Measure RF signal strength with the help of LT5581 and STM32F103RB
Charting the invisible: RF meters in action
Published Oct 08, 2024
Click board™
RF Meter 3 Click
Dev Board
Nucleo 64 with STM32F103RB MCU
Compiler
NECTO Studio
MCU
STM32F103RB
Dive into the world of RF meters, where you'll learn to measure invisible radio frequency waves and harness their potential for various applications
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Hardware Overview
How does it work?
RF Meter 3 Click is based on the LT5581, an RMS power detector with a 40dB dynamic range from Analog Devices. Users can use an RF power meter like this one to measure and document pulsed RF signals, noise-like signals, and pseudorandom signals. The RMS detector uses a proprietary technique to accurately measure the RF power from 2GHz up to 2.6GHz. Moreover, the LT5581 offers exceptional accuracy over its wide operating temperature range. Its RMS measurement capability provides accurate RF power readings within ±0.2dB regardless of waveforms with high crest-factor modulated content, multi-carrier, or multitone. The LT5581 combines a proprietary
high-speed power measurement subsystem with an internal 150kHz low pass averaging filter and an output voltage buffer in a completely integrated solution to achieve an accurate average power measurement of the high crest factor modulated RF signals. The resulting output voltage is directly proportional to the average RF input power in dBm. This Click board™ uses two mikroBUS™ pins for direct control. The Enable pin, labeled as EN and routed to the CS pin of the mikroBUS™ socket, optimizes power consumption and is used for power ON/OFF purposes (Shutdown feature). When its Enable input pin is pulled low, the LT5581 draws a typical shutdown current of 0.2uA and a
maximum of 6uA. As mentioned before, the resulting output voltage of the LT5581 is sent directly to an analog pin of the mikroBUS™ socket labeled as AN for MCU to read further and analyze RF signal data. 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 STM32F103RB 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-M3
MCU Memory (KB)
128
Silicon Vendor
STMicroelectronics
Pin count
64
RAM (Bytes)
20480
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 STM32F103RB 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 RF Meter 3 Click driver.
Key functions:
rfmeter3_enable_device- This function enables device by setting EN pin to HIGH logic level.rfmeter3_disable_device- This function disables device by setting EN pin to LOW logic level.rfmeter3_get_rf_input_power- This function reads the voltage from AN pin and converts it to RF input power in dBm.
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 RF Meter 3 Click Example.
*
* # Description
* This example demonstrates the use of RF Meter 3 click board.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initializes the driver and enables the click board.
*
* ## Application Task
* Measures the RF input signal power in dBm and displays the results on the USB UART every 100ms.
*
* @author Stefan Filipovic
*
*/
#include "board.h"
#include "log.h"
#include "rfmeter3.h"
static rfmeter3_t rfmeter3; /**< RF Meter 3 Click driver object. */
static log_t logger; /**< Logger object. */
void application_init ( void )
{
log_cfg_t log_cfg; /**< Logger config object. */
rfmeter3_cfg_t rfmeter3_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.
rfmeter3_cfg_setup( &rfmeter3_cfg );
RFMETER3_MAP_MIKROBUS( rfmeter3_cfg, MIKROBUS_1 );
if ( ADC_ERROR == rfmeter3_init( &rfmeter3, &rfmeter3_cfg ) )
{
log_error( &logger, " Application Init Error. " );
log_info( &logger, " Please, run program again... " );
for ( ; ; );
}
rfmeter3_enable_device ( &rfmeter3 );
log_info( &logger, " Application Task " );
}
void application_task ( void )
{
float rfmeter3_rf_input_power = 0;
if ( RFMETER3_ERROR != rfmeter3_get_rf_input_power ( &rfmeter3, &rfmeter3_rf_input_power ) )
{
log_printf( &logger, " RF Input Power: %.2f dBm\r\n", rfmeter3_rf_input_power );
Delay_ms( 100 );
}
}
void main ( void )
{
application_init( );
for ( ; ; )
{
application_task( );
}
}
// ------------------------------------------------------------------------ END
