Bridge the voltage gap between I2C devices with LLC solution and STM32F091RC
Leveling up the logic: Precise I2C signal conversion!
Published Feb 26, 2024
Click board™
LLC-I2C Click
Dev Board
Nucleo-64 with STM32F091RC MCU
Compiler
NECTO Studio
MCU
STM32F091RC
Empower your projects with the ability to seamlessly convert logic levels between I2C devices, optimizing communication, reducing compatibility issues, and simplifying the integration of components with varying voltage thresholds
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Hardware Overview
How does it work?
LLC-I2C Click does not use an integrated circuit, as already mentioned. With ICs avoided completely, there are some benefits gained: the overall cost of the LLC circuit is greatly reduced, a more robust MOSFET solution reduces the failure rate, and when powered off, both the low voltage and the high voltage sides are isolated from one another (by non-conductive MOSFETs). This type of circuit is sometimes referred to as a level shifting or level translating circuit and it is often necessary when the I2C slave device (typically a sensor IC) uses different logic voltage levels for the I2C communication than the master device, which is a host microcontroller in most cases. The conversion of this circuitry is bi-directional, which makes it suitable to be used with the I2C communication protocol. The I2C protocol was first introduced by NXP Semiconductors (formerly Philips Semiconductors), in 1982. They also introduced
an application note that explains the operation of the LLC circuit in more details. The circuit is divided into low-side and high-side sections for future reference, although the circuit is symmetrical and can be used in both directions. When there is no communication going on, both gates and sources of the MOSFETs are pulled up to their specific reference voltage levels. This will turn OFF both MOSFETs since there is no gate-source voltage difference (e.g. VG=VS=VSL). Since the I2C is operated by asserting its bus lines to a LOW logic level, when the source terminal of the MOSFET on one side (e.g. high-side) is driven to a LOW logic level, its VGS potential will rise since the gate voltage is fixed. When the VGS reaches the threshold voltage (1.2V typically for the used transistors), the MOSFET will turn ON, conducting current through the body diode of the opposite-side (low-side) MOSFET, which will become
directly polarized. This mechanism can be used to convert signal levels in both directions, within the whole operating range of the used MOSFETs. The reference voltage for the high-side can be selected by using the SMD jumper labeled as VCC SEL. The pull-up voltage for the high-side can be selected from the mikroBUS™ power rails, so it can be either 3.3V or 5V. For the low-side, an arbitrary reference voltage can be applied to the VSL pin of the J1 header, respecting the maximum voltage rating. J1 is the standard, 2.54mm pin-header. The low-side I2C bus pins are also routed to the J1 header, allowing an external device to be connected (using the standard wire-jumpers). As already mentioned, the low-side can actually use higher voltage levels than the master, but in most usage scenarios, it will be lower than the master, thus the terminology.
Features overview
Development board
Nucleo-64 with STM32F091RC 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)
256
Silicon Vendor
STMicroelectronics
Pin count
64
RAM (Bytes)
32768
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 STM32F091RC MCU as your development board.
Track your results in real time
Application Output
1. Application Output - In Debug mode, the 'Application Output' window enables real-time data monitoring, offering direct insight into execution results. Ensure proper data display by configuring the environment correctly using the provided tutorial.
2. UART Terminal - Use the UART Terminal to monitor data transmission via a USB to UART converter, allowing direct communication between the Click board™ and your development system. Configure the baud rate and other serial settings according to your project's requirements to ensure proper functionality. For step-by-step setup instructions, refer to the provided tutorial.
3. Plot Output - The Plot feature offers a powerful way to visualize real-time sensor data, enabling trend analysis, debugging, and comparison of multiple data points. To set it up correctly, follow the provided tutorial, which includes a step-by-step example of using the Plot feature to display Click board™ readings. To use the Plot feature in your code, use the function: plot(*insert_graph_name*, variable_name);. This is a general format, and it is up to the user to replace 'insert_graph_name' with the actual graph name and 'variable_name' with the parameter to be displayed.
Software Support
Library Description
This library contains API for LLC-I2C Click driver.
Key functions:
llci2c_generic_write- This function writes data to the desired registerllci2c_generic_read- This function reads data from the desired register
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
* \brief LlcI2c Click example
*
* # Description
* This click can be utilized as the level converter for logic signals. The topology of this
* logic level conversion (LLC) circuit is perfectly suited for the bi-directional I2C communication.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initialization driver init
*
* ## Application Task
* Reads the temperature from the Thermo 7 click board and logs data to UART.
*
* *note:*
* <pre>
* Connection between Thermo 7 and I2C-LLC is made through I2C interface.
* You can connect a Thermo 7 click and I2C-LLC click with the wires to make connection between click boards.
* We use the Thermo 7 click to demonstrate the functions of the I2C-LLC click.
* </pre>
*
* \author MikroE Team
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "llci2c.h"
// ------------------------------------------------------------------ VARIABLES
static llci2c_t llci2c;
static log_t logger;
// ------------------------------------------------------ APPLICATION FUNCTIONS
void application_init ( void )
{
log_cfg_t log_cfg;
llci2c_cfg_t cfg;
/**
* 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.
llci2c_cfg_setup( &cfg );
LLCI2C_MAP_MIKROBUS( cfg, MIKROBUS_1 );
llci2c_init( &llci2c, &cfg );
}
void application_task ( void )
{
// Thermo 7 measurement Temperature
uint8_t write_reg = 0x00;
uint8_t read_reg[ 2 ] = { 0 };
float temp_msb;
uint8_t temp_lsb;
llci2c_generic_read ( &llci2c, write_reg, read_reg, 2 );
temp_msb = read_reg[ 0 ];
temp_lsb = read_reg[ 1 ] & 0xF0;
if ( temp_lsb & 0x80 ) temp_msb += 0.50;
if ( temp_lsb & 0x40 ) temp_msb += 0.25;
if ( temp_lsb & 0x20 ) temp_msb += 0.125;
if ( temp_lsb & 0x10 ) temp_msb += 0.0625;
log_info( &logger, " Ambient temperature : %.2f C", temp_msb );
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
/*!
* \file
* \brief LlcI2c Click example
*
* # Description
* This click can be utilized as the level converter for logic signals. The topology of this
* logic level conversion (LLC) circuit is perfectly suited for the bi-directional I2C communication.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initialization driver init
*
* ## Application Task
* Reads the temperature from the Thermo 7 click board and logs data to UART.
*
* *note:*
* <pre>
* Connection between Thermo 7 and I2C-LLC is made through I2C interface.
* You can connect a Thermo 7 click and I2C-LLC click with the wires to make connection between click boards.
* We use the Thermo 7 click to demonstrate the functions of the I2C-LLC click.
* </pre>
*
* \author MikroE Team
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "llci2c.h"
// ------------------------------------------------------------------ VARIABLES
static llci2c_t llci2c;
static log_t logger;
// ------------------------------------------------------ APPLICATION FUNCTIONS
void application_init ( void )
{
log_cfg_t log_cfg;
llci2c_cfg_t cfg;
/**
* 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.
llci2c_cfg_setup( &cfg );
LLCI2C_MAP_MIKROBUS( cfg, MIKROBUS_1 );
llci2c_init( &llci2c, &cfg );
}
void application_task ( void )
{
// Thermo 7 measurement Temperature
uint8_t write_reg = 0x00;
uint8_t read_reg[ 2 ] = { 0 };
float temp_msb;
uint8_t temp_lsb;
llci2c_generic_read ( &llci2c, write_reg, read_reg, 2 );
temp_msb = read_reg[ 0 ];
temp_lsb = read_reg[ 1 ] & 0xF0;
if ( temp_lsb & 0x80 ) temp_msb += 0.50;
if ( temp_lsb & 0x40 ) temp_msb += 0.25;
if ( temp_lsb & 0x20 ) temp_msb += 0.125;
if ( temp_lsb & 0x10 ) temp_msb += 0.0625;
log_info( &logger, " Ambient temperature : %.2f C", temp_msb );
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
/*!
* \file
* \brief LlcI2c Click example
*
* # Description
* This click can be utilized as the level converter for logic signals. The topology of this
* logic level conversion (LLC) circuit is perfectly suited for the bi-directional I2C communication.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initialization driver init
*
* ## Application Task
* Reads the temperature from the Thermo 7 click board and logs data to UART.
*
* *note:*
* <pre>
* Connection between Thermo 7 and I2C-LLC is made through I2C interface.
* You can connect a Thermo 7 click and I2C-LLC click with the wires to make connection between click boards.
* We use the Thermo 7 click to demonstrate the functions of the I2C-LLC click.
* </pre>
*
* \author MikroE Team
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "llci2c.h"
// ------------------------------------------------------------------ VARIABLES
static llci2c_t llci2c;
static log_t logger;
// ------------------------------------------------------ APPLICATION FUNCTIONS
void application_init ( void )
{
log_cfg_t log_cfg;
llci2c_cfg_t cfg;
/**
* 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.
llci2c_cfg_setup( &cfg );
LLCI2C_MAP_MIKROBUS( cfg, MIKROBUS_1 );
llci2c_init( &llci2c, &cfg );
}
void application_task ( void )
{
// Thermo 7 measurement Temperature
uint8_t write_reg = 0x00;
uint8_t read_reg[ 2 ] = { 0 };
float temp_msb;
uint8_t temp_lsb;
llci2c_generic_read ( &llci2c, write_reg, read_reg, 2 );
temp_msb = read_reg[ 0 ];
temp_lsb = read_reg[ 1 ] & 0xF0;
if ( temp_lsb & 0x80 ) temp_msb += 0.50;
if ( temp_lsb & 0x40 ) temp_msb += 0.25;
if ( temp_lsb & 0x20 ) temp_msb += 0.125;
if ( temp_lsb & 0x10 ) temp_msb += 0.0625;
log_info( &logger, " Ambient temperature : %.2f C", temp_msb );
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
