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Arduino

Micro:bit and HDC2080 sensor example using the Arduino IDE

by shedboy71

In this article we look at yet another humidity and temperature sensor from TI – this time its the HDC2080 which we will connect up to a Micro:bit

Lets look at some of the technical information and data from TI

HDC2080 Information

The HDC2080 device is an integrated humidity and temperature sensor that provides high accuracy measurements with very low power consumption in a small DFN package. The capacitive-based sensor includes new integrated digital features and a heating element to dissipate condensation and moisture. The HDC2080 digital features include programmable interrupt thresholds to provide alerts and system wake-ups without requiring a microcontroller to be continuously monitoring the system. Combined with programmable sampling intervals, a low power consumption, and a support for a 1.8-V supply voltage, the HDC2080 is designed for battery-operated systems.

The HDC2080 provides high accuracy measurement capability for a wide range of environmental monitoring and Internet of Things (IoT) applications such as smart thermostats and smart home assistants. For designs where printed-circuit board (PCB) area is critical, a smaller CSP package option is available thru the HDC2010 with complete software compatibility with the HDC2080.

For applications with strict power-budget restrictions, Auto Measurement Mode enables the HDC2080 to automatically initiate temperature and humidity measurements. This feature allows users to configure a microcontroller into deep sleep mode because the HDC2080 is no longer dependent upon the microcontroller to initiate a measurement.

Programable temperature and humidity thresholds in the HDC2080 allow the device to send a hardware interrupt to wake up the microcontroller when necessary. In addition, the power consumption of the HDC2080 is significantly reduced, which helps to minimize self-heating and improve measurement accuracy.

The HDC2080 is factory-calibrated to 0.2°C temperature accuracy and 2% relative humidity accuracy.

Features

Relative humidity range: 0% to 100%
Humidity accuracy: ±2% (typical), ±3% (maximum)
Temperature accuracy: ±0.2°C (typical), ±0.4°C (maximum)
Sleep mode current: 50 nA (typical), 100 nA (maximum)
Average supply current (1 measurement/second)
300 nA: RH% only (11 bit)
550 nA: RH% (11 bit) + temperature (11 bit)

Temperature range:
Operating: –40°C to 85°C
Functional: –40°C to 125°C
Supply voltage range: 1.62 V to 3.6 V

 

Parts Required

I connected a expansion board to a Micro:bit and then the sensor via connecting wire

Name Link
Micro:bit
HDC2080 HDC2080 Temperature and Humidity Low Power Digital I2C Sensor
Connecting wire Free shipping Dupont line 120pcs 20cm male to male + male to female and female to female jumper wire
expansion board

Schematic/Connection

This is a 3.3v rated sensor even though the pin says Vcc

microbit and hdc2080

microbit and hdc2080

Code Example

I used the library from https://github.com/tinkeringtech/HDC2080_breakout

This is the default example with a few cosmetic changes

[codesyntax lang=”cpp”]

#include <HDC2080.h>

#define ADDR 0x40
HDC2080 sensor(ADDR);

float temperature = 0, humidity = 0;

void setup() {

  Serial.begin(9600);
  Serial.println("TinkeringTech HDC2080 Test");

  // Initialize I2C communication
  sensor.begin();
    
  // Begin with a device reset
  sensor.reset();
  
  // Set up the comfort zone
  sensor.setHighTemp(48);         // High temperature of 28C
  sensor.setLowTemp(2);          // Low temperature of 22C
  sensor.setHighHumidity(95);     // High humidity of 55%
  sensor.setLowHumidity(10);      // Low humidity of 40%
  
  // Configure Measurements
  sensor.setMeasurementMode(TEMP_AND_HUMID);  // Set measurements to temperature and humidity
  sensor.setRate(ONE_HZ);                     // Set measurement frequency to 1 Hz
  sensor.setTempRes(FOURTEEN_BIT);
  sensor.setHumidRes(FOURTEEN_BIT);
  
  //begin measuring
  sensor.triggerMeasurement();
}

void loop() {

  Serial.print("Temperature (C): "); 
  Serial.print(sensor.readTemp());
  Serial.print("\t\tHumidity (%): "); 
  Serial.println(sensor.readHumidity());
  
  // Wait 1 second for the next reading
  delay(2000);
  
}

[/codesyntax]

 

Output

Open the serial monitor and you should see something like this

Temperature (C): 21.42 Humidity (%): 43.31
Temperature (C): 21.42 Humidity (%): 43.32
Temperature (C): 21.42 Humidity (%): 43.35
Temperature (C): 21.42 Humidity (%): 43.33
Temperature (C): 21.73 Humidity (%): 42.86
Temperature (C): 24.37 Humidity (%): 45.18
Temperature (C): 25.30 Humidity (%): 49.11
Temperature (C): 25.90 Humidity (%): 53.62
Temperature (C): 26.44 Humidity (%): 57.36
Temperature (C): 26.94 Humidity (%): 60.30
Temperature (C): 27.17 Humidity (%): 65.88
Temperature (C): 26.42 Humidity (%): 63.08

 

Links

https://www.ti.com/lit/gpn/hdc2080

 

Summary

A nice little sensor but at just over $8 there are cheaper sensors available which have the same functionality.

Arduino

Micro:bit and BH1745NUC Luminance and Colour Sensor example using the Arduino IDE

by shedboy71

In this article we look at a BH1745NUC Luminance and Colour Sensor and connect it to a Micro:bit

Lets have a look at the sensor

The BH1745NUC is digital color sensor IC with I²C bus interface. This IC senses Red, Green and Blue light (RGB) and converts them to digital values. The high sensitivity, wide dynamic range and excellent Ircut characteristics makes this IC the most suitable to obtain the illuminance and color temperature of ambient light for adjusting LCD backlight of TV, mobile phone and tablet PC. It is possible to detect very wide range light intensity. (0.005 – 40k lx)

Specifications:

VCC Voltage Range: 2.3V to 3.6V
Maximum Sensitivity: 0.005Lx/step
Current Consumption: 130μA (Typ)
Standby Mode Current: 0.8μA (Typ)
Operating Temperature Range: -40°C to +85°C

Features

The High Sensitivity and Wide Dynamic Range (0.005 – 40k lx)
Supports Low Transmittance (Dark) Window
Correspond to I²C Bus Interface
Low Current by Power Down Function
Rejecting 50Hz/60Hz Light Noise
Correspond to 1.8V Logic Interface
Programmable Interrupt Function
It is possible to select 2 type of I²C bus slave address (ADDR =’L’: “0111000”, ADDR =’H’: “0111001”)

Here is a typical module that I used

 

 

Parts Required

I connected a sensor shield to an Arduino and then the sensor via connecting wire

Name Link
Micro:bit Micro Bit Development Board
BH1745NUC BH1745NUC Digital Color Sensor RGB Detecting Sensor Light Module
Connecting wire Free shipping Dupont line 120pcs 20cm male to male + male to female and female to female jumper wire
Expansion Board GPIO Expansion Board For micro:bit

 

Schematic/Connection

Be careful as I used a CJMCU-1745 – the sensor is rated at 2.3V to 3.6V. So use the 3.3v out

 

microbit Sensor
3.3v VIN
Gnd Gnd
SDA SDA
SCL SCL

Code Example

 

This is a controleverything example – they have code examples for various platforms

[codesyntax lang=”cpp”]

#include <Wire.h>

// I2C address of the BH1745NUC
#define Addr 0x38

void setup()
{
    // Initialise I2C communication as MASTER
    Wire.begin();
    // Initialise serial communication, set baud rate = 9600
    Serial.begin(9600);

    // Start I2C Transmission
    Wire.beginTransmission(Addr);
    // Select mode control register1
    Wire.write(0x41);
    // Set RGBC measurement time 160 msec
    Wire.write(byte(0x00));
    // Stop I2C Transmission
    Wire.endTransmission();
    
    // Start I2C Transmission
    Wire.beginTransmission(Addr);
    // Select mode control register2
    Wire.write(0x42);
    // Set measurement mode is active, gain = 1x
    Wire.write(0x90);
    // Stop I2C Transmission
    Wire.endTransmission();
    
    // Start I2C Transmission
    Wire.beginTransmission(Addr);
    // Select mode control register3
    Wire.write(0x44);
    // Set default value
    Wire.write(0x02);
    // Stop I2C Transmission
    Wire.endTransmission();
    delay(300);
}

void loop()
{
    unsigned int data[8];
    for(int i = 0; i < 8; i++)
    {
        // Start I2C Transmission
        Wire.beginTransmission(Addr);
        // Select data register
        Wire.write((80+i));
        // Stop I2C Transmission
        Wire.endTransmission();
        
        // Request 1 byte of data from the device
        Wire.requestFrom(Addr, 1);
        
        // Read 8 bytes of data
        // Red lsb, Red msb, Green lsb, Green msb, Blue lsb, Blue msb
        // cData lsb, cData msb
        if(Wire.available() == 1)
        {
            data[i] = Wire.read();
        }
        delay(300);
    }

    // Convert the data
    int red = ((data[1] & 0xFF) * 256) + (data[0] & 0xFF);
    int green = ((data[3] & 0xFF) * 256) + (data[2] & 0xFF);
    int blue = ((data[5] & 0xFF) * 256) + (data[4] & 0xFF);
    int cData = ((data[7] & 0xFF) * 256) + (data[6] & 0xFF);
    
    // Output data to serial monitor
    Serial.print("Red Color luminance  : ");
    Serial.println(red);
    Serial.print("Green Color luminance : ");
    Serial.println(green);
    Serial.print("Blue Color luminance : ");
    Serial.println(blue);
    Serial.print("Clear Data Color luminance : ");
    Serial.println(cData);
}

[/codesyntax]

 

Output

Open the serial monitor and you should see something like the following

 

Place different colored objects beside the sensor and check the values

Arduino

Micro:bit and BMM150 digital geomagnetic sensor example using the Arduino IDE

by shedboy71

In this article we look at a digital geomagnetic sensor – this time its the BMM150. We will connect this to a micro:bit and use the Arduino IDE for development

BMM150 is a low power and low noise 3-axis digital geomagnetic sensor to be used in compass applications. The 12-pin wafer level chip scale package (WLCSP) with a footprint of 1.56 x 1.56 mm² and 0.60 mm height provides highest design flexibility to the developer of mobile devices. Applications like virtual reality or gaming on mobile devices such as mobile phones, tablet PCs or portable media players require 9-axis inertial sensing including magnetic heading information. Due to the stable performance over a large temperature range, the BMM150 is also especially suited for supporting drones in accurate heading.

BMM150 can be used with an inertial measurement unit (IMU) consisting of a 3-axis accelerometer and a 3-axis gyroscope like Bosch Sensortec’s BMI055.

 

Features

Parameter Technical data
Package CSWLP- (12 pin)
1.56×1.56×0.6 mm³
0.4 mm diagonal ball pitch
Temperature range -40°C … +85°C
Digital interfaces I²C and SPI
(2 interrupt pins)
Resolution 0.3μT
Supply voltage VDD: 1.62V to 3.6V
VDDIO: 1.2V to 3.6V
Zero-B offset ±50μT
Non-linearity <1% FS
Magnetic range typ. ±1300μT (x,y-axis)
±2500μT (z-axis)
Average current consumption 170 μA (low power preset)
500 μA (normal mode)
Interrupts New data, magnetic threshold high / low

Parts Required

I use an expansion board which slots into the micro:bit, I find this easier to connect wires to a sensor. Here is a picture of an expansion board.

Name Link
Microbit Micro Bit Development Board, Microbit, NRF51822 Master Card, Phython Graphic Programming
BMM150 BMM150 Geomagnetic Sensor Breakout Board
Connecting wire Free shipping Dupont line 120pcs 20cm male to male + male to female and female to female jumper wire
GPIO Expansion Board GPIO Expansion Board For micro:bit

Schematic/Connection

 

microbit and bmm150 bb

microbit and bmm150 bb

 

Code Example

This uses the library from https://github.com/Seeed-Studio/Grove_3_Axis_Compass_V2.0_BMM150

[codesyntax lang=”cpp”]

#include <Arduino.h>
#include <Wire.h>
// libraries
#include “bmm150.h”
#include “bmm150_defs.h”

BMM150 bmm = BMM150();

void setup()
{
Serial.begin(9600);

if(bmm.initialize() == BMM150_E_ID_NOT_CONFORM) {
Serial.println(“Chip ID can not read!”);
while(1);
} else {
Serial.println(“Initialize done!”);
}

}

void loop()
{
bmm150_mag_data value;
bmm.read_mag_data();

value.x = bmm.raw_mag_data.raw_datax;
value.y = bmm.raw_mag_data.raw_datay;
value.z = bmm.raw_mag_data.raw_dataz;

float xyHeading = atan2(value.x, value.y);
float zxHeading = atan2(value.z, value.x);
float heading = xyHeading;

if(heading < 0)
heading += 2*PI;
if(heading > 2*PI)
heading -= 2*PI;
float headingDegrees = heading * 180/M_PI;
float xyHeadingDegrees = xyHeading * 180 / M_PI;
float zxHeadingDegrees = zxHeading * 180 / M_PI;

Serial.print(“Heading: “);
Serial.println(headingDegrees);

delay(100);
}

[/codesyntax]

Output

Open the serial monitor and you should see something like this

Heading: 3.60
Heading: 11.57
Heading: 22.33
Heading: 30.79
Heading: 45.00
Heading: 68.20
Heading: 152.02
Heading: 183.25
Heading: 192.01
Heading: 192.46
Heading: 202.32

 

Links

https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST-BMM150-DS001.pdf

https://github.com/BoschSensortec/BMM150-Sensor-API

 

Arduino

Micro:bit and MMA8452 accelerometer example

by shedboy71

In this example we will connect a MMA8452Q accelerometer  to a Microbit – we will be using the Arduino IDE

Lets look at some information about the sensor

The MMA8452Q is a smart, low-power, three-axis, capacitive, micromachined accelerometer with 12 bits of resolution. This accelerometer is packed with embedded functions with flexible user programmable options, configurable to two interrupt pins. Embedded interrupt functions allow for overall power savings relieving the host processor from continuously polling data.

The MMA8452Q has user selectable full scales of ±2 g/±4 g/±8 g with high-pass filtered data as well as non-filtered data available real-time. The device can be configured to generate inertial wakeup interrupt signals from any combination of the configurable embedded functions allowing the MMA8452Q to monitor events and remain in a low-power mode during periods of inactivity

 

Connection

Here is a layout, its an easy device to connect

microbit and mma8452

microbit and mma8452

Parts List

Here are the parts I used

Part name Link
Micro:bit Micro:bit Development Board
Edge Breakout I/O Expansion Edge Breakout I/O Expansion Extension Board for BBC micro:bit
MMA8452 sensor GY-45 MMA8452 Module Digital Triaxial Accelerometer Precision Tilt 3-Axis
Dupont cable Free shipping Dupont line 120pcs 20cm male to male + male to female and female to female jumper wire Dupont cablefor Arduino

 

Code

There is a library from sparkfun but there is this example which does not require any libraries

[codesyntax lang=”cpp”]

// Distributed with a free-will license.
// Use it any way you want, profit or free, provided it fits in the licenses of its associated works.
// MMA8452Q
// This code is designed to work with the MMA8452Q_I2CS I2C Mini Module available from ControlEverything.com.
// https://www.controleverything.com/content/Accelorometer?sku=MMA8452Q_I2CS#tabs-0-product_tabset-2

#include <Wire.h>

// MMA8452Q I2C address is 0x1C(28)
#define Addr 0x1C

void setup()
{
  // Initialise I2C communication as MASTER
  Wire.begin();
  // Initialise Serial Communication, set baud rate = 9600
  Serial.begin(9600);

  // Start I2C Transmission
  Wire.beginTransmission(Addr);
  // Select control register
  Wire.write(0x2A);
  // StandBy mode
  Wire.write((byte)0x00);
  // Stop I2C Transmission
  Wire.endTransmission();

  // Start I2C Transmission
  Wire.beginTransmission(Addr);
  // Select control register
  Wire.write(0x2A);
  // Active mode
  Wire.write(0x01);
  // Stop I2C Transmission
  Wire.endTransmission();

  // Start I2C Transmission
  Wire.beginTransmission(Addr);
  // Select control register
  Wire.write(0x0E);
  // Set range to +/- 2g
  Wire.write((byte)0x00);
  // Stop I2C Transmission
  Wire.endTransmission();
  delay(300);
}

void loop()
{
  unsigned int data[7];

  // Request 7 bytes of data
  Wire.requestFrom(Addr, 7);
  
  // Read 7 bytes of data
  // staus, xAccl lsb, xAccl msb, yAccl lsb, yAccl msb, zAccl lsb, zAccl msb
  if(Wire.available() == 7) 
  {
    data[0] = Wire.read();
    data[1] = Wire.read();
    data[2] = Wire.read();
    data[3] = Wire.read();
    data[4] = Wire.read();
    data[5] = Wire.read();
    data[6] = Wire.read();
  }

  // Convert the data to 12-bits
  int xAccl = ((data[1] * 256) + data[2]) / 16;
  if (xAccl > 2047)
  {
    xAccl -= 4096;
  }
    
  int yAccl = ((data[3] * 256) + data[4]) / 16;
  if (yAccl > 2047)
  {
    yAccl -= 4096;
  }
    
  int zAccl = ((data[5] * 256) + data[6]) / 16;
  if (zAccl > 2047)
  {
    zAccl -= 4096;
  }

  // Output data to serial monitor
  Serial.print("Acceleration in X-Axis : ");
  Serial.println(xAccl);
  Serial.print("Acceleration in Y-Axis : ");
  Serial.println(yAccl);
  Serial.print("Acceleration in Z-Axis : ");
  Serial.println(zAccl);
  delay(500);
}

[/codesyntax]

Output

Open the serial monitor – this is what you should expect to see

Acceleration in X-Axis : 344
Acceleration in Y-Axis : 767
Acceleration in Z-Axis : -410
Acceleration in X-Axis : -789
Acceleration in Y-Axis : 222
Acceleration in Z-Axis : 243
Acceleration in X-Axis : -282
Acceleration in Y-Axis : -612
Acceleration in Z-Axis : -703
Acceleration in X-Axis : -1175
Acceleration in Y-Axis : 750
Acceleration in Z-Axis : -594

 

Links

https://www.nxp.com/docs/en/data-sheet/MMA8452Q.pdf

Arduino

Micro:bit and PCF8575 I/O expander examples

by shedboy71

This 16-bit I/O expander for the two-line bidirectional bus (I2C) is designed for 2.5-V to 5.5-V VCC operation.

The PCF8575 device provides general-purpose remote I/O expansion for most microcontroller families by way of the I2C interface [serial clock (SCL), serial data (SDA)].

The device features a 16-bit quasi-bidirectional input/output (I/O) port (P07–P00, P17–P10), including latched outputs with high-current drive capability for directly driving LEDs. Each quasi-bidirectional I/O can be used as an input or output without the use of a data-direction control signal. At power on, the I/Os are high. In this mode, only a current source to VCC is active.

Features

  • I2C to Parallel-Port Expander
  • Open-Drain Interrupt Output
  • Low Standby-Current Consumption of 10 µA Max
  • Compatible With Most Microcontrollers
  • 400-kHz Fast I2C Bus
  • Address by Three Hardware Address Pins for Use of up to Eight Devices
  • Latched Outputs With High-Current Drive Capability for Directly Driving LEDs

 

Connection

 

 

Parts List

Part Link
Micro:bit Micro:bit Development Board
Edge Breakout I/O Expansio Edge Breakout I/O Expansion Extension Board for BBC micro:bit
Dupont cable Free shipping Dupont line 120pcs 20cm male to male + male to female and female to female jumper wire
PCF8575 PCF8575 IIC I2C I/O Extension Shield Module 16 bit SMBus I/O

 

Code examples

Output – switch LED on and off

[codesyntax lang=”cpp”]

#include <Wire.h>

// Set I2C address
int address = 0x20;

void setup()
{ 
  Wire.begin();
  // Set all ports as output
  pf575_write(word(B11111111,B11111111));
} 

void loop()
{
  // Set port P0 on
  pf575_write(word(B00000000,B00000001));
  delay(1000);
  // Set port P0 off
  pf575_write(word(B00000000,B00000000));
  delay(1000);
} 

// Function for writing two Bytes to the I2C expander device
void pf575_write(uint16_t data) 
{
  Wire.beginTransmission(address);
  Wire.write(lowByte(data));
  Wire.write(highByte(data));
  Wire.endTransmission();
}

[/codesyntax]

 

Output – switch LEDs on and off

[codesyntax lang=”cpp”]

#include <Wire.h>
 
byte address = 0x20;   // address of PCF8575
 
void setup()
{
   Wire.begin();       // join i2c bus as master
}
 
 
void loop()
{
  unsigned char x;
  unsigned char y;
 
  for (x=0, y=255; (x+y)==255; x++, y--)
  {
      Wire.beginTransmission(address);   // send the address and the write cmnd
      Wire.write(x);                      // pack the first byte
      Wire.write(y);                      // pack the second byte
      Wire.endTransmission();            // send the data
      delay(150);     
   }
}

[/codesyntax]

Arduino

Micro:bit and LM75 temperature sensor example

by shedboy71

The LM75 temperature sensor includes a delta-sigma analog-to-digital converter, and a digital overtemperature detector. The host can query the LM75 through its I²C interface to read temperature at any time. The open-drain overtemperature output (OS) sinks current when the programmable temperature limit is exceeded.

The OS output operates in either of two modes, comparator or interrupt. The host controls the temperature at which the alarm is asserted (TOS) and the hysteresis temperature below which the alarm condition is not valid (THYST). Also, the LM75’s TOS and THYST registers can be read by the host.

The address of the LM75 is set with three pins to allow multiple devices to work on the same bus. Power-up is in comparator mode, with defaults of TOS = +80°C and THYST = +75°C. The 3.0V to 5.5V supply voltage range, low supply current, and I²C interface make the LM75 ideal for many applications in thermal management and protection.

Key Features

SO (SOP) and µMAX® (µSOP) Packages
I²C Bus Interface
Separate Open-Drain OS Output Operates as Interrupt or Comparator/Thermostat Input
Register Readback Capability
Power-Up Defaults Permit Stand-Alone Operation as a Thermostat
3.0V to 5.5V Supply Voltage
Low Operating Supply Current 250µA (typ), 1mA (max)
4µA (typ) Shutdown Mode Minimizes Power Consumption
Up to Eight LM75s Can Be Connected to a Single Bus

 

Parts List

name Link
Micro:bit Micro:bit Development Board
LM75 LM75A Temperature Sensor I2C Interface Temperature Module
connecting wire Free shipping Dupont line 120pcs 20cm male to male + male to female and female to female jumper wire

Layout

LM75 sensor Micro:bit
SDA 20 (SDA)
SCL 19 (SCL)
Vcc 3v
Gnd GND
DS N/C

 

Code

I used this library – https://github.com/thefekete/LM75

[codesyntax lang=”cpp”]

#include <Wire.h>
#include <LM75.h>

LM75 sensor;  // initialize an LM75 object
// You can also initiate with another address as follows:
//LM75 sensor(LM75_ADDRESS | 0b001);  // if A0->GND, A1->GND and A2->Vcc

void setup()
{
  Wire.begin();
  Serial.begin(9600);
}

void loop()
{
  // get temperature from sensor
  Serial.print("Current temp: ");
  Serial.print(sensor.temp());
  Serial.println(" C");
  
  // Tos Set-point
  sensor.tos(47.5); // set at 47.5'C
  Serial.print("Tos set at ");
  Serial.print(sensor.tos());
  Serial.println(" C");
  
  // Thyst Set-point
  sensor.thyst(42); // set at 42'C
  Serial.print("Thyst set at ");
  Serial.print(sensor.thyst());
  Serial.println(" C");
  
  // shutdown the sensor and wait a while
  sensor.shutdown(true);
  delay(3000);
  // wake up sensor for next time around
  sensor.shutdown(false);
  
  Serial.println();
}

[/codesyntax]

Output

Open the serial monitor

Current temp: 19.00 C
Tos set at 47.50 C
Thyst set at 42.00 C

Current temp: 18.87 C
Tos set at 256.00 C
Thyst set at 256.00 C

Current temp: 256.00 C
Tos set at 256.00 C
Thyst set at 42.00 C

Links

LM75 temperature sensor high speed I2C interface high precision development board module

Arduino

Micro:bit and GY-21P module example

by shedboy71

The GY-21P is an interesting module in that it combines a BMP280 sensor and an SI7021 sensor. The on-board BMP280+SI7021 sensor measures atmospheric pressure from 30kPa to 110kPa as well as relative humidity and temperature.

BMP280
Pressure range: 300-1100 hPa (9000 meters above sea level at -500m)
Relative accuracy (at 950 – 1050 hPa at 25 ° C): ± 0.12 hPa, equiv. to ± 1 m
Absolute accuracy (at (950 – 1050 hPa, 0 – +40 ° C): ± 0.12 hPa, equiv. To ± 1 m
Mains voltage: 1.8V – 3.6V
Power consumption: 2.7µA at 1Hz readout rate
Temperature range: -40 to + 85 ° C

SI7021
HVAC/R
Thermostats/humidistats
Respiratory therapy
White goods
Indoor weather stations
Micro-environments/data centers
Automotive climate control and defogging
Asset and goods tracking
Mobile phones and tablets
Size: 1.3*1cm/0.51*0.39″

Features:

Operation Voltage: 3.3V
I2C & SPI Communications Interface
Temp Range: -40C to 85C
Humidity Range: 0 – 100% RH, =-3% from 20-80%
Pressure Range: 30,000Pa to 110,000Pa, relative accuracy of 12Pa, absolute accuracy of 100Pa
Altitude Range: 0 to 30,000 ft (9.2 km), relative accuracy of 3.3 ft (1 m) at sea level, 6.6 (2 m) at 30,000 ft.

Parts List

name Link
Micro:bit Micro:bit Development Board
GY-21p module Atmospheric Humidity Temperature Sensor Breakout Barometric Pressure BMP280 SI7021 for Arduino GY-21P
connecting wire Free shipping Dupont line 120pcs 20cm male to male + male to female and female to female jumper wire

 

Code

I use a variety of Adafruit libraries, took the default examples and made the following out of them

https://github.com/adafruit/Adafruit_Sensor

https://github.com/adafruit/Adafruit_BMP280_Library

https://github.com/adafruit/Adafruit_Si7021

 

 

[codesyntax lang=”cpp”]

#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BMP280.h>
#include "Adafruit_Si7021.h"

Adafruit_BMP280 bme; // I2C
Adafruit_Si7021 sensor = Adafruit_Si7021();

void setup() 
{
Serial.begin(9600);
Serial.println("BMP280 and SI7021 (GY-21p) test");

if (!bme.begin()) 
{ 
Serial.println("Could not find a valid BMP280 sensor, check wiring!");
while (1);
}

if (!sensor.begin()) 
{
Serial.println("Did not find Si7021 sensor!");
while (true);
}
}

void loop() 
{
Serial.println("BMP280 results");
Serial.print("Temperature = ");
Serial.print(bme.readTemperature());
Serial.println(" *C");
Serial.print("Pressure = ");
Serial.print(bme.readPressure());
Serial.println(" Pa");
Serial.print("Approx altitude = ");
Serial.print(bme.readAltitude(1013.25)); // this should be adjusted to your local forcase
Serial.println(" m");
Serial.println();

Serial.println("SI7021 results");
Serial.print("Humidity: "); 
Serial.println(sensor.readHumidity(), 2);
Serial.print("Temperature: "); 
Serial.println(sensor.readTemperature(), 2);
Serial.println();
delay(2000);
}

[/codesyntax]

 

Output

OPen the serial monitor

BMP280 results
Temperature = 27.26 *C
Pressure = 99042.63 Pa
Approx altitude = 191.78 m

SI7021 results
Humidity: 31.04
Temperature: 27.30

BMP280 results
Temperature = 28.43 *C
Pressure = 99044.82 Pa
Approx altitude = 191.60 m

SI7021 results
Humidity: 32.59
Temperature: 28.56

BMP280 results
Temperature = 28.17 *C
Pressure = 99037.41 Pa
Approx altitude = 192.22 m

SI7021 results
Humidity: 32.88
Temperature: 28.46

You can see the temperature output is close between the sensors

 

Links

Atmospheric Humidity Temperature Sensor Breakout Barometric Pressure BMP280 SI7021 for Arduino

Arduino

Micro:bit and BMP280 barometric pressure sensor example

by shedboy71

BMP280 is an absolute barometric pressure sensor especially designed for mobile applications. The sensor module is housed in an extremely compact package. Its small dimensions and its low power consumption allow for the implementation in battery powered devices such as mobile phones, GPS modules or watches.

As its predecessor BMP180, BMP280 is based on Bosch’s proven Piezo-resistive pressure sensor technology featuring high accuracy and linearity as well as long term stability and high EMC robustness. Numerous device operation options offer highest flexibility to optimize the device regarding power consumption, resolution and filter performance. A tested set of default settings for example use case is provided to the developer in order to make design-in as easy as possible.

Applications

– Enhancement of GPS navigation (e.g. time-tofirst-fix improvement, dead-reckoning, slope detection)

– Indoor navigation (floor detection, elevator detection)

– Outdoor navigation, leisure and sports applications

– Weather forecast

– Health care applications (e.g. spirometry)

– Vertical velocity indication (e.g. rise/sink speed)

Parameter Technical data
Operation range (full accuracy) Pressure: 300…1100 hPa
Temperature: -40…85°C
Absolute accuracy
(Temp. @ 0…+65°C)		 ~ ±1 hPa
Relative accuracy
p = 700…900hPa
(Temp. @ +25…+40°C)		 ± 0.12 hPa (typical)
equivalent to ±1 m
Average current consumption (1 Hz data refresh rate) 2.74 μA, typical
(ultra-low power mode)
Average current consumption in sleep mode 0.1 μA
Average measurement time 5.5 msec
(ultra-low power preset)
Supply voltage VDDIO 1.2 … 3.6 V
Supply voltage VDD 1.71 … 3.6 V
Resolution of data Pressure: 0.01 hPa ( < 10 cm)
Temperature: 0.01° C
Temperature coefficient offset
(+25°…+40°C @900hPa)		 ± 0.12 hPa (typical)
equivalent to ±1 m
Interface I²C and SPI

Parts List

name Link
Micro:bit Micro:bit Development Board
GY-21p module Atmospheric Humidity Temperature Sensor Breakout Barometric Pressure BMP280 SI7021 for Arduino GY-21P
connecting wire Free shipping Dupont line 120pcs 20cm male to male + male to female and female to female jumper wire

Layout

This is a layout diagram using an adafruit part, my module had clearly marked SDA and SCL connections

microbit and bmp280

microbit and bmp280

 

Code

This example requires https://github.com/adafruit/Adafruit_BMP280_Library and https://github.com/adafruit/Adafruit_Sensor

 

[codesyntax lang=”cpp”]

/***************************************************************************
This is a library for the BMP280 humidity, temperature & pressure sensor

Designed specifically to work with the Adafruit BMEP280 Breakout
----> http://www.adafruit.com/products/2651

These sensors use I2C or SPI to communicate, 2 or 4 pins are required
to interface.

Adafruit invests time and resources providing this open source code,
please support Adafruit andopen-source hardware by purchasing products
from Adafruit!

Written by Limor Fried & Kevin Townsend for Adafruit Industries.
BSD license, all text above must be included in any redistribution
***************************************************************************/

#include <Wire.h>
#include <SPI.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BMP280.h>

Adafruit_BMP280 bme; // I2C


void setup() {
Serial.begin(9600);
Serial.println(F("BMP280 test"));

if (!bme.begin()) {
Serial.println("Could not find a valid BMP280 sensor, check wiring!");
while (1);
}
}

void loop() {
Serial.print("Temperature = ");
Serial.print(bme.readTemperature());
Serial.println(" *C");

Serial.print("Pressure = ");
Serial.print(bme.readPressure());
Serial.println(" Pa");

Serial.print("Approx altitude = ");
Serial.print(bme.readAltitude(1013.25)); // this should be adjusted to your local forcase
Serial.println(" m");

Serial.println();
delay(2000);
}

[/codesyntax]

 

Output

Open the serial monitor and you should see something like this – I sometimes get strange altitude readings – negative values, not sure why

Temperature = 27.65 *C
Pressure = 100592.44 Pa
Approx altitude = 61.17 m

Temperature = 28.72 *C
Pressure = 100589.25 Pa
Approx altitude = 61.44 m

Temperature = 29.31 *C
Pressure = 100590.25 Pa
Approx altitude = 61.35 m

Temperature = 29.70 *C
Pressure = 100588.21 Pa
Approx altitude = 61.53 m

Temperature = 30.01 *C
Pressure = 100581.49 Pa
Approx altitude = 62.09 m

Temperature = 28.95 *C
Pressure = 100601.21 Pa
Approx altitude = 60.44 m

 

Link

https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST-BMP280-DS001-18.pdf

1 piece I2C/SPI BMP280 3.3 Digital Barometric Pressure Altitude Sensor Module High Precision Atmospheric Module for Arduino

Arduino

The MCP3421 A/D converter and the Micro:bit

by shedboy71

The MCP3421 ADC can be used for various high accuracy analog-to-digital data conversion applications where ease of use, low power consumption and small footprint are major considerations.The MCP3421 is a single channel low-noise, high accuracy delta-sigma A/D converter with differential inputs and up to 18 bits of resolution in a small SOT-23-6 package.

The on-board precision 2.048V reference voltage enables a differential input range of ±2.048V. The device uses a two-wire I2C™ compatible interface and operates from a single power supply ranging from 2.7V to 5.5V. The MCP3421 ADC performs conversions at rates of 3.75, 15, 60 or 240 samples per second with corresponding resolutions of 18, 16, 14 and 12 bits. The onboard programmable gain amplifier (PGA) provides gain up to 8x. The device has two conversion modes: Continuous mode and One-Shot mode. In One-Shot mode, the device enters a low current standby mode automatically after a conversion, greatly reducing power use.

Features
    • 18-bit resolution
    • Small 6-lead SOT-23 packaging
    • Differential input operation
    • On-board voltage reference with 5 ppm/°C drift
    • On-board PGA, gains of 1, 2, 4, 8
    • Programmable data rate options
      • 3.75 SPS (18 bits)
      • 15 SPS (16 bits)
      • 60 SPS (14 bits)
      • 240 SPS (12 bits)
    • INL 10 ppm of FSR max
    • Low current consumption, 145 µA at 3V
    • One-shot or continuous conversion options
    • Supports I2C™ serial interface

Parts List

Part Link
MCP3421 MCP3421 I2C SOT23-6 delta-sigma ADC Evaluation Board
Connecting cable Free shipping Dupont line 120pcs 20cm male to male + male to female and female to female jumper wire Dupont cablefor Arduino
Micro:bit Micro:bit Development Board

 

Connection

Its an I2C device – I connected the VIN- to Gnd and Vin+ to Pin 6

 

Code

You need to download and install the following library – https://github.com/uChip/MCP342X

This is the default code example

[codesyntax lang=”cpp”]

// Include libraries this sketch will use
#include  <Wire.h>
#include  <MCP342X.h>

// Instantiate objects used in this project
MCP342X myADC;
int outputPin = 6;

void setup() 
{
  Wire.begin();  // join I2C bus
  TWBR = 12;  // 400 kHz (maximum)
  
  Serial.begin(9600); // Open serial connection to send info to the host
  while (!Serial) {}  // wait for Serial comms to become ready
  Serial.println("Starting up");
  Serial.println("Testing device connection...");
  Serial.println(myADC.testConnection() ? "MCP342X connection successful" : "MCP342X connection failed");
    
  myADC.configure( MCP342X_MODE_CONTINUOUS |
                   MCP342X_CHANNEL_1 |
                   MCP342X_SIZE_16BIT |
                   MCP342X_GAIN_1X
                 );

  Serial.println(myADC.getConfigRegShdw(), HEX);
  
}  // End of setup()

void loop() {
  static int16_t  result;
  for(int i=0; i<=255; i++)
  {
    myADC.startConversion();
    analogWrite(outputPin, i);
    myADC.getResult(&result);
    Serial.print(i);
    Serial.print("  ");
    Serial.print(result);
    Serial.print("  ");
    Serial.println(result, HEX);
  }
  
}  // End of loop()

[/codesyntax]

 

link

Datasheet – http://ww1.microchip.com/downloads/en/DeviceDoc/22003e.pdf

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