Small example on how to read input from a LIS331HH accelerometer chip, and then to use that input to replicate the orientation of the chip using a servo.

LIS331HH_example.ino

// Arduino UNO system clock speed: 16 MHz

// max SPI clock frequency: 10 MHz
// shift order: MSB first
// SPC idle level: HIGH
// data samples capture edge: rising

#include <SPI.h>
#include <Servo.h>

#define PIN_SLAVE_SELECT 10
#define PIN_SERVO_SIGNAL 2
#define SERVO_ANGLE_MAX 180
#define SERVO_ANGLE_MIN 0

// represent servo as an object
Servo myServo;

// maintain servo angle state, initialize in the middle of the range
int angle = (SERVO_ANGLE_MAX + SERVO_ANGLE_MIN) / 2;
#define ANGLE_TOLERANCE 2.0

// masks for read/write accesses
const byte MASK_READ = 0b10000000;
const byte MASK_WRITE = 0b00000000;

// register addresses

// control register 1 [rw]
// bits: PM2 | PM1 | PM0 | DR1 | DR0 | Zen | Yen | Xen

// PM2 - PM0:
//   Power mode selection. Default value: 000
//
//   BITS  Mode Select  Output data rate [Hz]
//   000   Power-down   --
//   001   Normal mode  ODR
//   010   Low-power    0.5
//   011   Low-power    1
//   100   Low-power    2
//   101   Low-power    5
//   110   Low-power    10

// DR1 - DR0:
//   In normal mode, select the data rate at which acceleration samples are produced.
//   In low-power mode, define output data resolution.
//
//   BITS  ODR  Low-pass filter cut-off frequency [Hz]
//   00    50   37
//   01    100  74
//   10    400  292
//   11    1000 780

// Zen/Yen/Xen:
//   X/Y/Z axis enable. Default value: 1 (0: axis enabled, 1: axis disabled)
const byte REG_CTRL_REG1 = 0b00100000;

const byte REG_CTRL_REG2 = 0b00100001;

const byte REG_CTRL_REG4 = 0b00100011;

// X-axis acceleration data. The value is expressed as two's complement.
const byte REG_OUT_X_L = 0b00101000;
const byte REG_OUT_X_H = 0b00101001;

// Y-axis acceleration data. The value is expressed as two's complement.
const byte REG_OUT_Y_L = 0b00101010;
const byte REG_OUT_Y_H = 0b00101011;

// Z-axis acceleration data. The value is expressed as two's complement.
const byte REG_OUT_Z_L = 0b00101100;
const byte REG_OUT_Z_H = 0b00101101;


void setup() {
  Serial.begin(115200);

  // set up servo
  myServo.attach(PIN_SERVO_SIGNAL);
  myServo.write(angle);

  // set up SPI communication
  pinMode(PIN_SLAVE_SELECT, OUTPUT);
  digitalWrite(PIN_SLAVE_SELECT, HIGH);

  SPI.begin();

  SPI.setBitOrder(MSBFIRST);
  SPI.setDataMode(SPI_MODE3);
  SPI.setClockDivider(SPI_CLOCK_DIV16);

  reboot();
  delay(100);

  // set up accelerometer
  setNormalMode();
  setHighPassFilterOff();
  setFullScale();
  delay(50);
}

void loop() {
  double x = readX();
  double z = readZ();
  double phi = constrain(90.0 + acos(-z / sqrt(x*x+z*z)) * ((x > 0) ? 360.0 : -360.0) / TWO_PI, 0.0, 180.0);

  if (abs(angle - phi) > ANGLE_TOLERANCE) {
    myServo.write(phi);
    angle = phi;
  }

  delay(10);
}

double readAccelerationRegister(byte address) {
  return (double(readRegister(address) | (readRegister(address + 1) << 8))
    + ((address == REG_OUT_X_L) ?   32.0000 : 0.0)
    + ((address == REG_OUT_Z_L) ? -149.3125 : 0.0)
    ) * 48.0 / 65535.0;
}

byte readRegister(byte address) {
  byte result;

  // call LIS331HH to attention
  digitalWrite(PIN_SLAVE_SELECT, LOW);

  SPI.transfer(MASK_READ | address);
  result = SPI.transfer(0);

  // release LIS331HH
  digitalWrite(PIN_SLAVE_SELECT, HIGH);

  return result;
}

byte readCtrl1() {
  return readRegister(REG_CTRL_REG1);
}

byte readCtrl2() {
  return readRegister(REG_CTRL_REG2);
}

double readX() {
  return readAccelerationRegister(REG_OUT_X_L);
}

double readY() {
  return readAccelerationRegister(REG_OUT_Y_L);
}

double readZ() {
  return readAccelerationRegister(REG_OUT_Z_L);
}

void reboot() {
  writeRegister(REG_CTRL_REG2, 0b10000000);
}

void setFullScale() {
  writeRegister(REG_CTRL_REG4, 0b10110000);
}

void setHighPassFilterOff() {
  writeRegister(REG_CTRL_REG2, 0b00000000);
}

void setNormalMode() {
  writeRegister(REG_CTRL_REG1, 0b00100111);
}

void writeRegister(byte address, byte flags) {
  // call LIS331HH to attention
  digitalWrite(PIN_SLAVE_SELECT, LOW);

  SPI.transfer(MASK_WRITE | address);
  SPI.transfer(flags);

  // release LIS331HH
  digitalWrite(PIN_SLAVE_SELECT, HIGH);  
}

I am doing this same project but with a stepper motor by chance you can show me your schematic?

my email is: ricardojcportugal@hotmail.com