Expand I2C bus into four independent channels with TPT29546A and STM32G071RB
Four-channel I2C switch with a reset function
Published Mar 26, 2025
Click board™
I2C MUX 8 Click
Dev. board
Nucleo 64 with STM32G071RB MCU
Compiler
NECTO Studio
MCU
STM32G071RB
Expand I2C communication with four independent channels for industrial automation, telecom routers, and multi-device system
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Hardware Overview
How does it work?
I2C MUX 8 Click is based on the TPT29546A, a four-channel I2C switch with a reset function from 3PEAK. This bidirectional translating switch allows a single upstream I2C bus (SCL/SDA pair) to be expanded into four independent downstream channels. The selection of active channels is controlled via a programmable register, making it highly flexible for applications that require multiple I2C devices to operate simultaneously without interference. I2C MUX 8 Click is a solution particularly valuable in systems where multiple I2C devices need to coexist without address conflicts. It is commonly used in servers and storage solutions, telecom switching equipment such as routers, and industrial automation. Additionally, it is an ideal choice for products that require multiple identical
I2C devices, such as temperature sensors, ensuring efficient and conflict-free operation in complex embedded systems. I2C MUX 8 Click communicates with MCU using the standard I2C 2-Wire interface that supports Standard-Mode (100 kHz) and Fast-Mode (400 kHz) operation. The TPT29546A has a 7-bit I2C address with the first five MSBs fixed to 1110. The address pins A0, A1, and A2, are programmed by the user and determine the value of the last three LSBs of the I2C address, which can be selected by onboard SMD jumpers labeled as ADDR SEL, allowing selection of the I2C address LSBs. A notable feature of the TPT29546A is its built-in recovery mechanism. If any of the downstream I2C buses become stuck in a LOW state, the active-low reset function (RST pin) can
be used to restore normal operation. By pulling the RST pin LOW, the internal I2C state machine is reset, and all channels are deselected. Additionally, the device includes an internal power-on reset feature, ensuring a stable startup by resetting all channels to their default state. 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 STM32G071RB 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-M0
MCU Memory (KB)
128
Silicon Vendor
STMicroelectronics
Pin count
64
RAM (Bytes)
36864
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
Click board™ Schematic
Step by step
Project assembly
Start by selecting your development board and Click board™. Begin with the Nucleo 64 with STM32G071RB MCU as your development board.
Software Support
Library Description
I2C MUX 8 Click demo application is developed using the NECTO Studio, ensuring compatibility with mikroSDK's open-source libraries and tools. Designed for plug-and-play implementation and testing, the demo is fully compatible with all development, starter, and mikromedia boards featuring a mikroBUS™ socket.
Example Description
This example demonstrates the use of I2C MUX 8 Click board by reading the device ID of a 6DOF IMU 11 and Compass 3 Click boards connected to the channels 1 and 4 respectfully.
Key functions:
i2cmux8_cfg_setup- This function initializes Click configuration structure to initial values.i2cmux8_init- This function initializes all necessary pins and peripherals used for this Click board.i2cmux8_set_channel- This function sets the active channel and updates the slave address for communication.i2cmux8_read_channel- This function reads the currently selected channel.i2cmux8_i2c_read_reg- This function reads data from a specific register of the currently active I2C slave.
Application Init
Initializes the driver and resets the device.
Application Task
Reads the device ID of the connected Click boards. Channel 1 : 6DOF IMU 11 Click [slave address: 0x0E; reg: 0x00; id: 0x2D], Channel 4 : Compass 3 Click [slave address: 0x30; reg: 0x2F; id: 0x0C]. All data is being logged on the USB UART where you can check the device ID.
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 I2C MUX 8 Click example
*
* # Description
* This example demonstrates the use of I2C MUX 8 Click board by reading the
* device ID of a 6DOF IMU 11 and Compass 3 Click boards connected to
* the channels 1 and 4 respectfully.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initializes the driver and resets the device.
*
* ## Application Task
* Reads the device ID of the connected Click boards.
* Channel 1 : 6DOF IMU 11 Click [slave address: 0x0E; reg: 0x00; id: 0x2D],
* Channel 4 : Compass 3 Click [slave address: 0x30; reg: 0x2F; id: 0x0C].
* All data is being logged on the USB UART where you can check the device ID.
*
* @author Stefan Filipovic
*
*/
#include "board.h"
#include "log.h"
#include "i2cmux8.h"
#define DEVICE0_NAME "6DOF IMU 11 Click"
#define DEVICE0_POSITION I2CMUX8_CHANNEL_1
#define DEVICE0_SLAVE_ADDRESS 0x0E
#define DEVICE0_REG_ID 0x00
#define DEVICE0_ID 0x2D
#define DEVICE1_NAME "Compass 3 Click"
#define DEVICE1_POSITION I2CMUX8_CHANNEL_4
#define DEVICE1_SLAVE_ADDRESS 0x30
#define DEVICE1_REG_ID 0x2F
#define DEVICE1_ID 0x0C
static i2cmux8_t i2cmux8;
static log_t logger;
void application_init ( void )
{
log_cfg_t log_cfg; /**< Logger config object. */
i2cmux8_cfg_t i2cmux8_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.
i2cmux8_cfg_setup( &i2cmux8_cfg );
I2CMUX8_MAP_MIKROBUS( i2cmux8_cfg, MIKROBUS_1 );
if ( I2C_MASTER_ERROR == i2cmux8_init( &i2cmux8, &i2cmux8_cfg ) )
{
log_error( &logger, " Communication init." );
for ( ; ; );
}
i2cmux8_reset_device ( &i2cmux8 );
log_info( &logger, " Application Task " );
}
void application_task ( void )
{
uint8_t channel = 0, device_id = 0;
if ( I2CMUX8_OK == i2cmux8_set_channel ( &i2cmux8, DEVICE0_POSITION, DEVICE0_SLAVE_ADDRESS ) )
{
if ( I2CMUX8_OK == i2cmux8_read_channel ( &i2cmux8, &channel ) )
{
log_printf( &logger, " --- Channel %u --- \r\n", ( uint16_t ) channel );
}
if ( I2CMUX8_OK == i2cmux8_i2c_read_reg ( &i2cmux8, DEVICE0_REG_ID, &device_id, 1 ) )
{
log_printf( &logger, " %s - Device ID: 0x%.2X \r\n\n", ( char * ) DEVICE0_NAME, ( uint16_t ) device_id );
}
Delay_ms ( 1000 );
}
if ( I2CMUX8_OK == i2cmux8_set_channel ( &i2cmux8, DEVICE1_POSITION, DEVICE1_SLAVE_ADDRESS ) )
{
if ( I2CMUX8_OK == i2cmux8_read_channel ( &i2cmux8, &channel ) )
{
log_printf( &logger, " --- Channel %u --- \r\n", ( uint16_t ) channel );
}
if ( I2CMUX8_OK == i2cmux8_i2c_read_reg ( &i2cmux8, DEVICE1_REG_ID, &device_id, 1 ) )
{
log_printf( &logger, " %s - Device ID: 0x%.2X \r\n\n", ( char * ) DEVICE1_NAME, ( uint16_t ) device_id );
}
Delay_ms ( 1000 );
}
}
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:I2C
