Synopsis

typedef struct {
  unsigned address;
  const unsigned char *tx;
  size_t txlen;
  unsigned char *rx;
  size_t rxlen;
} CTL_I2C_REQUEST_t;

Description

CTL_I2C_REQUEST_t is an I/O request block for an I2C transaction. Clients are not required to use this request block directly from the I2C API, but I2C drivers are required to implement I/O requests according to the block's members:

• Write-Read request:  If both tx and rx are non-null, the I/O request first writes the slave address and data specified by tx and txlen to the bus, issues a repeated start, and reads rxlen bytes from the bus into rx, and finally issues a stop.
• Write request:  If tx is non-null and rx is null, the I/O request writes the slave address and data specified by tx and txlen to the bus, and then issues a stop.
• Read request:  If tx is null and rx is non-null, the I/O request writes the slave address to the bus, reads rxlen bytes from the bus to rx, and issues a stop.

Structure

address

8-bit address for the I/O request. The low order bit is undefined when passed to the low-level I2C driver, and the I2C driver must correctly set or reset the R/W bit according to the request phase.

tx

A pointer to the data to write to the bus after the slave address is transmitted. If tx is zero, the driver must skip the write part of the I/O request.

txlen

The number of bytes to transfer as payload in the write part of the I/O request.

rx

A pointer to the data to read from the bus after the slave address is transmitted. If rx is zero, the driver must skip the read part of the I/O request.

rxlen

The number of bytes to transfer as payload in the read part of the I/O request.