Intermediate
30 min

Monitor pH in various samples for diagnostic insights with MCP607 and PIC18F57Q43

Decode the secrets of acidity and alkalinity

pH 2 Click with Curiosity Nano with PIC18F57Q43

Published Feb 13, 2024

Click board™

pH 2 Click

Dev. board

Curiosity Nano with PIC18F57Q43

Compiler

NECTO Studio

MCU

PIC18F57Q43

With a solution like this one designed to determine the acidity or alkalinity of a sample, measured using the pH electrode, you can embark on various applications and activities across different industries and fields

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Hardware Overview

How does it work?

pH 2 Click is based on the MCP607, a low-bias current operational amplifier from Microchip. This Click board™ operation is based on measuring hydrogen ion activity and produces an electrical potential or voltage. An electric potential develops when two liquids of different pH come into contact at opposite sides of a pH electrode thin glass membrane. The pH electrode represents a passive sensor, which means no excitation source (voltage or current) is required. It is classified as a bipolar sensor because its output can swing above and below the reference point. This board is a perfect solution for a wide variety of pH-sensing applications, including water treatment, chemical processing, medical instrumentation, and environmental test systems. pH 2 Click is used to detect the concentration of hydrogen ions in a solution and convert it into a corresponding

usable output signal. Because the pH electrode produces a bipolar signal, the electrode signal is first level shifted by the MCP607, a low bias current Op Amp set up in a unity-gain configuration with configurable reference for its calibration. Second, due to the high impedance of the electrode, another Op Amp inside the MCP607 provides the required high-input impedance buffer. A buffered signal can be then converted to a digital value using the MCP3221, a successive approximation A/D converter with a 12-bit resolution from Microchip using a 2-wire I2C compatible interface, or can be sent directly to an analog pin of the mikroBUS™ socket labeled as AN. The selection can be performed using an onboard SMD switch labeled OUT SEL, placing it in an appropriate position marked as AN or ADC. It is important to note that a pH electrode's sensitivity varies over

temperature. For this reason, it is possible to add the DS18B20, 1-wire thermometer via the DQ terminal to the pH 2 Click, whose temperature can be monitored via the DQ pin on the mikroBUS™ socket. In addition, the user can digitally monitor different statuses in operation through the ST1 and ST2 pins on the mikroBUS™ socket or through visual detection on the STAT1 and STAT2 LEDs. 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.

pH 2 Click hardware overview image

Features overview

Development board

PIC18F57Q43 Curiosity Nano evaluation kit is a cutting-edge hardware platform designed to evaluate microcontrollers within the PIC18-Q43 family. Central to its design is the inclusion of the powerful PIC18F57Q43 microcontroller (MCU), offering advanced functionalities and robust performance. Key features of this evaluation kit include a yellow user LED and a responsive

mechanical user switch, providing seamless interaction and testing. The provision for a 32.768kHz crystal footprint ensures precision timing capabilities. With an onboard debugger boasting a green power and status LED, programming and debugging become intuitive and efficient. Further enhancing its utility is the Virtual serial port (CDC) and a debug GPIO channel (DGI

GPIO), offering extensive connectivity options. Powered via USB, this kit boasts an adjustable target voltage feature facilitated by the MIC5353 LDO regulator, ensuring stable operation with an output voltage ranging from 1.8V to 5.1V, with a maximum output current of 500mA, subject to ambient temperature and voltage constraints.

PIC18F57Q43 Curiosity Nano double side image

Microcontroller Overview

MCU Card / MCU

default

Architecture

PIC

MCU Memory (KB)

128

Silicon Vendor

Microchip

Pin count

48

RAM (Bytes)

8196

You complete me!

Accessories

Curiosity Nano Base for Click boards is a versatile hardware extension platform created to streamline the integration between Curiosity Nano kits and extension boards, tailored explicitly for the mikroBUS™-standardized Click boards and Xplained Pro extension boards. This innovative base board (shield) offers seamless connectivity and expansion possibilities, simplifying experimentation and development. Key features include USB power compatibility from the Curiosity Nano kit, alongside an alternative external power input option for enhanced flexibility. The onboard Li-Ion/LiPo charger and management circuit ensure smooth operation for battery-powered applications, simplifying usage and management. Moreover, the base incorporates a fixed 3.3V PSU dedicated to target and mikroBUS™ power rails, alongside a fixed 5.0V boost converter catering to 5V power rails of mikroBUS™ sockets, providing stable power delivery for various connected devices.

Curiosity Nano Base for Click boards accessories 1 image

This probe can be used with all pH meters with an input for the BNC connection with a 1m cable. The sensitive part of the probe (in the shape of a ball) is partially protected by a probe's plastic body, which reduces the possibility of mechanical damage. The EPH101 is used to measure the pH value of various liquids (due to the present plastic protection), and it can also be immersed in liquids inflowed in a system). It is stored in a plastic gel bottle with a very long shelf life. A pH (potential of Hydrogen) probe measures the hydrogen ion activity in a liquid. A membrane at the tip of a pH probe permits hydrogen ions from the liquid to be measured to defuse into the outer layer of the membrane while larger ions remain in the solution. The difference in the concentration of hydrogen ions outside the probe vs. inside the pH probe creates a small current proportional to the concentration of hydrogen ions in the measured liquid.

pH 2 Click accessories image

Used MCU Pins

mikroBUS™ mapper

Analog Output
PA0
AN
Status Signal 1
PA7
RST
NC
NC
CS
NC
NC
SCK
NC
NC
MISO
NC
NC
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
Thermometer Data
PB0
PWM
Status Signal 2
PA6
INT
NC
NC
TX
NC
NC
RX
I2C Clock
PB2
SCL
I2C Data
PB1
SDA
Power Supply
5V
5V
Ground
GND
GND
1

Take a closer look

Click board™ Schematic

pH 2 Click Schematic schematic

Step by step

Project assembly

Curiosity Nano Base for Click boards front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Curiosity Nano with PIC18F57Q43 as your development board.

Curiosity Nano Base for Click boards front image hardware assembly
Charger 27 Click front image hardware assembly
PIC18F47Q10 Curiosity Nano front image hardware assembly
Prog-cut hardware assembly
Charger 27 Click complete accessories setup image hardware assembly
Curiosity Nano with PICXXX Access MB 1 - upright/background hardware assembly
Necto image step 2 hardware assembly
Necto image step 3 hardware assembly
Necto image step 4 hardware assembly
Necto image step 5 hardware assembly
Necto image step 6 hardware assembly
PIC18F57Q43 Curiosity MCU Step hardware assembly
Necto No Display image step 8 hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Debug Image Necto Step hardware assembly

Track your results in real time

Application Output

1. Application Output - In Debug mode, the 'Application Output' window enables real-time data monitoring, offering direct insight into execution results. Ensure proper data display by configuring the environment correctly using the provided tutorial.

2. UART Terminal - Use the UART Terminal to monitor data transmission via a USB to UART converter, allowing direct communication between the Click board™ and your development system. Configure the baud rate and other serial settings according to your project's requirements to ensure proper functionality. For step-by-step setup instructions, refer to the provided tutorial.

3. Plot Output - The Plot feature offers a powerful way to visualize real-time sensor data, enabling trend analysis, debugging, and comparison of multiple data points. To set it up correctly, follow the provided tutorial, which includes a step-by-step example of using the Plot feature to display Click board™ readings. To use the Plot feature in your code, use the function: plot(*insert_graph_name*, variable_name);. This is a general format, and it is up to the user to replace 'insert_graph_name' with the actual graph name and 'variable_name' with the parameter to be displayed.

Software Support

Library Description

This library contains API for pH 2 Click driver.

Key functions:

  • ph2_calibrate - Ph 2 calibrate function

  • ph2_calculate_ph - Ph 2 calculate pH value function

  • ph2_calibrate_offset - Ph 2 calibrate offset function

Open Source

Code example

The complete application code and a ready-to-use project are available through the NECTO Studio Package Manager for direct installation in the NECTO Studio. The application code can also be found on the MIKROE GitHub account.

/*!
 * @file main.c
 * @brief pH 2 Click Example.
 *
 * # Description
 * This library contains API for pH 2 Click driver. 
 * The library initializes and defines the I2C bus drivers or 
 * ADC drivers to read data from pH probe.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initializes the driver and performs offset calibration, 
 * as well as calibration in pH-neutral substance.

 *
 * ## Application Task
 * This example demonstrates the use of the pH 2 Click board by 
 * reading pH value of the substance where probe is placed.
 *
 * @author Stefan Ilic
 *
 */

#include "board.h"
#include "log.h"
#include "ph2.h"

static ph2_t ph2;   /**< pH 2 Click driver object. */
static log_t logger;    /**< Logger object. */

void application_init ( void )
{
    log_cfg_t log_cfg;  /**< Logger config object. */
    ph2_cfg_t ph2_cfg;  /**< Click config object. */

    /** 
     * 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.
    ph2_cfg_setup( &ph2_cfg );
    PH2_MAP_MIKROBUS( ph2_cfg, MIKROBUS_1 );
    err_t init_flag = ph2_init( &ph2, &ph2_cfg );
    if ( ( ADC_ERROR == init_flag ) || ( I2C_MASTER_ERROR == init_flag ) )
    {
        log_error( &logger, " Communication init." );
        for ( ; ; );
    }

    log_printf( &logger, " ================================ \r\n" );
    log_printf( &logger, "     Performing calibration       \r\n" );
    log_printf( &logger, " ================================ \r\n" );
    log_printf( &logger, " Disconect BNC connector, \r\n" );
    log_printf( &logger, "    short-circuit it, \r\n" );
    log_printf( &logger, " adjust offset potentiometer \r\n" );
    log_printf( &logger, " ================================ \r\n" );
    log_printf( &logger, " STAT1 - turn clockwise \r\n" );
    log_printf( &logger, " STAT2 - turn counter-clockwise \r\n" );
    log_printf( &logger, " ================================ \r\n" );
    
    ph2_calibrate_offset( &ph2 );
    
    log_printf( &logger, " Calibration completed \r\n" );
    log_printf( &logger, " ================================ \r\n" );
    
    log_printf( &logger, " Connect probe back \r\n" );
    log_printf( &logger, " ================================ \r\n" );
    Delay_ms( 5000 );
    log_printf( &logger, "  Place probe into pH  \r\n" );
    log_printf( &logger, " neutral substance for \r\n" );
    log_printf( &logger, " mid point calibration \r\n" );
    log_printf( &logger, " ================================ \r\n" );
    Delay_ms( 5000 );
    log_printf( &logger, " Starting calibration  \r\n" );
    log_printf( &logger, " ================================ \r\n" );  
    
    ph2_calibrate( &ph2, 7 );
    
    log_printf( &logger, " Calibration done!  \r\n" );
    log_printf( &logger, " ================================ \r\n" ); 
    
    log_info( &logger, " Application Task " );
    log_printf( &logger, " ================================ \r\n" ); 
}

void application_task ( void ) 
{
    float pH_val = 0;
    ph2_calculate_ph( &ph2, &pH_val );
    log_printf( &logger, " pH value: %.3f \r\n", pH_val );
    log_printf( &logger, " ================================ \r\n" ); 
    Delay_ms( 1000 );
}

void main ( void ) 
{
    application_init( );

    for ( ; ; ) 
    {
        application_task( );
    }
}

// ------------------------------------------------------------------------ END

Additional Support

Resources

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