LoopBack

This sample demonstrates using I2C for self-transmitting and self-receiving communication.

I2C0 acts as the master and reads data length and information transmitted by I2C1, while I2C1 acts as the slave and receives data length and information sent by I2C0, thereby implementing I2C communication functionality.

Requirements

The sample supports the following development kits:

Development Kits

Hardware Platforms

Board Name

RTL87x2G HDK

RTL87x2G EVB

For more requirements, please refer to Quick Start.

Wiring

Connect P4_0(I2C0 SCL) to P4_2(I2C1 SCL), P4_1(I2C0 SDA) to P4_3(I2C1 SDA) on the EVB, need to connect 2.2k pull-up resistor.

The connection schematic of the pull-up resistor is shown below:

Here should be the I2C pull-up resistor schematic

I2C pull-up resistor schematic

Configurations

The example configurable macros are as follows:

  1. I2C_MASTER_SEND_SLAVE_RECEIVE : Enable this macro to configure the example as a master sends and a slave receives.

  2. I2C_MASTER_RECEIVE_SLAVE_SEND : Enable this macro to configure the example as a master receives and a slave sends.

  3. I2C_MASTER_REPEAT_READ : Enable this macro to configure the example for the master to continuously send and receive data.

Building and Downloading

This sample can be found in the SDK folder:

Project file: samples\peripheral\i2c\trx_loopback\proj\rtl87x2g\mdk

Project file: samples\peripheral\i2c\trx_loopback\proj\rtl87x2g\gcc

To build and run the sample, follow the steps listed below:

  1. Open sample project file.

  2. To build the target, follow the steps listed on the Generating App Image in Quick Start.

  3. After a successful compilation, the app bin app_MP_xxx.bin will be generated in the directory mdk\bin or gcc\bin.

  4. To download app bin into EVB board, follow the steps listed on the MP Tool Download in Quick Start.

  5. Press reset button on EVB board and it will start running.

Experimental Verification

When enabling I2C master send slave receive I2C_MASTER_SEND_SLAVE_RECEIVE :

  1. When the data received at the SLAVE side reaches the set threshold level, trigger the I2C_INT_RX_FULL interrupt and print log.

    I2C1 Rx Full detected

  2. When the MASTER finishes sending data and the SLAVE detects the stop signal, the MASTER and SLAVE trigger the I2C_INT_STOP_DET interrupt and print log.

    I2C0 Stop signal detected
I2C1 Stop signal detected

  3. Within the SLAVE interrupt function, the SLAVE prints the length and content of the data received.

    Slave Recv Date Lenth = 24
I2C1_Slave_ReceiveData=0
...
I2C1_Slave_ReceiveData=23

When enabling I2C master to receive slave send I2C_MASTER_RECEIVE_SLAVE_SEND :

  1. The SLAVE receives the read request from the MASTER, the SLAVE triggers I2C_INT_RD_REQ interrupt and prints log.

    Enter I2C1 interrupt I2C1_INT_RD_REQ!

  2. Print the data received at the MASTER.

    Master Read data = 10
...
Master Read data = 33

When enabling I2C master repeat read I2C_MASTER_REPEAT_READ :

  1. The SLAVE receives the read request from the MASTER, the SLAVE triggers I2C_INT_RD_REQ interrupt and prints log.

    Enter I2C1 interrupt I2C1_INT_RD_REQ!

  2. The SLAVE receives the data from the MASTER and prints the length and values of the received data in the SLAVE ISR.

    Slave Recv Date Lenth = 4
I2C1_Slave_ReceiveData=1
I2C1_Slave_ReceiveData=2
I2C1_Slave_ReceiveData=3
I2C1_Slave_ReceiveData=4

  3. The SLAVE finishes receiving data and prints log.

    I2C1 RX_DONE detected

  4. The SLAVE sends data back to the MASTER, and after the MASTER finishes receiving the data, it prints log.

    I2C0 Stop signal detected

  5. Print the data received by the MASTER side.

    Master Repeat Read data = 10
...
Master Repeat Read data = 33

Code Overview

This chapter will be introduced according to the following several parts:

  1. Source Code Directory.

  2. Peripheral initialization will be introduced in chapter Initialization .

  3. Functional implementation after initialization will be introduced in chapter Functional Implementation .

Source Code Directory

  • Project Directory: sdk\samples\peripheral\i2c\trx_loopback\proj

  • Source Code Directory: sdk\samples\peripheral\i2c\trx_loopback\src

Source files are currently categorized into several groups as below.

└── Project: trx_loopback
    └── secure_only_app
        └── Device                   includes startup code
            ├── startup_rtl.c
            └── system_rtl.c
        ├── CMSIS                    includes CMSIS header files
        ├── CMSE Library             Non-secure callable lib
        ├── Lib                      includes all binary symbol files that user application is built on
            └── rtl87x2g_io.lib
        ├── Peripheral               includes all peripheral drivers and module code used by the application
            ├── rtl_rcc.c
            ├── rtl_pinmux.c
            ├── rtl_nvic.c
            ├── rtl_gdma.c
            └── rtl_i2c.c
        └── APP                      includes the ble_peripheral user application implementation
            ├── main_ns.c
            └── io_i2c.c

Initialization

The initialization process includes board_i2c_master_init, board_i2c_slave_init, driver_i2c_master_init, driver_i2c_slave_init and nvic_i2c_config.

board_i2c_master_init and board_i2c_slave_init contain the PAD and PINMUX settings for I2C0 and I2C1:

  1. Config PAD: Set pins as PINMUX mode, PowerOn, internal Pull-Up.

  2. Config PINMUX: Assign pins for I2C0_CLK, I2C0_DAT, I2C1_CLK, I2C1_DAT functions respectively.

driver_i2c_master_init contains the initialization of the I2C0 peripheral:

  1. Enable PCC clock.

  2. Set the I2C clock frequency to 100k.

  3. Set the device mode to master mode.

  4. Set the I2C address to 7-bit address mode.

  5. Set the slave address bit to 0x50.

  6. Enable the ACK function.

  7. Enable I2C0.

RCC_PeriphClockCmd(APBPeriph_I2C0, APBPeriph_I2C0_CLOCK, ENABLE);
...
I2C_InitStruct.I2C_ClockSpeed       = 100000;
I2C_InitStruct.I2C_DeviveMode       = I2C_DeviveMode_Master;
I2C_InitStruct.I2C_AddressMode      = I2C_AddressMode_7BIT;
I2C_InitStruct.I2C_SlaveAddress     = 0x50;
I2C_InitStruct.I2C_RxThresholdLevel = 8;
I2C_InitStruct.I2C_Ack              = ENABLE;

driver_i2c_slave_init contains the initialization of I2C1 peripherals:

  1. Enable PCC clock.

  2. Set the I2C clock frequency to 100k.

  3. Set the device mode to slave mode.

  4. Set the I2C address to 7-bit address mode.

  5. Set slave address bit 0x50.

  6. Enable the ACK function.

  7. Enable I2C1.

RCC_PeriphClockCmd(APBPeriph_I2C1, APBPeriph_I2C1_CLOCK, ENABLE);
...
I2C_InitStruct.I2C_ClockSpeed       = 100000;
I2C_InitStruct.I2C_DeviveMode       = I2C_DeviveMode_Slave;
I2C_InitStruct.I2C_AddressMode      = I2C_AddressMode_7BIT;
I2C_InitStruct.I2C_SlaveAddress     = 0x50;
I2C_InitStruct.I2C_RxThresholdLevel = 8;
I2C_InitStruct.I2C_Ack              = ENABLE;

nvic_i2c_config contains the initialization of interrupts:

  1. Clear the interrupt pending bit.

  2. Enable I2C0 and I2C1 interrupts according to the specific transmit or receive settings in the program.

  I2C_ClearINTPendingBit(I2C0, I2C_INT_STOP_DET);
  ...

#if I2C_MASTER_SEND_SLAVE_RECEIVE
  I2C_INTConfig(I2C0, I2C_INT_STOP_DET, ENABLE);
  I2C_INTConfig(I2C1, I2C_INT_RX_FULL, ENABLE);
  I2C_INTConfig(I2C1,  I2C_INT_STOP_DET, ENABLE);
  I2C_INTConfig(I2C1,  I2C_INT_RX_DONE, ENABLE);
#endif

#if I2C_MASTER_RECEIVE_SLAVE_SEND
  I2C_INTConfig(I2C1, I2C_INT_RD_REQ, ENABLE);
#endif

#if I2C_MASTER_REPEAT_READ
  I2C_INTConfig(I2C0, I2C_INT_STOP_DET, ENABLE);
  I2C_INTConfig(I2C1, I2C_INT_RX_FULL, ENABLE);
  I2C_INTConfig(I2C1,  I2C_INT_STOP_DET, ENABLE);
  I2C_INTConfig(I2C1,  I2C_INT_RX_DONE, ENABLE);
  I2C_INTConfig(I2C1, I2C_INT_RD_REQ, ENABLE);
#endif
...

Functional Implementation

When enabling I2C master send slave receive I2C_MASTER_SEND_SLAVE_RECEIVE :

  1. Execute I2C_MasterWrite() and the master sends the data in the write_data array to the slave.

  2. The slave receives the data sent by the master, and when the slave reaches the threshold, it triggers the I2C_INT_RX_FULL or detects the stop signal, it triggers the I2C_INT_STOP_DET interrupt, and enters the interrupt handler function :cpp:any:I2C1_Handler.

  3. Determine when the receive full state is detected as SET:

    1. Get the length of the received data in the RX FIFO and save the received data.

    2. Clear the I2C_INT_RX_FULL interrupt pending bit.

  4. When the slave detects the stop signal status as SET:

    1. Obtain the length of the received data in the RX FIFO and save the received data.

    2. Print the total length of the received data and the received data information.

    3. Clear the I2C_INT_STOP_DET interrupt pending bit.

if (I2C_GetINTStatus(I2C1, I2C_INT_STOP_DET) == SET)
{
   DBG_DIRECT("I2C1 Stop signal detected");

   /*read I2C receive data*/
   lenth = I2C_GetRxFIFOLen(I2C1);
   for (uint32_t i = 0; i < lenth; i++)
   {

      I2C_Rev_Data[I2C_Rev_Index++] = I2C_ReceiveData(I2C1);
   }
   I2C_Rev_Data_Lenth += lenth;
   I2C_ClearINTPendingBit(I2C1, I2C_INT_STOP_DET);
   ...
}
...
if (I2C_GetINTStatus(I2C1, I2C_INT_RX_FULL) == SET)
{
   DBG_DIRECT("I2C1 Rx Full detected");
   lenth = I2C_GetRxFIFOLen(I2C1);

   /*read I2C data*/
   for (uint32_t i = 0; i < lenth; i++)
   {
      I2C_Rev_Data[I2C_Rev_Index++] = I2C_ReceiveData(I2C1);
   }
   I2C_Rev_Data_Lenth += lenth;

   I2C_ClearINTPendingBit(I2C1, I2C_INT_RX_FULL);
}

When enable I2C master receive slave send I2C_MASTER_RECEIVE_SLAVE_SEND :

  1. Execute I2C_MasterRead() , the master sends master read command to the slave.

  2. The slave detects the RD_REQ request and triggers the I2C_INT_RD_REQ interrupt, and enters the interrupt handler function I2C1_Handler.

    1. Execute I2C_SendCmd() command to send data to the host.

    2. Clear the I2C_INT_RD_REQ interrupt pending bit after sending data.

for (uint32_t i = 0; i < TransferLength; i++)
{
   I2C_SendCmd(I2C1, I2C_WRITE_CMD, send_data_buffer[i], DISABLE);
}

I2C_ClearINTPendingBit(I2C1, I2C_INT_RD_REQ);

  1. Print the data received by the master.

When enabling I2C master repeat read I2C_MASTER_REPEAT_READ :

  1. Execute I2C_RepeatRead(), the master sends the repeat read command to the slave, sends the data in tx_data, and receives the data stored in rx_data.

uint8_t tx_data[10] = {01, 02, 03, 04};
uint8_t rx_data[TransferLength] = {0};
I2C_RepeatRead(I2C0, tx_data, 4, rx_data, TransferLength);

  1. The slave receives the data sent by the host and triggers the I2C_INT_RX_FULL interrupt when the slave receives a full FIFO, or triggers the I2C_INT_STOP_DET interrupt when it detects a stop signal. The I2C_INT_RD_REQ interrupt is triggered when the slave detects the RD_REQ application and enters the interrupt handler function I2C1_Handler (same as above)