Intermediate
20 min
0

Experience pH measurement at its finest with pH EZO and PIC18F4550

Your go-to expert for precise pH readings, every time

pH Click with EasyPIC v7

Published Nov 09, 2023

Click board™

pH Click

Development board

EasyPIC v7

Compiler

NECTO Studio

MCU

PIC18F4550

Count on our pH meter for reliable pH monitoring in any environment or application.

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Hardware Overview

How does it work?

pH Click is based on the pH EZO™, a 6th-generation embedded pH circuit that offers the highest level of stability and accuracy from AtlasScientific. With an easy-to-use UART data protocol (with additional I2C serial interface), simple command structure, and flexible calibration protocol that supports single-point, two-point, or three-point calibration, this Click board™ works well with any off-the-shelf pH probe. It has temperature-dependent or independent readings with a full range of pH readings from 0.001 to 14.000. The pH EZO™ circuit is characterized by great sensitivity that gives its accuracy. When electrical noise interferes with the pH readings, it is common to see rapidly fluctuating readings or readings that are consistently off. To verify that electrical noise is causing inaccurate readings, place the pH probe in a cup of water by itself. The pH readings should

stabilize quickly, confirming that electrical noise was the issue. This Click board™ uses the UART communication interface as its default communication protocol that supports all standard baud rates up to 115.200 but also provides the possibility of using the I2C serial interface. The selection can be performed by positioning SMD jumpers labeled COMM SEL to an appropriate position. Note that all jumpers must be placed on the same side, or the Click board™ may become unresponsive. This Click Board™ uses the UART communication interface as its default communication protocol that supports all standard baud rates up to 115.200 but also provides the possibility of using the I2C serial interface. The selection can be performed by positioning SMD jumpers labeled COMM SEL to an appropriate position. Note that all jumpers must be placed on the same side, or the Click board™ may become

unresponsive. Also, the pH EZO™ circuit contains an LED indicator that informs the user about the current state of the pH circuit at any time with a specified color. The green color indicates Standby Mode, the yellow color indicates sent pH data, and the blue indicates pH data being read. Besides, there is a purple color that signals a change in the Baud rate, a red color that represents an invalid command given by the user, and a white color that the LED flashes when a device is connected to the circuit. 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 Click hardware overview image

Features overview

Development board

EasyPIC v7 is the seventh generation of PIC development boards specially designed to develop embedded applications rapidly. It supports a wide range of 8-bit PIC microcontrollers from Microchip and has a broad set of unique functions, such as a powerful onboard mikroProg programmer and In-Circuit debugger over USB-B. The development board is well organized and designed so that the end-user has all the necessary elements in one place, such as switches, buttons, indicators, connectors, and others. With four different connectors for each port, EasyPIC v7 allows you to connect accessory boards, sensors, and custom electronics more efficiently than ever. Each part of

the EasyPIC v7 development board contains the components necessary for the most efficient operation of the same board. An integrated mikroProg, a fast USB 2.0 programmer with mikroICD hardware In-Circuit Debugger, offers many valuable programming/debugging options and seamless integration with the Mikroe software environment. Besides it also includes a clean and regulated power supply block for the development board. It can use various external power sources, including an external 12V power supply, 7-23V AC or 9-32V DC via DC connector/screw terminals, and a power source via the USB Type-B (USB-B) connector. Communication options such as

USB-UART and RS-232 are also included, alongside the well-established mikroBUS™ standard, three display options (7-segment, graphical, and character-based LCD), and several different DIP sockets. These sockets cover a wide range of 8-bit PIC MCUs, from PIC10F, PIC12F, PIC16F, PIC16Enh, PIC18F, PIC18FJ, and PIC18FK families. EasyPIC v7 is an integral part of the Mikroe ecosystem for rapid development. Natively supported by Mikroe software tools, it covers many aspects of prototyping and development thanks to a considerable number of different Click boards™ (over a thousand boards), the number of which is growing every day.

EasyPIC v7 horizontal image

Microcontroller Overview

MCU Card / MCU

PIC18F4550

Architecture

PIC

MCU Memory (KB)

32

Silicon Vendor

Microchip

Pin count

40

RAM (Bytes)

2048

You complete me!

Accessories

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 Click accessories image

Used MCU Pins

mikroBUS™ mapper

NC
NC
AN
NC
NC
RST
NC
NC
CS
NC
NC
SCK
NC
NC
MISO
NC
NC
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
NC
NC
PWM
NC
NC
INT
UART TX
RC6
TX
UART RX
RC7
RX
I2C Clock
RC3
SCL
I2C Data
RC4
SDA
Power Supply
5V
5V
Ground
GND
GND
1

Take a closer look

Schematic

pH Click Schematic schematic

Step by step

Project assembly

EasyPIC v7 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the EasyPIC v7 as your development board.

EasyPIC v7 front image hardware assembly
GNSS2 Click front image hardware assembly
MCU DIP 40 hardware assembly
GNSS2 Click complete accessories setup image hardware assembly
EasyPIC v7 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 Compiler Selection Step Image hardware assembly
NECTO Output Selection Step Image hardware assembly
Necto image step 6 hardware assembly
Necto DIP image step 7 hardware assembly
EasyPIC PRO v7a Display Selection Necto Step hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Necto PreFlash Image hardware assembly

Track your results in real time

Application Output

After pressing the "FLASH" button on the left-side panel, it is necessary to open the UART terminal to display the achieved results. By clicking on the Tools icon in the right-hand panel, multiple different functions are displayed, among which is the UART Terminal. Click on the offered "UART Terminal" icon.

UART Application Output Step 1

Once the UART terminal is opened, the window takes on a new form. At the top of the tab are two buttons, one for adjusting the parameters of the UART terminal and the other for connecting the UART terminal. The tab's lower part is reserved for displaying the achieved results. Before connecting, the terminal has a Disconnected status, indicating that the terminal is not yet active. Before connecting, it is necessary to check the set parameters of the UART terminal. Click on the "OPTIONS" button.

UART Application Output Step 2

In the newly opened UART Terminal Options field, we check if the terminal settings are correct, such as the set port and the Baud rate of UART communication. If the data is not displayed properly, it is possible that the Baud rate value is not set correctly and needs to be adjusted to 115200. If all the parameters are set correctly, click on "CONFIGURE".

UART Application Output Step 3

The next step is to click on the "CONNECT" button, after which the terminal status changes from Disconnected to Connected in green, and the data is displayed in the Received data field.

UART Application Output Step 4

Software Support

Library Description

This library contains API for pH Click driver.

Key functions:

  • ph_send_cmd - Send command function.

  • ph_get_cmd_resp - Send get response function.

  • ph_switch_led - Toggle LED 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 main.c
 * @brief pH Click Example.
 *
 * # Description
 * This example reads and processes data from pH clicks.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initializes UART driver, performing a factory reset of the device, disabling continuous read,
 * and performing calibration at the midpoint on the pH scale.
 *
 * ## Application Task
 * This example shows the capabilities of the pH Click board by performing a reading of the 
 * pH value of the substance in which the probe is submerged and displaying readings via the 
 * USART terminal.
 *
 * @author Stefan Ilic
 *
 */

#include "board.h"
#include "log.h"
#include "ph.h"

#define PROCESS_BUFFER_SIZE 200

static ph_t ph;
static log_t logger;

static char app_buf[ PROCESS_BUFFER_SIZE ] = { 0 };

void application_init ( void ) 
{
    log_cfg_t log_cfg;  /**< Logger config object. */
    ph_cfg_t ph_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.
    ph_cfg_setup( &ph_cfg );
    PH_MAP_MIKROBUS( ph_cfg, MIKROBUS_1 );
    if ( UART_ERROR == ph_init( &ph, &ph_cfg ) ) 
    {
        log_error( &logger, " Communication init." );
        for ( ; ; );
    }
    
    ph_factory_rst( &ph, app_buf );
    Delay_ms( 1000 );
    
    ph_cont_read( &ph, 0, app_buf );
    log_printf( &logger, "-----------------------\r\n" );
    log_printf( &logger, "   -- Initialized --   \r\n" );
    log_printf( &logger, "-----------------------\r\n" );
    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" );
    for ( uint8_t n_cnt = 0; n_cnt < 20; n_cnt++ )
    {
        Delay_ms( 1000 );
    }
    log_printf( &logger, " Starting calibration  \r\n" );
    log_printf( &logger, "-----------------------\r\n" );
    ph_perf_calib ( &ph, PH_CMD_CALIB_MID, 7.000, app_buf );
    Delay_ms( 1000 );
    log_printf( &logger, " Calibration done!     \r\n" );
    log_printf( &logger, "-----------------------\r\n" );
    
    log_printf( &logger, " - Application  task -\r\n" );
    log_printf( &logger, "-----------------------\r\n" );
    ph_send_cmd( &ph, PH_CMD_DIS_RSP_CODES );
    Delay_ms( 1000 );
    ph_clr_log_buf( app_buf );
}

void application_task ( void ) 
{
    ph_send_cmd ( &ph, PH_CMD_SET_SNGL_READ );
    ph_response( &ph, app_buf );
    log_printf( &logger, " pH value: %s ", app_buf );
    log_printf( &logger, "-----------------------\r\n" );
    ph_clr_log_buf( app_buf );
    Delay_ms( 1000 );
}

void main ( void ) 
{
    application_init( );

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

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

Additional Support

Resources