Build RTK Base station with LG69TASMD and STM32F767BI
Improve positional accuracy
Published Mar 06, 2023
Click board™
RTK Base Click
Dev Board
Clicker 4 for STM32
Compiler
NECTO Studio
MCU
STM32F767BI
Increase the accuracy of GNSS positions using a fixed base station
A
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Hardware Overview
How does it work?
RTK Base Click is based on the LG69TASMD, a multi-constellation GNSS module featuring a high-performance and high-reliability positioning engine from Quectel Wireless Solutions that improve the positional accuracy of the compatible RTK Rover board. The LG69TASMD has a dual-band supporting up to four concurrent global constellations. It features STMicroelectronics®' fifth-generation positioning receiver platform with 80 tracking, 4 fast acquisition channels, and Quectel's high-performance YG0063AA geodetic antenna. Designed according to the IATF 16949:2016 standard, the LG69TASMD has GPS+BDS+Galileo+QZSS as a default GNSS constellation and an integrated LNA for improved sensitivity. It can receive and track GPS L1 C/A and L5 and Galileo E1 and E5a signals centered at 1575.42MHz and 1176.45MHz, and BeiDou B1I and B2a signals centered at 1561.098MHz and 1176.45MHz. The ability to receive and track BeiDou signals with GPS results in higher coverage, improved reliability, and better accuracy. RTK Base Click communicates with an MCU using the UART interface, with commonly-used
RX and TX pins alongside one data-ready pin (INT), which informs the host MCU to receive data when the buffer transmission is full. It is also equipped with a USB type C connector, which allows the module to be powered and configured by a personal computer (PC) using FT2232D, a compact USB to a serial UART interface device designed to operate efficiently with USB host controllers. The LG69TASMD module provides RTK data output as a base station, supporting static mode alongside fixed mode, set using corresponding commands. It can use its previously-measured antenna positioning coordinates. If this coordinate has the best effect, this method can ensure that the Rover achieves the best accuracy. The LG69TASMD can also self-survey its coordinates in situations without using other methods to measure the base station antenna. The user provides accuracy constraints and the shortest observation time in this mode. In addition to the interface pins, this board uses additional mikroBUS™ pins. A reset signal with the onboard RESET button, routed on the RST pin of the mikroBUS™ socket, performs a reset function of the module, while the
SHD pin routed on the AN pin of the mikroBUS™enables the power supply to the LG69TASMD to be switched ON/OFF. The module can use Boot Download Mode for firmware update via the BT pin routed on the RST pin of the mikroBUS™ socket, alongside a blue LED indicator marked as PPS for time pulse signal information and indication. The module enters Normal operating mode by keeping the BT pin on a low logic state during the Startup sequence. Otherwise, the module enters Boot Download Mode when the pin is high during Startup. A specific addition to this Click board™ is several testpoints that enable additional module features. This Click board™ can operate with both 3.3V and 5V MCUs. As its main power supply, the LG69TASMD uses 3.3V obtained from the MCP1826 LDO; additional backup power can be provided using a coin-shaped battery. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. However, the Click board™ comes equipped with a library containing functions and example code that can be used as a reference for further development.
Features overview
Development board
Clicker 4 for STM32 is a compact development board designed as a complete solution that brings the flexibility of add-on Click boards™ to your favorite microcontroller, making it a perfect starter kit for implementing your ideas. It comes with an onboard 32-bit ARM Cortex-M4 microcontroller, the STM32F767BI from STMicroelectronics, four mikroBUS™ sockets for Click board™ connectivity, a USB connector, LED indicators, buttons, a debugger/programmer connector, two 23-pin headers for interfacing with external electronics, and more. Thanks to innovative manufacturing technology, it allows you to build gadgets with
unique functionalities and features quickly. Each part of the Clicker 4 for STM32 development kit contains the components necessary for the most efficient operation of the same board. In addition to the possibility of choosing the Clicker 4 for STM32 programming method, using an external CODEGRIP or mikroProg programmer connected to the onboard JTAG/SWD header, the Clicker 4 board also includes a clean and regulated power supply block. It provides several ways of board-powering; through the USB Type-C (USB-C) connector using a power supply delivered by the USB HOST (i.e., personal computer), USB wall
adapter, or a Li-Po/Li-Ion battery via an onboard battery connector. All communication methods that mikroBUS™ itself supports are on this board (plus USB-DEVICE), including the well-established mikroBUS™ socket, several user-configurable buttons, and LED indicators. Clicker 4 for STM32 is an integral part of the Mikroe ecosystem, allowing you to create a new application in minutes. Natively supported by Mikroe software tools, it covers many aspects of prototyping thanks to a considerable number of different Click boards™ (over a thousand boards), the number of which is growing every day.
Microcontroller Overview
MCU Card / MCU
Architecture
ARM Cortex-M7
MCU Memory (KB)
2048
Silicon Vendor
STMicroelectronics
Pin count
208
RAM (Bytes)
524288
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 Clicker 4 for STM32 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 RTK Base Click driver.
Key functions:
rtkbase_generic_readThis function reads a desired number of data bytes by using UART serial interface.rtkbase_rx_bytes_availableThis function returns the number of bytes available in the RX ring buffer.rtkbase_calculate_crc24This function calculates and returns the CRC 24-bit of RTCM3 packet input. The CRC across the whole packet should sum to zero (remainder).
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 RTK Base Click Example.
*
* # Description
* This example demonstrates the use of RTK Base click by reading and displaying the RTCM3 messages.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initializes the driver and logger.
*
* ## Application Task
* Reads and parses the RTCM3 messages received from the module, and displays them on the USB UART.
*
* ## Additional Function
* - static void rtkbase_clear_app_buf ( void )
* - static err_t rtkbase_process_rtcm3 ( rtkbase_t *ctx )
*
* @note
* The click board comes with the default baud rate of 460800, but the baud rate is set to 115200
* in the example due to code portability and speed limitations of some MCUs. So in order to run
* the example you will need to adjust the baud rate using Quectel QGNSS evaluation software.
*
* @author Stefan Filipovic
*
*/
#include "board.h"
#include "log.h"
#include "rtkbase.h"
#define PROCESS_BUFFER_SIZE 300
static rtkbase_t rtkbase;
static log_t logger;
static char app_buf[ PROCESS_BUFFER_SIZE ] = { 0 };
static uint16_t app_buf_len = 0;
/**
* @brief RTK Base clearing application buffer.
* @details This function clears memory of application buffer and reset its length.
* @return None.
* @note None.
*/
static void rtkbase_clear_app_buf ( void );
/**
* @brief RTK Base process rtcm3 function.
* @details This function reads and processes the RTCM3 messages and displays them on the USB UART.
* @param[in] ctx : Click context object.
* See #rtkbase_t object definition for detailed explanation.
* @return @li @c 0 - Successfully read RTCM3 message.
* @li @c -1 - Read error.
* See #err_t definition for detailed explanation.
* @note None.
*/
static err_t rtkbase_process_rtcm3 ( rtkbase_t *ctx );
void application_init ( void )
{
log_cfg_t log_cfg; /**< Logger config object. */
rtkbase_cfg_t rtkbase_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.
rtkbase_cfg_setup( &rtkbase_cfg );
RTKBASE_MAP_MIKROBUS( rtkbase_cfg, MIKROBUS_1 );
if ( UART_ERROR == rtkbase_init( &rtkbase, &rtkbase_cfg ) )
{
log_error( &logger, " Communication init." );
for ( ; ; );
}
log_info( &logger, " Application Task " );
}
void application_task ( void )
{
rtkbase_process_rtcm3 ( &rtkbase );
rtkbase_clear_app_buf( );
}
void main ( void )
{
application_init( );
for ( ; ; )
{
application_task( );
}
}
static void rtkbase_clear_app_buf ( void )
{
memset( app_buf, 0, app_buf_len );
app_buf_len = 0;
}
static err_t rtkbase_process_rtcm3 ( rtkbase_t *ctx )
{
#define RTKBASE_HEADER_0 0xD3
#define RTKBASE_HEADER_1 0x00
for ( ; ; ) // loop until a header byte 0 is read
{
while ( rtkbase_rx_bytes_available ( ctx ) < 1 );
if ( 1 == rtkbase_generic_read( ctx, app_buf, 1 ) )
{
if ( RTKBASE_HEADER_0 == app_buf[ 0 ] )
{
break;
}
}
}
// wait until a header byte 1 and packet size bytes are available for read
while ( rtkbase_rx_bytes_available ( ctx ) < 2 );
if ( 2 != rtkbase_generic_read( ctx, &app_buf[ 1 ], 2 ) )
{
return RTKBASE_ERROR;
}
if ( RTKBASE_HEADER_1 != ( app_buf[ 1 ] & 0xFC ) )
{
return RTKBASE_ERROR;
}
app_buf_len = ( ( uint16_t ) ( app_buf[ 1 ] & 0x03 ) << 8 ) + app_buf[ 2 ] + 6; // Header + size + payload bytes + CRC bytes
// wait until payload and CRC bytes are available for read
while ( rtkbase_rx_bytes_available ( ctx ) < ( app_buf_len - 3 ) );
if ( ( app_buf_len - 3 ) != rtkbase_generic_read( ctx, &app_buf[ 3 ], ( app_buf_len - 3 ) ) )
{
return RTKBASE_ERROR;
}
// The CRC across the whole packet should sum to zero (remainder)
if ( 0 == rtkbase_calculate_crc24( app_buf, app_buf_len ) )
{
uint16_t rtcm3_msg_type = ( ( uint16_t ) app_buf[ 3 ] << 4 ) | ( ( app_buf[ 4 ] >> 4 ) & 0x0F ); // 12-bit message type
log_printf ( &logger, "\r\n\n RTCM3 -> Type: %u; Size: %u;\r\n", rtcm3_msg_type, app_buf_len );
for ( int32_t cnt = 0; cnt < app_buf_len; cnt++ )
{
log_printf( &logger, " %.2X", ( uint16_t ) app_buf[ cnt ] );
if ( ( cnt % 16 ) == 15 )
{
log_printf( &logger, "\r\n" );
}
}
return RTKBASE_OK;
}
return RTKBASE_ERROR;
}
// ------------------------------------------------------------------------ END
