Accelerometer LIS3DSH

LIS3DSH is an 3-axis MEMS accelerometer made by STMicroelectronics. Its full scale range is selectable from ±2g to ±16g. The size is small and it is only 3mm x 3mm. Either SPI or I²C can be used to interface with it. Supply voltage is from 1.71 V to 3.6 V. In this article, testing and evaluation of STEVAL-MKI134V1 adapter board is discussed.

Figure. STEVAL-MKI134V1 - LIS3DSH adapter board for standard DIL24 socket.

Its acceleration values are output in 16 bit digital numbers. The output data rate (ODR) can be up to 1600.
Resolution of its digital output
$$ \text{mg/digit} = \frac{2g - (-2g)}{2^{16}-1} = 61 \text{ } \mu \text{g} = 0.5966 \text{ mm s}^{-2} $$
where the gravity at Singapore is 9781 mm s^-2.
Therefore, its resolution due to its digitization is 61 μg/digit. In face, the actual sensitivity of the accelerometer (sensing resolution) depends on its noise floor. Its noise density as in the datasheet is 150 μg/sqrt(Hz). For a bandwidth of 100 Hz, its sensing resolution will be 1500 μg.
$$ An = {150} \times {\sqrt{BW}} = 1500 \text{ } \mu \text{g} = 14.67 \text{ mm s}^{-2} $$

Figure. Pin connection.

Using SPI Interface

An example schematic circuit diagram for LIS3DSH to use SPI interface is shown below. In this example, only 4-wires are used and interrupt is not utilized.

Figure. LIS3DSH electrical connection using SPI

In the following example, schematic and program for using LIS3DSH accelerometer with Arduino Uno through SPI interface is presented. Digital IO of Arduino Uno is 5V while that of LIS3DSH is 3.3V. Therefore, a bi-directional logic level converter is used to interface them. Schematic circuit diagram with STEVAL-MKI134V1 adapter board is shown below.

Figure. Schematic circuit diagram for STEVAL-MKI134V1 using SPI.

Figure. Wire connection for SPI.

SPI library for Arduino is used for Serial Peripheral Interface (SPI) - Mode 3, MSB first.

#include <SPI.h>
const int CS_Pin = 10;// set pin 10 as the chip select
SPISettings settingsA(2000000, MSBFIRST, SPI_MODE3); // set up the speed, data order and data mode
//SPI pin configuration: pin 11 as MOSI (SDI), pin 12 as MISO (SDO) , pin 13 as clock (SPC)

int x,y,z;
float K=0.061; // (4000/65535) milli-g per digit for +/-2g full scale using 16 bit digital output

void setup() {
  Serial.begin(9600);
  pinMode (CS_Pin, OUTPUT);  //Chip Select pin to control SPI
  digitalWrite(CS_Pin, HIGH);//Disable SPI
  SPI.begin();
  SPI.beginTransaction(settingsA);

  digitalWrite(CS_Pin, LOW);//Enable SPI
  SPI.transfer(0x20);//Send address of 'Control register 4' to write configuration
  SPI.transfer(0x7F);//Write a value that enables x,y,z accelerometers
  digitalWrite(CS_Pin, HIGH);//Disable SPI
}

void loop() {
  delay(1000);
  digitalWrite(CS_Pin, LOW);//Enable SPI
  SPI.transfer(0xA8);//Send address of LSB of x. Address is auto-increased after each reading.
  x = SPI.transfer(0) | SPI.transfer(0)<<8; //x acceleration 
  y = SPI.transfer(0) | SPI.transfer(0)<<8; //y acceleration
  z = SPI.transfer(0) | SPI.transfer(0)<<8; //z acceleration
  digitalWrite(CS_Pin, HIGH);//Disable SPI
  Serial.println("x=" + String(K*x)+" mg  \ty=" + String(K*y)+" mg  \tz=" + String(K*z)+" mg");
}

Using I2C Interface

I2C interface with LIS3DSH is shown below.

Figure. LIS3DSH electrical connection using I2C

As an example, a schematic and a program for using LIS3DSH accelerometer with Arduino Uno through I2C interface is presented. Normally, when a pin is configured as an I2C pin, it will be in open drain configuration and they can be just connected directly using a suitable pull-up resistor. But, in the case of Arduino UNO, A4 and A5 looks pulled up internally to 5V. That is why, a bi-directional logic level converter is used as a safety measure.

Figure. Schematic for bi-directional logic level converter.

Figure. Schematic circuit diagram for STEVAL-MKI134V1 using I2C.

Figure. Wire connection for I2C

For I2C (Inter-Integrated Circuit), Wire Library for Arduino is used.

#include <Wire.h>
int x,y,z;
float K=0.061; // (4000/65535) milli-g per digit for +/-2g full scale using 16 bit digital output
void setup()
{
  Wire.begin();        // join i2c bus (address optional for master)
  Serial.begin(9600);  // start serial for output
  Wire.beginTransmission(0x1E); // transmit to device #30
  Wire.write(0x20);//Send address of 'Control register 4' to write configuration
  Wire.write(0x7F);//Write a value that enables x,y,z accelerometers
  Wire.endTransmission();// stop transmitting
}

void loop()
{
  delay(1000);
  
  Wire.beginTransmission(0x1E); // transmit to device #30
  Wire.write(0x28);//Send address of LSB of x. Address is auto-increased after each reading.
  Wire.endTransmission();    // stop transmitting

  Wire.requestFrom(0x1E, 6);    // request 6 bytes from slave device #30
  x = Wire.read() | Wire.read()<<8; //x acceleration 
  y = Wire.read() | Wire.read()<<8; //y acceleration
  z = Wire.read() | Wire.read()<<8; //z acceleration
  
  Serial.println("x=" + String(K*x)+" mg  \ty=" + String(K*y)+" mg  \tz=" + String(K*z)+" mg");
}

A code sample for NXP LPC54102 dual core ARM microcontroller to read accelerometers and a gyroscope can be found at the following link together with the above examples.
Accelerometer_LIS3DSH_ADIS16003 on GitHub

Figure. A gyroscope and 4 accelerometers on the bottom side, and a dual core ARM microcontroller on top side of an in-house built embedded circuit board (Ø < 1 in).

Figure. An embedded inertial measurement unit using LPC54102 ARM microcontroller.

Uisg ADIS16003 accelerometer with AT89C51CC03 8051 microcontroller can also be found there too.