Establish long-distance wireless transmission with RFM75 and STM32F302VC
Stay connected without the hassle
Published Jul 22, 2025
Click board™
ISM Click
Dev. board
CLICKER 4 for STM32F302VCT6
Compiler
NECTO Studio
MCU
STM32F302VC
Unleash the potential of your solution and get efficient, fast, and reliable wireless communication
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Hardware Overview
How does it work?
ISM Click is based on the RFM75, a low-power, high-performance 2.4GHz GFSK transceiver operating in the worldwide ISM frequency band from 2400MHz to 2527MHz from RF Solutions. The RFM75 operates in TDD mode, either as a transmitter or as a receiver. Burst mode transmission and up to 2Mbps air data rate make it suitable for ultra-low power consumption applications. The embedded packet processing engines enable their entire operation with a simple MCU as a radio system. Auto re-transmission and auto acknowledge giving reliable link without any MCU interference. A transmitter and receiver must be programmed with the same RF channel frequency to communicate, supporting a programmable air
data rate of 250Kbps, 1Mbps, or 2Mbps. The RF channel frequency determines the center of the channel used by RFM75. The RF_CH register, in register bank 0, sets the frequency according to the following formula F0= 2400 + RF_CH (MHz), where the resolution of the RF channel frequency is 1MHz. ISM Click communicates with MCU using the standard SPI serial interface that operates at clock rates up to 8 MHz. In power-down mode, RFM75 is in Sleep mode with minimal current consumption. The SPI interface is still active in this mode, and all register values are available by the SPI interface. This Click board™ also has a yellow LED indicator routed on the INT pin of the mikroBUS™ socket (provide the user with feedback after
a successfully received package) and a chip-enable function routed on the RST pin of the mikroBUS™ which activates TX or RX mode of the RFM75. Besides, it also has two additional LED indicators, a red and blue LED routed on the AN and PWM pins of the mikroBUS™ socket. The user can use it for visual indication when sending or receiving data. This Click board™ can only be operated with a 3.3V logic voltage level. 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 an example code that can be used as a reference for further development.
Features overview
Development board
Clicker 4 for STM32F3 is a compact development board designed as a complete solution, you can use it to quickly build your own gadgets with unique functionalities. Featuring a STM32F302VCT6, four mikroBUS™ sockets for Click boards™ connectivity, power managment, and more, it represents a perfect solution for the rapid development of many different types of applications. At its core, there is a STM32F302VCT6 MCU, a powerful microcontroller by STMicroelectronics, based on the high-
performance Arm® Cortex®-M4 32-bit processor core operating at up to 168 MHz frequency. It provides sufficient processing power for the most demanding tasks, allowing Clicker 4 to adapt to any specific application requirements. Besides two 1x20 pin headers, four improved mikroBUS™ sockets represent the most distinctive connectivity feature, allowing access to a huge base of Click boards™, growing on a daily basis. Each section of Clicker 4 is clearly marked, offering an intuitive and clean interface. This makes working with the development
board much simpler and thus, faster. The usability of Clicker 4 doesn’t end with its ability to accelerate the prototyping and application development stages: it is designed as a complete solution which can be implemented directly into any project, with no additional hardware modifications required. Four mounting holes [4.2mm/0.165”] at all four corners allow simple installation by using mounting screws. For most applications, a nice stylish casing is all that is needed to turn the Clicker 4 development board into a fully functional, custom design.
Microcontroller Overview
MCU Card / MCU
Architecture
ARM Cortex-M4
MCU Memory (KB)
256
Silicon Vendor
STMicroelectronics
Pin count
100
RAM (Bytes)
40960
Used MCU Pins
mikroBUS™ mapper
Take a closer look
Click board™ Schematic
Step by step
Project assembly
Start by selecting your development board and Click board™. Begin with the CLICKER 4 for STM32F302VCT6 as your development board.
Software Support
Library Description
This library contains API for ISM Click driver.
Key functions:
ism_cfg_setup- Config Object Initialization function.ism_init- Initialization function.ism_default_cfg- Click Default Configuration 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 Ism Click example
*
* # Description
* This library contains API for the ISM Click driver.
* This example transmits/receives and processes data from ISM Clicks.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initializes driver and performs the default configuration.
*
* ## Application Task
* Transmitter/Receiver task depends on uncommented code.
* Receiver logging each received byte to the UART for data logging,
* while transmitter send messages every 1 second.
*
* @author Nenad Filipovic
*
*/
#include "board.h"
#include "log.h"
#include "ism.h"
// Comment out the line below in order to switch the application mode to receiver
#define DEMO_APP_TRANSMITTER
static ism_t ism;
static log_t logger;
static uint8_t demo_message_1[ 9 ] = { 'M', 'i', 'k', 'r', 'o', 'E', 13, 10, 0 };
static uint8_t demo_message_2[ 12 ] = { 'I', 'S', 'M', ' ', 'C', 'l', 'i', 'c', 'k', 13, 10, 0 };
void application_init ( void )
{
log_cfg_t log_cfg; /**< Logger config object. */
ism_cfg_t ism_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.
ism_cfg_setup( &ism_cfg );
ISM_MAP_MIKROBUS( ism_cfg, MIKROBUS_1 );
if ( SPI_MASTER_ERROR == ism_init( &ism, &ism_cfg ) )
{
log_error( &logger, " Application Init Error. " );
log_info( &logger, " Please, run program again... " );
for ( ; ; );
}
ism_default_cfg ( &ism );
Delay_ms ( 100 );
#ifdef DEMO_APP_TRANSMITTER
ism_switch_tx_mode( &ism );
log_printf( &logger, " Application Mode: Transmitter\r\n" );
#else
ism_switch_rx_mode( &ism );
log_printf( &logger, " Application Mode: Receiver\r\n" );
#endif
log_info( &logger, " Application Task " );
}
void application_task ( void )
{
#ifdef DEMO_APP_TRANSMITTER
ism_transmit_packet( &ism, ISM_CMD_W_TX_PAYLOAD_NOACK, demo_message_1, 9 );
log_printf( &logger, " Tx : %s", demo_message_1 );
Delay_ms ( 1000 );
ism_transmit_packet( &ism, ISM_CMD_W_TX_PAYLOAD_NOACK, demo_message_2, 12 );
log_printf( &logger, " Tx : %s", demo_message_2 );
Delay_ms ( 1000 );
#else
uint8_t rx_buf[ ISM_MAX_PACKET_LEN ] = { 0 };
ism_receive_packet( &ism, &rx_buf[ 0 ] );
if ( rx_buf[ 0 ] )
{
log_printf( &logger, " Rx : %s", rx_buf );
}
#endif
}
int main ( void )
{
/* Do not remove this line or clock might not be set correctly. */
#ifdef PREINIT_SUPPORTED
preinit();
#endif
application_init( );
for ( ; ; )
{
application_task( );
}
return 0;
}
// ------------------------------------------------------------------------ END
Additional Support
Resources
Category:2.4 GHz Transceivers
