The following example shows how to configure the
I2C module to transmit a single byte as a master. This assumes the
system clock is 200 MHz.
- Enable the I2C clock using the CMPCLKCR0 register
in the system control module.
- In the GPIO module, configure GPxCSELy register
to allow CM core to control corresponding GPIOs. To determine which GPIOs to
configure, see the GPIO Muxed Pins tables in the device data sheet.
- Configure GPxGMUXy and GPxMUXy register to assign
the I2C signals to the appropriate pins.
Note: The GPIO configuration
register GPyODR must be set to normal mode when the CM-I2C is used. The
open-drain operation for CM-I2C is managed by the CM-I2C module.
- Initialize the I2C master by writing the
I2CMCS_WRITE register with a value of 0x0000.0010.
- Set the desired SCL clock speed of 100 kbps by
writing the I2CMTPR register with the correct value. The value written to the
I2CMTPR register represents the number of system clock periods in one SCL clock
period. The TPR value is calculated by:
TPR = (System Clock / (2 × (SCL_LP + SCL_HP) ×
SCL_CLK)) – 1
TPR = (200 MHz / (2 × (6 + 4) × 100000)) –
1
TPR
= 99 (or) 0x63
Write the I2CMTPR register
with the value of 0x0000.0063.
- Specify the slave address of the
master and that the
next operation is a Transmit by writing the I2CMSA register with a value of
0x0000.0076. This sets the slave
address to 0x3B.
- Place data (byte) to be transmitted in the data register by writing the I2CMDR register with the desired data.
- Initiate a single byte transmit of the data from
the master to the slave by writing the
I2CMCS register with a value of 0x0000.0007 (STOP, START, RUN).
- Wait until the transmission completes by polling the BUSBSY bit in the I2CMCS register until it has been cleared.
- Check the ERROR bit in the I2CMCS register to confirm the transmit was acknowledged.