PM0222 datasheet(26/33 Pages) STMICROELECTRONICS

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I2C

PM0222

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10.3

I2C configuration

Following a reset, the I²C logic is disabled and must be configured when in this state.

The control register (I2C_CR) and baud rate register (I2C_BRCR) need to be programmed

to configure the following parameters of the peripheral:



Master or slave



7- or 10-bit addressing mode



Speed mode



Clock rate

Note:

If in slave mode, the I2C_SCR register has to be programmed with the selected slave

address.

Then if in master mode, the I2C_MCR register is used to define the transaction:



Read or write



Slave addresses (7- or 10-bit) to communicate with



Addressing a 7- or 10-bit slave address



Stop condition, to generate a stop or restart condition at the end of the transaction (for

consecutive transactions)



Transaction length

Note:

For a master write, the data to transmit have to be written to the transmit FIFO in the

I2C_TFR register. For a master read, when the master transaction is done, data are

available in the receive FIFO in I2C_RFR.

Before using these examples the I²C module has to be enabled on the CRMU (see

Section 3.1: Peripheral clock gating) and the correct mode has to be configured for the

corresponding IO (see Section 5.1.1: I/O mode).

10.3.1

I2C master

This section will show an example as follows:



Configure the I2C2 IP in master mode with 300 kHz in fast mode



Launch a master write operation of one 8-bit data (0x18), to a slave addressed at 0x1D,

in 7-bit addressing mode

// define the I²C clock rate

// (see calculation in Section 10.2: I2C clock rate calculation example).

I2C2->I2C_BRCR = 0x1D

// enable the peripheral; select the master mode and the fast mode for the baud

// rate generation

I2C2->I2C_CR = 0x01 + (0x1<<1) + (0x1<<4)

Once the I²C peripheral is correctly initiated, the I2C_MCR register has to be configured to

begin a transaction.

// write operation, slave address, 7-bit addressing mode, stop condition generated,

// transaction length

I2C2->I2C_MCR = (0x0) + (0x1D<<1) + (0x1<<12) + (0x1<<14) + (0x1<<15)

I2C2->I2C_TFR = 0x18; // load the data to send in transmit FIFO

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