currentTime > (lastStatus + 500))
    {
        printStatus = true;
        lastStatus = currentTime;
    }

    selectI2CChannels(0x1);
    adxl.getAccelemeter(xyz);
    if (printStatus)
        printXYZ("ONE");
 
    selectI2CChannels(0x2);
    adxl.getAccelemeter(xyz);
    if (printStatus)
        printXYZ("TWO");
}
 
void selectI2CChannels(int channels) 
{
    Wire.beginTransmission(TCA9548AADDR);
    Wire.write(channels);
    Wire.endTransmission();  
}

void printXYZ(char label[])
{
    Serial.print(label); Serial.print(": ");
    Serial.print(xyz[0]); Serial.print(",");
    Serial.print(xyz[1]); Serial.print(",");
    Serial.println(xyz[2]);
}

Credit for being able to figure out the code and switch between the two accelerometers should go to Kerry Wong as the basis for my test is from his blog.

I'm pretty excited about things at this point, they are really starting to come together. I think I'm past due for a cool video update showing a lot of what I've done come together. Back with that as soon as I can...