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Unlock new outdoor adventures using L76 and PIC18F46K20

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GNSS2 Click with EasyPIC v7

Published Jul 17, 2023

Click board™

GNSS2 Click

Development board

EasyPIC v7

Compiler

NECTO Studio

MCU

PIC18F46K20

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Hardware Overview

How does it work?

GNSS2 Click is based on the L76, a compact GNSS module from Quectel Wireless Solutions. The L76 supports the L1 band only (1575.42MHz) with tracking 33 channels, 99 acquisition channels, and 210 PRN channels. It can also acquire and track any mix of multiple satellite signals. The module is an ultra-low tracking power consumption device with a high sensitivity of -165dBm while tracking and -148dBm in acquisition mode with a less than 1-second reacquisition time. The greater number of visible satellites increases positioning accuracy (<2.5m CEP) and decreases acquisition time (<5s TTFF with a warm start). GNSS 2 Click supports anti-jamming and better positioning under weak signal conditions with onboard LNA, multi-tone active interference canceller, and balloon mode for high altitudes up to 80km. The L76 can automatically predict satellite orbits from data stored in its internal flash (EASY™ technology), and it can adaptively adjust its ON/OFF time to balance positioning accuracy and power

consumption (AlwaysLocate™ technology). To save power consumption, GNSS2 Click comes with a VBAT connector for connecting an external power supply which can supply power to the module’s SRAM memory. This memory serves for storing GPS information for quick Start-Up sequences. Periodic standby mode can control the power on/off time of GNSS2 Click periodically to reduce average power consumption, and on/off time can be configured using the PMTK command. GNSS2 Click will enter the periodic mode after successfully fixing the position. For communication with the host microcontroller, L76 uses the UART interface with commonly used UART RX and TX pins as its default communication protocol operating at 9600bps by default configuration to transmit and exchange data. In addition, the Click board™ features some other functions accessible through mikroBUS™ signals, such as Force on (FON), Reset (RST), and Standby (STB). Logic high state on FON will force the

module to be woken up from Backup mode, while the RST pin provides a general reset feature. The STB pin can put the module into or exit from Standby mode. In addition to precise positioning, the GNSS 2 Click also has an accurate timing signal indicated via a red LED indicator marked as PPS and an SMA antenna connector used to connect the appropriate active antenna that MIKROE has in its offer, for improved range and received signal strength. This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the PWR SEL jumper. An appropriate voltage level translator performs a proper logic voltage level conversion, while the onboard LDO, the AP7331, ensures the recommended voltage levels power module. However, the 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.

GNSS2 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

PIC18F46K20

Architecture

PIC

MCU Memory (KB)

64

Silicon Vendor

Microchip

Pin count

40

RAM (Bytes)

3936

You complete me!

Accessories

GNSS Active External Antenna is a unique multi-band type of antenna coming from u-Blox that is the perfect selection for high precision GNSS applications, which require highly accurate location abilities such as RTK. The ANN-MB-00 is a multi-band (L1, L2/E5b/B2I) active GNSS antenna with a 5m cable and SMA connector. The antenna supports GPS, GLONASS, Galileo, and BeiDou and includes a high-performance multi-band RHCP dual-feed patch antenna element, a built-in high-gain LNA with SAW pre-filtering, and a 5 m antenna cable with SMA connector, and is waterproof.

GNSS2 Click accessories image

Used MCU Pins

mikroBUS™ mapper

Wake Up
RA2
AN
Reset
RE1
RST
NC
NC
CS
NC
NC
SCK
NC
NC
MISO
NC
NC
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
Standby Mode
RC0
PWM
NC
NC
INT
UART TX
RC6
TX
UART RX
RC7
RX
NC
NC
SCL
NC
NC
SDA
Power Supply
5V
5V
Ground
GND
GND
1

Take a closer look

Schematic

GNSS2 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

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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 GNSS2 Click driver.

Key functions:

  • gnss2_generic_read - This function reads a desired number of data bytes by using UART serial interface

  • gnss2_clear_ring_buffers - This function clears UART tx and rx ring buffers

  • gnss2_parse_gpgga - This function parses the GPGGA data from the read response buffer

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 GNSS 2 Click Example.
 *
 * # Description
 * This example demonstrates the use of GNSS 2 click by reading and displaying
 * the GPS coordinates.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initializes the driver and logger.
 *
 * ## Application Task
 * Reads the received data, parses the GPGGA info from it, and once it receives the position fix
 * it will start displaying the coordinates on the USB UART.
 *
 * ## Additional Function
 * - static void gnss2_clear_app_buf ( void )
 * - static err_t gnss2_process ( gnss2_t *ctx )
 * - static void gnss2_parser_application ( char *rsp )
 * 
 * @author Stefan Filipovic
 *
 */

#include "board.h"
#include "log.h"
#include "gnss2.h"
#include "string.h"

#define PROCESS_BUFFER_SIZE 200

static gnss2_t gnss2;
static log_t logger;

static char app_buf[ PROCESS_BUFFER_SIZE ] = { 0 };
static int32_t app_buf_len = 0;

/**
 * @brief GNSS 2 clearing application buffer.
 * @details This function clears memory of application buffer and reset its length.
 * @return None.
 * @note None.
 */
static void gnss2_clear_app_buf ( void );

/**
 * @brief GNSS 2 data reading function.
 * @details This function reads data from device and concatenates data to application buffer.
 * @param[in] ctx : Click context object.
 * See #gnss2_t object definition for detailed explanation.
 * @return @li @c  0 - Read some data.
 *         @li @c -1 - Nothing is read.
 * See #err_t definition for detailed explanation.
 * @note None.
 */
static err_t gnss2_process ( gnss2_t *ctx );

/**
 * @brief GNSS 2 parser application function.
 * @details This function parses GNSS data and logs it on the USB UART. It clears app and ring buffers
 * after successfully parsing data.
 * @param[in] ctx : Click context object.
 * See #gnss2_t object definition for detailed explanation.
 * @param[in] rsp Response buffer.
 * @return None.
 * @note None.
 */
static void gnss2_parser_application ( gnss2_t *ctx, char *rsp );

void application_init ( void ) 
{
    log_cfg_t log_cfg;  /**< Logger config object. */
    gnss2_cfg_t gnss2_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.
    gnss2_cfg_setup( &gnss2_cfg );
    GNSS2_MAP_MIKROBUS( gnss2_cfg, MIKROBUS_1 );
    if ( UART_ERROR == gnss2_init( &gnss2, &gnss2_cfg ) ) 
    {
        log_error( &logger, " Communication init." );
        for ( ; ; );
    }
    log_info( &logger, " Application Task " );
}

void application_task ( void ) 
{
    if ( GNSS2_OK == gnss2_process( &gnss2 ) )
    {
        if ( PROCESS_BUFFER_SIZE == app_buf_len )
        {
            gnss2_parser_application( &gnss2, app_buf );
        }
    }
}

void main ( void ) 
{
    application_init( );

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

static void gnss2_clear_app_buf ( void ) 
{
    memset( app_buf, 0, app_buf_len );
    app_buf_len = 0;
}

static err_t gnss2_process ( gnss2_t *ctx ) 
{
    char rx_buf[ PROCESS_BUFFER_SIZE ] = { 0 };
    int32_t rx_size = 0;
    rx_size = gnss2_generic_read( ctx, rx_buf, PROCESS_BUFFER_SIZE );
    if ( rx_size > 0 ) 
    {
        int32_t buf_cnt = app_buf_len;
        if ( ( ( app_buf_len + rx_size ) > PROCESS_BUFFER_SIZE ) && ( app_buf_len > 0 ) ) 
        {
            buf_cnt = PROCESS_BUFFER_SIZE - ( ( app_buf_len + rx_size ) - PROCESS_BUFFER_SIZE );
            memmove ( app_buf, &app_buf[ PROCESS_BUFFER_SIZE - buf_cnt ], buf_cnt );
        }
        for ( int32_t rx_cnt = 0; rx_cnt < rx_size; rx_cnt++ ) 
        {
            if ( rx_buf[ rx_cnt ] ) 
            {
                app_buf[ buf_cnt++ ] = rx_buf[ rx_cnt ];
                if ( app_buf_len < PROCESS_BUFFER_SIZE )
                {
                    app_buf_len++;
                }
            }
        }
        return GNSS2_OK;
    }
    return GNSS2_ERROR;
}

static void gnss2_parser_application ( gnss2_t *ctx, char *rsp )
{
    char element_buf[ 100 ] = { 0 };
    if ( GNSS2_OK == gnss2_parse_gpgga( rsp, GNSS2_GPGGA_LATITUDE, element_buf ) )
    {
        static uint8_t wait_for_fix_cnt = 0;
        if ( strlen( element_buf ) > 0 )
        {
            log_printf( &logger, "\r\n Latitude: %.2s degrees, %s minutes \r\n", element_buf, &element_buf[ 2 ] );
            gnss2_parse_gpgga( rsp, GNSS2_GPGGA_LONGITUDE, element_buf );
            log_printf( &logger, " Longitude: %.3s degrees, %s minutes \r\n", element_buf, &element_buf[ 3 ] );
            memset( element_buf, 0, sizeof( element_buf ) );
            gnss2_parse_gpgga( rsp, GNSS2_GPGGA_ALTITUDE, element_buf );
            log_printf( &logger, " Altitude: %s m \r\n", element_buf );
            wait_for_fix_cnt = 0;
        }
        else
        {
            if ( wait_for_fix_cnt % 5 == 0 )
            {
                log_printf( &logger, " Waiting for the position fix...\r\n\n" );
                wait_for_fix_cnt = 0;
            }
            wait_for_fix_cnt++;
        }
        gnss2_clear_ring_buffers( ctx );
        gnss2_clear_app_buf( );
    }
}

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

Additional Support

Resources