I2C_OneBoard_AdvCommunication_DMAAndIT_Init Example Description

How to exchange data between an I2C master device in DMA mode and an I2C slave device in interrupt mode. The peripheral is initialized with LL unitary service functions to optimize for performance and size.

This example guides you through the different configuration steps by mean of LL API to configure GPIO, DMA and I2C peripherals using only one NUCLEO-C071RB.

The user can disable internal pull-up by opening ioc file.

For that, user can follow the procedure :

  1. Double click on the I2C_OneBoard_AdvCommunication_DMAAndIT_Init.ioc file
  2. When CUBEMX tool is opened, select System Core category
  3. Then in the configuration of GPIO/I2C1, change Pull-up to No pull-up and no pull-down for the both pins
  4. Same action in the configuration of GPIO/I2C2, change Pull-up to No pull-up and no pull-down for the both pins
  5. Last step, generate new code thanks to button “GENERATE CODE”

The example is updated with no pull on each pin used for I2C communication

I2C1 Peripheral is configured in Slave mode with EXTI (Clock 400Khz, Own address 7-bit enabled). I2C2 Peripheral is configured in Master mode with DMA (Clock 400Khz). GPIO associated to User push-button is linked with EXTI.

LED1 blinks quickly to wait for user-button press.

Example execution: Press the User push-button to initiate a write request by Master through Handle_I2C_Master_Transmit() or through Handle_I2C_Master_TransmitReceive() routine depends on Command Code type.

Command code type is decomposed in two categories :

  1. Action Command code :

    1. Type of command which need an action from Slave Device without send any specific answer)

    2. I2C sequence is composed like that :

           _____________________________________________________________________________________
          |_START_|_Slave_Address_|_Wr_|_A_|_Command_Code_BYTE_1_|_A_|_Command_Code_BYTE_2_|_A_|....
           ________________________________
          |_Command_Code_BYTE_M_|_A_|_STOP_|
      

First of all, through Handle_I2C_Master_Transmit() routine, Master device generate an I2C start condition with the Slave address and a write bit condition. When address Slave match code is received on I2C1, an ADDR interrupt occurs. I2C1 IRQ Handler routine is then checking Address Match Code and direction Write. This will allow Slave to enter in receiver mode and then acknowledge Master to send the Command code bytes through DMA. When acknowledge is received on I2C2, DMA transfer the Command code data from flash memory buffer to I2C2 TXDR register. This will allow Master to transmit a byte to the Slave. Each time a byte is received on I2C1 (Slave), an RXNE interrupt occurs and byte is stored into an internal buffer until a STOP condition. And so each time the Slave acknowledge the byte received, DMA transfer the next data from flash memory buffer to I2C2 TXDR register until Transfer completed. Master auto-generate a Stop condition when DMA transfer is achieved.

The STOP condition generate a STOP interrupt and initiate the end of reception on Slave side. I2C1 IRQ handler and Handle_I2C_Master_Transmit() routine are then clearing the STOP flag in both side.

LED1 is On if data are well sent and the Command Code sent to slave is print in the Terminal I/O.

  1. Request Command code :

    1. Type of command which need a specific data answer from Slave Device.

    2. I2C sequence is composed like that :

           _______ _______________ ________ _____________________ ___ _____________________ ___ ____
          |_START_|_Slave_Address_|_Wr_|_A_|_Command_Code_BYTE_1_|_A_|_Command_Code_BYTE_2_|_A_|....
           ______________________________________________________________________________
          |_Command_Code_BYTE_M_|_A_|_RESTART_|_Slave_Address_|_Rd_|_A_|_Data_BYTE_1_|_A_|...
           ___________________________________________
          |_Data_BYTE_2_|_A_|_Data_BYTE_N_|_NA_|_STOP_|
      

First of all, through Handle_I2C_Master_TransmitReceive() routine, Master device generate an I2C start condition with the Slave address and a write bit condition. When address Slave match code is received on I2C1, an ADDR interrupt occurs. I2C1 IRQ Handler routine is then checking Address Match Code and direction Write. This will allow Slave to enter in receiver mode and then acknowledge Master to send the Command code bytes through DMA. When acknowledge is received on I2C2, DMA transfer the Command code data from flash memory buffer to I2C2 TXDR register. This will allow Master to transmit a byte to the Slave. Each time a byte is received on I2C1 (Slave), an RXNE interrupt occurs and byte is stored into an internal buffer until a RESTART condition. And so each time the Slave acknowledge the byte received, DMA transfer the next data from flash memory buffer to I2C2 TXDR register until Transfer completed. Then Master device generate a RESTART condition with Slave address and a read bit condition. When address Slave match code is received on I2C1, an ADDR interrupt occurs. I2C1 IRQ Handler routine is then checking Address Match Code and direction Read. This will allow Slave to enter in transmitter mode and then send a byte when TXIS interrupt occurs. When byte is received on I2C2, an RXNE event occurs and DMA transfer data from RXDR register to an internal buffer until end of transfer. Master auto-generate a NACK and STOP condition to inform the Slave that the transfer is finished.

The STOP condition generate a STOP interrupt and initiate the end of transmission on Slave side. I2C1 IRQ handler and Handle_I2C_Master_TransmitReceive() routine are then clearing the STOP flag in both side.

LED1 is On (500 ms) if data are well sent and the Command Code sent to slave is print as follow depending of IDE : Note that:

When resorting to STM32CubeIDE:

Command Code is displayed on debugger as follows: Window–> Show View–> Console. In Debug configuration :

After each use cases, the LED1 blinks quickly to wait for a new user-button press to send a new Command code to the Slave device.

In all cases, if an error occurs, LED1 is blinking slowly.

Keywords

Connectivity, Communication, I2C, DMA, Interrupt, Master, Slave, Transmission, Reception, Fast mode, command, acknowledgement

Directory contents

Hardware and Software environment

How to use it ?

In order to make the program work, you must do the following :