Overview

The I²C driver in the CYGPKG_DEVS_I2C_DWI2C supports the use of I²C devices within eCos. Access to the driver will be via the standard I²C interface subsystem.

This driver provides support for all four I²C busses available on the HPS. The number of interfaces supported is defined by the platform HAL.

Configuration

The HAL contains the following configuration options for each the I²C busses:

Usage Notes

The design of the I²C device does not make it possible to start a new bus transfer without also sending a START condition on the bus. This means that divided transactions are not possible. A divided transaction would look like this:

    cyg_i2c_transaction_begin(&cyg_aardvark_at24c02);
    cyg_i2c_transaction_tx(&cyg_aardvark_at24c02, 1, tx_buf1, 1, 0);
    cyg_i2c_transaction_tx(&cyg_aardvark_at24c02, 0, tx_buf2, 2, 0);
    cyg_i2c_transaction_tx(&cyg_aardvark_at24c02, 0, tx_buf3, 6, 1);
    cyg_i2c_transaction_end(&cyg_aardvark_at24c02);

In this transaction a START and one byte are sent from tx_buf1, then 2 bytes of data from tx_buf2, finishing with 6 bytes from tx_buf3 followed by a STOP. The device will not allow the tx_buf2 and tx_buf3 transfers to happen without also sending a START. The only solution to this is to combine the data into a single buffer and perform a single transfer:

    memcpy( tx_buf, tx_buf1, 1);
    memcpy( tx_buf+1, tx_buf2, 2);
    memcpy( tx_buf+3, tx_buf3, 6);
    cyg_i2c_tx(&cyg_aardvark_at24c02, tx_buf, 9);