Arduino

I2C Wiring

Use this wiring if you want to connect via I2C interface

By default, the i2c address is 0x5d.  If you add a jumper from SDO to GND, the address will change to 0x5c.

  • If you are running a 5V Arduino (Uno, etc.), connect Arduino 5V to board VIN
  • Connect Arduino GND to board GND
  • Connect Arduino SCL to board SCK
  • Connect Arduino SDA to board SDI

The final results should resemble the illustration above, showing an Adafruit Metro development board.

SPI Wiring

Since this is a SPI-capable sensor, we can use hardware or 'software' SPI. To make wiring identical on all microcontrollers, we'll begin with 'software' SPI. The following pins should be used:

  • Connect Vin to the power supply, 3V or 5V is fine. Use the same voltage that the microcontroller logic is based off of
  • Connect GND to common power/data ground
  • Connect the SCK pin to Digital #13 but any pin can be used later
  • Connect the SDO pin to Digital #12 but any pin can be used later
  • Connect the SDI pin to Digital #11 but any pin can be used later
  • Connect the CS pin Digital #10 but any pin can be used later

Later on, once we get it working, we can adjust the library to use hardware SPI if you desire, or change the pins to others.

Library Installation

You can install the Adafruit LPS35HW Library for Arduino using the Library Manager in the Arduino IDE:

Click the Manage Libraries ... menu item, search for Adafruit LPS35HW, and select the Adafruit LPS35HW library:

Then follow the same process for the Adafruit BusIO library.

Load Example

Open up File -> Examples -> Adafruit LPS35HW -> lps35hw_test and upload to your Arduino wired up to the sensor.

Depending on whether you are using I2C or SPI, change the pin names and comment or uncomment the following lines.

Download: file
if (!lps35hw.begin_I2C()) {
  //if (!lps35hw.begin_SPI(LPS_CS)) {
  //if (!lps35hw.begin_SPI(LPS_CS, LPS_SCK, LPS_MISO, LPS_MOSI)) {

Once you upload the code, you will see the temperature and pressure being printed when you open the Serial Monitor (Tools->Serial Monitor) at 9600 baud, similar to this:

Temperature is calculated in degrees C, you can convert this to F by using the classic F = C * 9/5 + 32 equation.

Pressure is returned in the SI units of Pascals. 100 Pascals = 1 hPa = 1 millibar. Often times barometric pressure is reported in millibar or inches-mercury. For future reference 1 pascal =0.000295333727 inches of mercury, or 1 inch Hg = 3386.39 Pascal. So if you take the pascal value of say 100734 and divide by 3386.39 you'll get 29.72 inches-Hg.

Example Code

The following example code is part of the standard library, and illustrates how you can retrieve sensor data from the LPS35HW for pressure and temperature:

#include <Adafruit_LPS35HW.h>

Adafruit_LPS35HW lps35hw = Adafruit_LPS35HW();

// For SPI mode, we need a CS pin
#define LPS_CS  10
// For software-SPI mode we need SCK/MOSI/MISO pins
#define LPS_SCK  13
#define LPS_MISO 12
#define LPS_MOSI 11

void setup() {
  Serial.begin(115200);
  // Wait until serial port is opened
  while (!Serial) { delay(1); }

  Serial.println("Adafruit LPS35HW Test");

  if (!lps35hw.begin_I2C()) {
  //if (!lps35hw.begin_SPI(LPS_CS)) {
  //if (!lps35hw.begin_SPI(LPS_CS, LPS_SCK, LPS_MISO, LPS_MOSI)) {
    Serial.println("Couldn't find LPS35HW chip");
    while (1);
  }
  Serial.println("Found LPS35HW chip");
}

void loop() {
  Serial.print("Temperature: ");
  Serial.print(lps35hw.readTemperature());
  Serial.println(" C");
  
  Serial.print("Pressure: ");
  Serial.print(lps35hw.readPressure());
  Serial.println(" hPa");

  Serial.println();
  delay(1000);
}
This guide was first published on Jun 11, 2019. It was last updated on Jun 11, 2019. This page (Arduino) was last updated on Sep 22, 2019.