Breathe easy with accurate NO2 detection using 3SP-NO2-20 and STM32F030R8
Say NO to NO2 pollution
Published Feb 26, 2024
Click board™
NO2 Click
Dev Board
Nucleo-64 with STM32F030R8 MCU
Compiler
NECTO Studio
MCU
STM32F030R8
Our NO2 monitoring solution offers real-time data to individuals, cities, and industries, enabling them to combat nitrogen dioxide pollution for improved air quality
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Hardware Overview
How does it work?
NO2 Click is based on the 3SP-NO2-20 gas sensor from SPEC Sensors, which can sense NO2 concentration up to 20ppm. The sensor has a very short response time; however, the longer it is exposed to a particular gas, the more accurate data it can provide. This is especially true when calibration is performed. The sensor is sensitive to small dust particles, condensed water, and other impurities, which might prevent gas from reaching the sensor. It is advised to protect the sensor when used in critical applications. In ideal conditions, the lifetime of this sensor is indefinite, but in real-life applications, the expected operating life is more than five years (10 years at 23 ± 3 ˚C; 40 ± 10 %RH). Although very reliable and accurate, this sensor is great for building relative gas sensing applications. For example, it can detect an increased level of NO2 gas. However, when developing applications for the absolute gas concentration, the sensor must be calibrated, and the measurement data needs to be compensated. Factors such as humidity and temperature can affect measurements; the sensor reaction curve to a specific measured gas (nitrogen dioxide) is not completely linear, and other gases might affect the measurement (cross-sensitivity to other gases). For this reason, a range of calibration routines must be done in the working environment conditions to calculate the
absolute gas concentration. NO2 click uses the LMP91000, a configurable AFE potentiostat IC for low-power chemical sensing applications, from Texas Instruments. It provides the complete sensor solution, generating the output voltage proportional to the sensor current. A trans-impedance amplifier (TIA) with a programmable gain is used to convert the current through the sensor, covering the range from 5μA to 750 μA, depending on the used sensor. The voltage between the referent electrode (RE) and the working electrode (WE) is held constant, with the bias set by the variable bias circuitry. This type of sensor performs best when a fixed bias voltage is applied. The sensor manufacturer recommends a 200mV fixed bias for the sensor on this Click board™. The bias voltage and the TIA gain can be set via the I2C registers. In addition, an embedded thermal sensor in the AFE IC can be used for the result compensation if needed. It is available via the VOUT pin as the analog voltage value concerning GND. The Click board™ has two additional ICs onboard. The first is the MCP3221, a 12-bit successive approximation register A/D converter from Microchip. The second IC is the OPA344, a single-supply, rail-to-rail operational amplifier from Texas Instruments. It is possible to use the onboard switch, labeled as AN SEL, to select the IC to which the VOUT pin from the
LMP91000 AFE is routed. If the switch is in the ADC position, the VOUT pin will be routed to the input of the MCP3221 ADC. This allows the voltage value at the VOUT pin to be read via the I2C interface as digital information. When the switch is in the AN position, it will route the VOUT pin of the LMP91000 AFE IC to the input of the OPA344. The output of the OPA344 op-amp has a stable unity gain, acting as a buffer so that the voltage at the VOUT pin of the AFE can be sampled by the host MCU via the AN pin of the mikroBUS™. The RST pin on the mikroBUS™ is routed to the MEMB pin of the LMP91000, and it is used to enable the I2C interface section, thus making it possible to use more than one chip on the same I2C bus. When driven to a LOW logic level, the I2C communication is enabled, and the host device (host MCU) can issue a START condition. The RST pin should stay at LOW during the communication. This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the VCC SEL jumper. This way, both 3.3V and 5V capable MCUs can use the communication lines properly. Also, this Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used as a reference for further development.
Features overview
Development board
Nucleo-64 with STM32F030R8 MCU offers a cost-effective and adaptable platform for developers to explore new ideas and prototype their designs. This board harnesses the versatility of the STM32 microcontroller, enabling users to select the optimal balance of performance and power consumption for their projects. It accommodates the STM32 microcontroller in the LQFP64 package and includes essential components such as a user LED, which doubles as an ARDUINO® signal, alongside user and reset push-buttons, and a 32.768kHz crystal oscillator for precise timing operations. Designed with expansion and flexibility in mind, the Nucleo-64 board features an ARDUINO® Uno V3 expansion connector and ST morpho extension pin
headers, granting complete access to the STM32's I/Os for comprehensive project integration. Power supply options are adaptable, supporting ST-LINK USB VBUS or external power sources, ensuring adaptability in various development environments. The board also has an on-board ST-LINK debugger/programmer with USB re-enumeration capability, simplifying the programming and debugging process. Moreover, the board is designed to simplify advanced development with its external SMPS for efficient Vcore logic supply, support for USB Device full speed or USB SNK/UFP full speed, and built-in cryptographic features, enhancing both the power efficiency and security of projects. Additional connectivity is
provided through dedicated connectors for external SMPS experimentation, a USB connector for the ST-LINK, and a MIPI® debug connector, expanding the possibilities for hardware interfacing and experimentation. Developers will find extensive support through comprehensive free software libraries and examples, courtesy of the STM32Cube MCU Package. This, combined with compatibility with a wide array of Integrated Development Environments (IDEs), including IAR Embedded Workbench®, MDK-ARM, and STM32CubeIDE, ensures a smooth and efficient development experience, allowing users to fully leverage the capabilities of the Nucleo-64 board in their projects.
Microcontroller Overview
MCU Card / MCU
Architecture
ARM Cortex-M0
MCU Memory (KB)
64
Silicon Vendor
STMicroelectronics
Pin count
64
RAM (Bytes)
8192
You complete me!
Accessories
Click Shield for Nucleo-64 comes equipped with two proprietary mikroBUS™ sockets, allowing all the Click board™ devices to be interfaced with the STM32 Nucleo-64 board with no effort. This way, Mikroe allows its users to add any functionality from our ever-growing range of Click boards™, such as WiFi, GSM, GPS, Bluetooth, ZigBee, environmental sensors, LEDs, speech recognition, motor control, movement sensors, and many more. More than 1537 Click boards™, which can be stacked and integrated, are at your disposal. The STM32 Nucleo-64 boards are based on the microcontrollers in 64-pin packages, a 32-bit MCU with an ARM Cortex M4 processor operating at 84MHz, 512Kb Flash, and 96KB SRAM, divided into two regions where the top section represents the ST-Link/V2 debugger and programmer while the bottom section of the board is an actual development board. These boards are controlled and powered conveniently through a USB connection to program and efficiently debug the Nucleo-64 board out of the box, with an additional USB cable connected to the USB mini port on the board. Most of the STM32 microcontroller pins are brought to the IO pins on the left and right edge of the board, which are then connected to two existing mikroBUS™ sockets. This Click Shield also has several switches that perform functions such as selecting the logic levels of analog signals on mikroBUS™ sockets and selecting logic voltage levels of the mikroBUS™ sockets themselves. Besides, the user is offered the possibility of using any Click board™ with the help of existing bidirectional level-shifting voltage translators, regardless of whether the Click board™ operates at a 3.3V or 5V logic voltage level. Once you connect the STM32 Nucleo-64 board with our Click Shield for Nucleo-64, you can access hundreds of Click boards™, working with 3.3V or 5V logic voltage levels.
Used MCU Pins
mikroBUS™ mapper
Take a closer look
Schematic
Step by step
Project assembly
Start by selecting your development board and Click board™. Begin with the Nucleo-64 with STM32F030R8 MCU as your development board.
Track your results in real time
Application Output via Debug Mode
1. Once the code example is loaded, pressing the "DEBUG" button initiates the build process, programs it on the created setup, and enters Debug mode.
2. After the programming is completed, a header with buttons for various actions within the IDE becomes visible. Clicking the green "PLAY" button starts reading the results achieved with the Click board™. The achieved results are displayed in the Application Output tab.
Software Support
Library Description
This library contains API for NO2 Click driver.
Key functions:
no2_enable- Device Enable functionno2_read_adc- Function for read ADC sensor datano2_get_no_2_ppm- Get NO2 Data function
Open Source
Code example
This example can be found in NECTO Studio. Feel free to download the code, or you can copy the code below.
/*!
* \file
* \brief No2 Click example
*
* # Description
* This application measures NO2.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initializes I2C driver and device configuration.
*
* ## Application Task
* Gets NO2 (Nitrogen dioxide) data as ppm value and logs to USBUART every 500ms.
*
* \author MikroE Team
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "no2.h"
// ------------------------------------------------------------------ VARIABLES
static no2_t no2;
static log_t logger;
// ------------------------------------------------------ APPLICATION FUNCTIONS
void application_init ( void )
{
log_cfg_t log_cfg;
no2_cfg_t cfg;
/**
* Logger initialization.
* Default baud rate: 115200
* Default log level: LOG_LEVEL_DEBUG
* @note If USB_UART_RX and USB_UART_TX
* are defined as HAL_PIN_NC, you will
* need to define them manually for log to work.
* See @b LOG_MAP_USB_UART macro definition for detailed explanation.
*/
LOG_MAP_USB_UART( log_cfg );
log_init( &logger, &log_cfg );
log_info( &logger, "---- Application Init ----" );
// Click initialization.
no2_cfg_setup( &cfg );
NO2_MAP_MIKROBUS( cfg, MIKROBUS_1 );
no2_init( &no2, &cfg );
no2_default_cfg( &no2 );
log_printf( &logger, "NO2 is initialized \r\n" );
Delay_ms( 300 );
}
void application_task ( void )
{
float no2_value;
no2_value = no2_get_no_2_ppm( &no2 );
log_printf( &logger, "NO2 value : %.2f ppm \r\n", no2_value );
Delay_ms( 500 );
}
void main ( void )
{
application_init( );
for ( ; ; )
{
application_task( );
}
}
// ------------------------------------------------------------------------ END
