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STM32F101xx and STM32F103xx medium- and high-density devices: advanced I²C examples

Application Note

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Last Updated: 19/09/2008

Pages: 14

Related Datasheets

Low-density performance line, ARM-based 32-bit MCU with 16 or 32 KB Flash, USB, CAN, 6 timers, 2 ADCs, 6 communication interfaces

Medium-density access line, ARM-based 32-bit MCU with 64 or 128 KB Flash, 6 timers, ADC and 7 communication interfaces

Medium-density performance line ARM-based 32-bit MCU with 64 or 128 KB Flash, USB, CAN, 7 timers, 2 ADCs, 9 communication interfaces

Related Information

Advanced I²C examples for STM32F101xx and STM32F103xx medium- and high-density

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AN2824 Application note
STM32F101xx and STM32F103xx medium- and high-density devices: advanced I²C examples
Introduction
The aim of this application note is to provide examples that cover the four I2C communication modes in which STM32F10xxx microcontrollers can operate, that is, slave transmitter, slave receiver, master transmitter and master receiver. This application note applies to STM32F101xx and STM32F103xx medium- and highdensity microcontrollers that feature two I2C interfaces (controllers). In the rest of the document, these devices will be referred to as STM32F10xxx. The application note is split into two parts. In the first part, the examples are focussed on the basic configuration of the four modes (data transfer involving the I2C interface only). The second part gives practical and advanced examples in a "real" application (involving other STM32F10xxx-controlled resources: multislave communication, ADC conversion, data display, power modes, temperature sensor, etc.). These examples are implemented with interrupts and bus error management.

September 2008

Rev 1

1/14
www.st.com

Contents

AN2824

Contents
1 Example 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 1.2 1.3 1.4 1.5 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Hardware environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Example description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Firmware details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 How to run the example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2

Example 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1 2.2 2.3 2.4 2.5 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Hardware environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Example 2 description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Firmware details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 How to run the example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3

Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

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List of figures

List of figures
Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Hardware connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Example 1 description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Example1 directory structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Hardware connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Example 2 description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Example 2 directory structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

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Example 1

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1
Note:

Example 1
Please keep in mind that this application note applies to STM32F101xx and STM32F103xx medium- and high-density microcontrollers that feature two I2C interfaces (controllers). In the rest of the document, these devices will be referred to as STM32F10xxx for convenience.

1.1

Overview
In this example, an I2C communication is set up between two STM32F10xxx devices. The first device is operating as a master transmitter/receiver and the second one, as a slave transmitter/receiver. Table 1: Interrupt events covered by example 1 gives the list of the interrupt events covered by this example. In this example, "STM32F10xxx I2C1" or "I2C1" is used to refer to the I2C1 interface of the device while "STM32F10xxx I2C2" or "I2C2" refers to the I2C2 interface. For more details, please refer to the medium- and high-density STM32F101xx and STM32F103xx datasheets and reference manual available from: http://www.st.com/stm32.
Table 1. Interrupt events covered by example 1 Interrupt event Star t bit sent (Master) Address sent (Master) or address matched (Slave) ITEVFEN Stop received (Slave) Data byte transfer finished Receive buffer not empty ITEVFEN and ITBUFEN Transmit buffer empty Bus error ITERREN Acknowledge failure Enable control bit

1.2

Hardware environment
Figure 1 shows the hardware connection between the I2C1 of an STM32F10xxx and the I2C2 of another STM32F10xxx. The I2C1 and I2C2 data lines (SDA) are connected together. The I2C1 and I2C2 clock (SCL) lines are also connected together. A pull-up resistor is connected to each line (I2C1 SDA and I2C1 SCL). There are no specific boards (single printed-circuit board) fitted with two STM32F10xxx devices, so we simply connected two STM3210B-EVAL boards together as shown in Figure 1: Hardware connection.

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AN2824 Figure 1. Hardware connection
3.3 V 4.7 k 3.3 V 4.7 k

Example 1

STM3210B-EVAL

I2C1 SCL I2C1 SDA

I2C2 SCL I2C2 SDA

STM32F10xxx Master

STM32F10xxx Slave

STM3210B-EVAL

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1.3

Example description
The Master transmits a buffer of bytes to the Slave. The buffer size is predetermined by the user (in the provided firmware, the buffer size is 16 bytes). The buffer received by the Slave is compared with the originally sent buffer and then their elements are incremented by 2 and re-sent to the Master. The buffer received by the Master is compared with the buffer sent by the Slave. This sequence can be relaunched by pressing the Key push-button connected to EXTI Line9 on the STM3210B-EVAL board operating as Master.

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Example 1 Figure 2. Example 1 description

AN2824

Press the Key push-button on the Master board (this triggers the EXTI line 9 interrupt)

The master generates the Start condition and sends the Slave address for a write operation

The Master sends a buffer of 16 bytes. On reception by the Slave, this buffer is compared to the original one sent by the Master

The Master sends another Start condition and sends the Slave address for a read operation

The Slave sends a buffer of 16 bytes. On reception by the Master, this buffer is compared to the original buffer sent by the Slave

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1.4

Firmware details
The example 1 firmware is structured as follows:

Slave folder: contains the Slave project and the corresponding source and header files. main.c: file in which the system clocks, I2C2 and interrupts are configured stm32f10x_it.c: file in which the I2C2 event (slave transmitter/receiver events) and error (acknowledge failure and bus error) interrupts are handled stm32f10x_it.h: headers of the interrupt handlers stm32f10x_conf.h: configuration file

Master folder: contains the Master project and the corresponding source and header files. main.c: file in which the system clocks, I2C1, EXTI line 9 and standard interrupts are configured stm32f10x_it.c: file in which the I2C1 event (master transmitter/receiver events) interrupts are handled stm32f10x_it.h: Headers of the interrupt handlers stm32f10x_conf.h: configuration file

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AN2824 Figure 3. Example1 directory structure
Example 1 Master Project

Example 1

Slave

Project
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1.5

How to run the example
In order to run the example successfully, go through the following steps:

Load the Slave project into board 1 Load the Master project into board 2 Run the code in board 1 Run the code in board 2 Press the PB9 push-button on board 2 in order to launch the communication.

You can either use an oscilloscope to visualize the data frames or simply read the buffers received by the Slave and the Master using the debugger.

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Example 2

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2
2.1

Example 2
Overview
In this example, I2C communication is performed between three STM32F10xxx microcontrollers. One device is operating as the Master receiver and the other two are operating as Slave transmitters. As mentioned in Section 1.1: Overview, "STM32F10xxx I2C1" or "I2C1" is used to refer to the I2C1 interface of an STM32F10xxx microcontroller with two I2C controllers and "STM32F10xxx I2C2" or "I2C2" refers to the I2C2 interface of another STM32F10xxx microcontroller also featuring two I2C controllers.

2.2

Hardware environment
Figure 4: Hardware connection shows the connection between an STM32F10xxx I2C1 and two STM32F10xxx I2C2s. The I2C1 and I2C2 data (SDA) lines are connected together. The I2C1 and I2C2 clock (SCL) lines are also connected together. A pull-up resistor is connected to each line (SDA and SCL). Like in the case of example 1, there is not a specific board (single PCB) fitted with three STM32F10xxx devices, so we chose to connect an STM3210B-EVAL board (Master) to an IAR board (STM32-SK Rev B) (Slave 1) and a Keil board (MCBSTM32 v1.1) (Slave 2). For more details about the boards used in these examples, please refer to the following links:

http://www.keil.com for the MCBSTM32 board http://www.iar.com for the STM32-SK board http://www.st.com/stm32 for the STM3210B-EVAL board

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AN2824 Figure 4. Hardware connection
3.3 V 3.3 V

Example 2

4.7 k

4.7 k

STM3210B-EVAL

I2C1 SDA

I2C2 SDA

I2C1 SCL
STM32F10xxx Master

I2C2 SCL
STM32F10xxx Slave 2

I2C2 SDA

I2C2 SCL
STM32F10xxx Slave 1

IAR board : STM32-SK Rev B.
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2.3

Example 2 description
Slave 1 (IAR board) sends the converted values of the ADC1 channel 15 (ADC1_CH15) to the Master. ADC1_CH15 is connected to the potentiometer on the board. Slave 2 sends the temperature values to the Master, using the on-chip temperature sensor that is internally connected to ADC1_CH16. The Start condition is generated within a timer interrupt triggered once every second. Consequently, both Slaves send data alternately every second, approximately. Once the Master has generated the Start condition and sent the Slave address: if Slave1 is addressed, ADC1_CH15 conversions are launched. The number of conversions is to be fixed by the user. In the example, 16 conversions are carried out. DMA1 channel 1 is used to transfer the data to the I2C2_Buffer_Tx buffer, which is then sent to the Master. if Slave2 is addressed, ADC1_CH16 conversions are launched. The number of conversions is to be fixed by the user. In the example, 16 conversions are carried out. DMA1 channel 1 is used to transfer the data to a table named Buffer. Then the I2C2_Buffer_Tx buffer is filled with the temperature values using elements in the Buffer table and the formula provided in the device reference manual. I2C2_Buffer_Tx buffer is then sent to the Master. When the transmission is complete, the Slaves enter the Sleep mode using WFI. When a Start condition is generated by the Master and the Slave address is sent, the Slave address match will trigger an I2C interrupt that will wake up the corresponding Slave.

keil board : MCBSTM32

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Example 2 After receiving the data, the Master transmits them to the display interface. Note:

AN2824

The display on the STM3210B-EVAL is connected to the SPI whereas on the STM3210EEVAL (high-density evaluation board) it is connected to the FSMC. So to be able to use the provided firmware with the STM3210E-EVAL board, it is first necessary to update it. Figure 5. Example 2 description

Timer interrupt is triggered (Master)

The Master generates the Start condition and sends Slave 1 address for a read operation

Slave 1 sends a buffer of 16 bytes, which corresponds to the values converted by ADC1_CH15

After receiving the data, the Master transmits them to the TFT display

The timer interrupt is triggered again (Master)

The Master generates the Start condition and sends Slave 2 address for a read operation

Slave 2 sends a buffer of 16 bytes, which corresponds to the chip temperature (obtained from the on-chip temperature sensor)

After receiving the data, the Master transmits them to the TFT display

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AN2824

Example 2

2.4

Firmware details
The example 2 firmware is structured as follows:

Slave1 folder: it contains the Slave 1 project and the corresponding source and header files: main.c: file in which the system clocks, I2C2, DMA1 channel 1, ADC1_CH15 and interrupts are configured stm32f10x_it.c: file where the I2C2 event (slave receiver events) and error (acknowledge failure and bus error) interrupts are handled stm32f10x_it.h: headers of the interrupt handlers stm32f10x_conf.h: configuration file

Slave2 folder: it contains the Slave 2 project and the corresponding source and header files: main.c: file in which the system clocks, I2C2, DMA1 Channel1, ADC1 channel 16 and interrupts are configured. stm32f10x_it.c: file where the I2C2 event (slave receiver events) and error (acknowledge failure and bus error) interrupts are handled stm32f10x_it.h: headers of the interrupt handlers stm32f10x_conf.h: configuration file

Master folder: it contains the Master project and the corresponding source and header files. It is subdivided into three subfolders, the: Source subfolder contains: main.c: file where the system clocks, I2C1, TIM2, LCD and interrupts are configured. stm32f10x_it.c: file where I2C1 events (master receiver events) and TIM2 interrupts are programmed. lcd.c: it contains some LCD routines for the AM-240320LTNQW00H liquid crystal display module of the STM3210B-EVAL. lcd_config.c: Include subfolder contains: main.h: header file for main.c stm32f10x_it.h: header file for stm32f10x_it.c lcd.h: header file for lcd.c lcd_config.h: header file for lcd_config.c fonts.h: it contains the lcd fonts size definition Project subfolder contains preconfigured projects.

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Example 2 Figure 6. Example 2 directory structure
Example 2 Slave1 Project

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Slave2

Project

Master

Include Project Source
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2.5

How to run the example
To run the example successfully, go through the following steps:

Load the Slave 1 driver into board 1 Load the Slave 2 driver into board 2 Load the Master driver into board 3 Run the code in board 1 Run the code in board 2 Run the code in board 3

Now, the values converted by Slave1 ADC1_CH15 and the temperature values provided by Slave 2 are displayed alternately and continuously, every second approximately, on the master board TFT display. Note: The user can change the firmware so as to launch the I2C communication with a different periodicity (in the example, periodicity = T = 1 s). Be careful when selecting T because it takes time to display the received bytes on the TFT display. In fact, the selected periodicity should be less than or equal to T otherwise a mixture of ADC1_CH15 (Slave 1) and temperature values (Slave 2) will be displayed.

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Revision history

3

Revision history
Table 2.
Date 18-Sep-2008

Document revision history
Revision 1 Initial release. Changes

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Document Number: 15021



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