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How to read register values from a specific register using fsl_i2c.c driver?

Question asked by O&#39;Driscoll on Mar 22, 2018
Latest reply on Mar 27, 2018 by O&#39;Driscoll

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I m a little confused with this driver. I have previously used I2C to read and write to registers but I m stuck trying to do this with fsl_i2c.c. I have run the sample code from the dev kit, SDK_2.2.1_LPCXpresso54114. This included the code i2c_polling_transfer and i2c_interrupt_transfer. This worked successfully and I was able to send and receive the example byte array through I2C. However I m trying to use these functions with a peripheral to write to a specific register. I m a bit mixed up as to whats defined as a register address and a register value.

For example, if I want to read from the register value of a device at an address such as 0x20. Would I do the following,

#define I2C_MASTER_SLAVE_ADDR_7BIT 0x20

#define I2C_DATA_LENGTH 1U

#define EXAMPLE_I2C_MASTER_BASE (I2C6_BASE)

#define EXAMPLE_I2C_SLAVE_BASE (I2C6_BASE)

#define EXAMPLE_I2C_MASTER ((I2C_Type *)EXAMPLE_I2C_MASTER_BASE)
#define EXAMPLE_I2C_SLAVE ((I2C_Type *)EXAMPLE_I2C_SLAVE_BASE)

g_master_buff[0] = 0x00;

    masterXfer.slaveAddress = I2C_MASTER_SLAVE_ADDR_7BIT;
    masterXfer.direction = kI2C_Write;
    masterXfer.subaddress = 0;
    masterXfer.subaddressSize = 0;
    masterXfer.data = g_master_buff;
    masterXfer.dataSize = I2C_DATA_LENGTH;
    masterXfer.flags = kI2C_TransferDefaultFlag;

reVal = I2C_MasterTransferBlocking(EXAMPLE_I2C_MASTER, &masterXfer);

I just want to read from a device register but I don't know how to define my master buffer, eg g_master_buff[0] = 0x00;.

Can I just run the function,

I2C_MasterReadBlocking(EXAMPLE_I2C_MASTER_BASE, g_test_receive, I2C_DATA_LENGTH, 0);

Or do you just need to use a I2C_MasterWriteBlocking() function and the slave callback function will automatically send back the register values?

Thank you.

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jeremyzhou

Mar 23, 2018 1:42 AM

Hi Ronan O&#39;Driscoll ,

Thank you for your interest in NXP Semiconductor products and

the opportunity to serve you.

I‘d highly recommend you to use the I2C_MasterTransferBlocking() to write or read the external I2C device, such as EEPROM memory device.

Hope it helps.

Have a great day,

TIC

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O&#39;Driscoll @ jeremyzhou on Mar 27, 2018 7:07 AM

I managed to get this working. There was a very useful function I found on some website that helped.

void VEML6075_Init()
{
    BOARD_InitI2C();
   //VEML6075，0x40

    I2C_MasterGetDefaultConfig(&masterConfig); /*******************************************************************************************************/

    masterConfig.baudRate_Bps = I2C_BAUDRATE;
    sourceClock = I2C_MASTER_CLK_FREQ;

    I2C_MasterInit(EXAMPLE_I2C_MASTER_BASEADDR, &masterConfig, sourceClock); /*******************************************************************************************************/

txSize = 3;
rxSize = 0;
txData[0]=0x00;
txData[1]=0x40; // 800ms
txData[3]=0x00; ;

SetupXferRecAndExecute(I2C_ADDR_7BIT, txData,txSize, rxData, rxSize);/*******************************************************************************************************/

txSize = 1;
rxSize = 2;
txData[0]=0x0C;

SetupXferRecAndExecute(I2C_ADDR_7BIT, txData,txSize, rxData, rxSize);/*******************************************************************************************************/
}

static void SetupXferRecAndExecute(uint8_t devAddr,uint8_t *txBuffPtr,uint16_t txSize,uint8_t *rxBuffPtr,uint16_t rxSize)
{
    memset(&masterXfer, 0, sizeof(masterXfer));
    masterXfer.slaveAddress = VEML6075_I2C_ADDR_7BIT;
    masterXfer.direction = kI2C_Write;
    masterXfer.subaddress = 0;
    masterXfer.subaddressSize = 0;
    masterXfer.data = txBuffPtr;
    masterXfer.dataSize = txSize;
    masterXfer.flags = kI2C_TransferNoStopFlag;

    I2C_MasterTransferBlocking(EXAMPLE_I2C_MASTER_BASEADDR, &masterXfer);/*******************************************************************************************************/

    memset(&masterXfer, 0, sizeof(masterXfer));
    masterXfer.slaveAddress = VEML6075_I2C_ADDR_7BIT;
    masterXfer.direction = kI2C_Read;
    masterXfer.subaddress = 0;
    masterXfer.subaddressSize = 0;
    masterXfer.data = rxBuffPtr;
    masterXfer.dataSize = rxSize;
    masterXfer.flags = kI2C_TransferRepeatedStartFlag;

    I2C_MasterTransferBlocking(EXAMPLE_I2C_MASTER_BASEADDR, &masterXfer); /*******************************************************************************************************/
}

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2 Replies

jeremyzhou Mar 23, 2018 1:42 AM
Mark Correct
Correct Answer
Hi Ronan O&#39;Driscoll ,
Thank you for your interest in NXP Semiconductor products and
the opportunity to serve you.
I‘d highly recommend you to use the I2C_MasterTransferBlocking() to write or read the external I2C device, such as EEPROM memory device.
Hope it helps.
Have a great day,
TIC

-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------
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- O&#39;Driscoll @ jeremyzhou on Mar 27, 2018 7:07 AM
  Mark Correct
  Correct Answer
  I managed to get this working. There was a very useful function I found on some website that helped.
  void VEML6075_Init()
  {
      BOARD_InitI2C();
     //VEML6075，0x40
  
      I2C_MasterGetDefaultConfig(&masterConfig); /*******************************************************************************************************/
  
      masterConfig.baudRate_Bps = I2C_BAUDRATE;
      sourceClock = I2C_MASTER_CLK_FREQ;
  
      I2C_MasterInit(EXAMPLE_I2C_MASTER_BASEADDR, &masterConfig, sourceClock); /*******************************************************************************************************/
  
  txSize = 3;
  rxSize = 0;
  txData[0]=0x00;
  txData[1]=0x40; // 800ms
  txData[3]=0x00; ;
  
  SetupXferRecAndExecute(I2C_ADDR_7BIT, txData,txSize, rxData, rxSize);/*******************************************************************************************************/
  
  txSize = 1;
  rxSize = 2;
  txData[0]=0x0C;
  
  SetupXferRecAndExecute(I2C_ADDR_7BIT, txData,txSize, rxData, rxSize);/*******************************************************************************************************/
  }
  static void SetupXferRecAndExecute(uint8_t devAddr,uint8_t *txBuffPtr,uint16_t txSize,uint8_t *rxBuffPtr,uint16_t rxSize)
  {
      memset(&masterXfer, 0, sizeof(masterXfer));
      masterXfer.slaveAddress = VEML6075_I2C_ADDR_7BIT;
      masterXfer.direction = kI2C_Write;
      masterXfer.subaddress = 0;
      masterXfer.subaddressSize = 0;
      masterXfer.data = txBuffPtr;
      masterXfer.dataSize = txSize;
      masterXfer.flags = kI2C_TransferNoStopFlag;
  
      I2C_MasterTransferBlocking(EXAMPLE_I2C_MASTER_BASEADDR, &masterXfer);/*******************************************************************************************************/
  
      memset(&masterXfer, 0, sizeof(masterXfer));
      masterXfer.slaveAddress = VEML6075_I2C_ADDR_7BIT;
      masterXfer.direction = kI2C_Read;
      masterXfer.subaddress = 0;
      masterXfer.subaddressSize = 0;
      masterXfer.data = rxBuffPtr;
      masterXfer.dataSize = rxSize;
      masterXfer.flags = kI2C_TransferRepeatedStartFlag;
  
      I2C_MasterTransferBlocking(EXAMPLE_I2C_MASTER_BASEADDR, &masterXfer); /*******************************************************************************************************/
  }
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How to read register values from a specific register using fsl_i2c.c driver?

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