Arduino & LIS302DL

Ages ago I bought an LIS302DL from Sparkfun. One of the old (little bit) messed up ones, but still 3 axis accelerometer with I2C output. No external parts. No pain. Fine!

Before I go in any further investigation. I need to get it up & running with my arduino (actually an boarduino – but who cares?). Read all the nifty details after the break.

The hookup is very easy (but a little bit off standard) – remember we use I2C:

• VCC is connected to pin 13 – so you can power this from the arduino. But you should also be able to power it directly from VCC. Remember it was 3.3V
• GND is connected to GND – this was a bit obvious.
• SCL is connected to analog pin 5 (arduino’s I2C SCL)
• SCA is connect to analog pin 4 (arduino’s I2C SCA)
• MISO was tied to GND – in order to select the I2C address 28 – tie this to VCC and you got address 29 – if you want to use two LIS302DL – there is perhaps some reason for this – who knows?
• INT2 is connected to pin 2 – in order to be able to use the interrupt. I did not – who knows? Perhaps I will do it later

The basic setup was the same as with my ADJD experiments. A 3.3V breadboard and the same I2C-routines for reading and setting registers:

void writeRegister(unsigned char r, unsigned char v)
{
  Wire.beginTransmission(I2C_ADDRESS);
  Wire.send(r);
  Wire.send(v);
  Wire.endTransmission();
}
 
unsigned char readRegister(unsigned char r)
{
  unsigned char v;
  Wire.beginTransmission(I2C_ADDRESS);
  Wire.send(r);  // register to read
  Wire.endTransmission();
 
  Wire.requestFrom(I2C_ADDRESS, 1); // read a byte
  while(!Wire.available()) {
    // waiting
  }
  v = Wire.receive();
  return v;
}

First of all we power up the LIS302DL and initialize it:

void setupLIS() {
 
  Serial.println("Setting up LIS302DL");
 
  pinMode(LIS302_POWER_PIN, OUTPUT); //the power pin
  pinMode(LIS302_INT2_PIN, INPUT); //the int2 pin
 
  digitalWrite(LIS302_POWER_PIN,LOW); //switch off the LIS302
 
  Wire.begin();        // join i2c bus (address optional for master)
 
}
 
void startLIS() {
 
  Serial.println("Powering up LIS302DL");
  digitalWrite(LIS302_POWER_PIN,HIGH); //switch off the LIS302
 
  delay(POWER_UP_DELAY);
  writeRegister(CTRL_REG1 , _BV(CTRL_PD) | _BV(CTRL_XEN) | _BV(CTRL_YEN) | _BV(CTRL_ZEN));
 
  //read who am i
  char myself = readRegister(REGISTER_WHO_AM_I);
  if (myself == WHO_AM_I_RESULT) {
    Serial.println("yippie got an lis302DL!");
  } else {
    Serial.print("found an ");
    Serial.print(myself, HEX);
    Serial.println("! very strange!");
  }
}

The routine setupLIS() does the basic initialization while startLIS() does everything to power it up (I put it in two routines since I thought I would write an power down routine – but this did not happen until now).
Most of the magic is in the routine

  writeRegister(CTRL_REG1 , _BV(CTRL_PD) | _BV(CTRL_XEN) | _BV(CTRL_YEN) | _BV(CTRL_ZEN));

It stops internal power down (CTRL_PD), and enables all three axis for detection. After this is done I check if the LIS302DL does correctly report to ‘who am I’ – register 0×0f. This is more or less an sanity check (as you can see by the diagnostic output).
After you have down the right initialization magic the readout is an charm:

  char x = readRegister(X_OUT);
  char y = readRegister(Y_OUT);
  char z = readRegister(Z_OUT);

Right now I just read it out every 100ms – you could of courser do it in a more sophisticated way by waiting until new data is ready by watching the status registers or using interrupts. But there is always something better to do. Perhaps I will add it later.

And before you ask how to do it yourself: Check the source code!

Related posts:

• Arduino & AD7746
• Arduino & Barometric Pressure Sensor BMP085
• Decoupling LIS302DL – There I fixed it!
• Tinkering with ADJD-S371-Q999

Tagged as: Accelerometer, Arduino, I2C, LIS302DL, Prototype, Sparkfun