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AT07334: SAM4 TWI Master Mode Driver [APPLICATION NOTE]

42274A-MCU-05/2014

Note

The read/write functions will enable and disable the corresponding interrupt sources.

8.4 Usage Steps

8.4.1 twim_basic_usage_code

We can send data to the target slave device. Firstly, the data package should be prepared. In one data package,

several items should be set; the target slave address, the internal address (if needed), the length of the internal

address (if needed), the data buffer to be written, and the length of the data buffer.

twi_package_t packet_tx;

packet_tx.chip = TARGET_SLAVE_ADDRESS; // The address of the TWI Slave device.

packet_tx.addr[0] = (INTERNAL_ADDRESS >> 16) & 0xFF;

packet_tx.addr[1] = (INTERNAL_ADDRESS >> 8) & 0xFF;

packet_tx.addr_length = INTERNAL_ADDRESS_LENGTH;

packet_tx.buffer = (void *) data_buf_tx;

packet_tx.length = DATA_BUF_TX_LENGTH;

Note

The TWIM driver supports 1-3 bytes of internal address.

After the data package is ready, we can call twi_master_write() to send the package to the slave address. The

callback set before will be handled in ISR.

twi_master_write(TWIM1, &packet_tx);

Note

If the function returns STATUS_OK, the package has been sent to the target slave device

successfully. Otherwise, the transmission fails.

We can receive data from the target slave device. Firstly, the data package should be prepared. In one data

package, several items should be set; the target slave address, the internal address (if needed), the length of the

internal address (if needed), the data buffer used to store received data and the length of the data to be received.

twi_package_t packet_rx;

packet_rx.chip = TARGET_SLAVE_ADDRESS;

packet_rx.addr[0] = (INTERNAL_ADDRESS >> 16) & 0xFF;

packet_rx.addr[1] = (INTERNAL_ADDRESS >> 8) & 0xFF;

packet_rx.addr_length = INTERNAL_ADDRESS_LENGTH;

packet_rx.buffer = (void *) data_buf_rx;

packet_rx.length = DATA_BUF_RX_LENGTH;

Note

The TWIM driver supports 1-3 bytes of internal address.

Once the data package is ready, we can call twi_master_read() to receive a data package, in responde, from the

slave device. The callback set before will be handled in ISR.

twi_master_read(TWIM1, &packet_rx);

Note

If the function returns STATUS_OK, the package has been received from the target slave device and

the data has been stored in the data buffer successfully. Otherwise, the transmission failed.

Atmel SAM4 Series User Manual

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