Paul's Arduino

This is pretty cool – I took the TVout library, the Wiichuck library and wrote a 3D library. Put them all together and got a nunchuck controlled 3D shape on TV. Movement in the nunchuck is detected by the arduino, then the cube is redrawn according to new angle of the controller.

At this point I ran out of memory but it wouldn’t be too hard to set up the shapes in FLASH instead of RAM. The hardware isn’t too complicated, just a few resistors and a pot for the speaker.

3d wireframe library header and source

Code to tie everything together

OK so this is tiny but it implements the Bresenham line drawing algorithm and draws a clock…

The code is pretty simple.

Its running about 100x faster in this video so I can show how it works.

[[Schematic soon]]

Next up – persistance of vision…

Pretty simple hardware – using the same 8 bit shift register from the thermometer project and driving LEDs from the outputs.

The clever bit will be the software – but more about that next time. For now, here is the circuit diagram.

So, for our first trick we thought we’d try and conjour up a thermometer, and then we added a clock as well – just for good measure.

Pretty much all the parts came from Cool Components or Maplin. I got a cheap 2 line display on sale which was the starting point, then wondered what we could create to educate…

The LCD interface is through 3 wires and a 4094 shift register. I’ve taken the example 3 wire LCD code from the arduino playground at http://www.arduino.cc/playground/Code/LCD3wires and modified and extended it a little to provide some positioning functions and improve the number drawing code.

Schematic and Breadboard

Explanation

The thermometer functionality comes from TMP102 module which is connected through an I2C bus, implemented with the Wired library. The I2C interface is very easy to use, call

Wired.begin

in setup() to initialise it, then its a simple case of reading the latest temperature values. The addressing here assumes that the ADD0 line on the module is pulled to ground:

// Temperature module commands and registers
int  TMP_RD = 0x91;
int  TMP_WR = 0x90; //Assume ADR0 is tied to VCC
int  TEMP_REG = 0x00;
int  TEMP_ADDR = 0b1001000;

int ReadTemperature()
{
 int  val_h = 0;
 int  val_l = 0;

 Wire.requestFrom(TEMP_ADDR, 2);
 val_h = Wire.receive();
 val_l = Wire.receive();

  //  calc temp in C
 int tempint = ((val_h << 8 ) | val_l) >> 4;      // combine and shift
 float tempflt = float( tempint ) * .0625; // calculate actual temperature per chip doc
 return int(tempflt);
}

The clock works by using the millis() function  to establish a base time and a corresponding millisecond count – then we can update the display anytime by calculating the time since a known base. If the millis() wraps we adjust the base to the last known good value and go from that. There will be a little bit of creep there but only once every 1193 hours ish…  Clock adjustment is through two switches which pull digital inputs to ground – if they are low we increment the base Hours or Minutes value depending which button is pressed. The internal pull up resistors are used to ensure the inputs don’t float about when the button isn’t pressed, here’s an extract:

// set up input
 pinMode(HOURS,INPUT);
 digitalWrite(HOURS, HIGH);       // turn on pullup resistor

//Adjust the clock
 boolean    bRet = false;         // was an adjustment made
 if (digitalRead(HOURS) == LOW)   // read the input switch
 {
   iBaseH++;
   if (iBaseH > 23)
   {
     iBaseH = 0;
   }
   bRet = true;
 }

After that all you need to do  is just get data for the temperature or the time and then call the display routines.

The code for the whole thing is here.