ARM® Cortex® M4 Cookbook

Configuring the audio codec

The STM32F400 evaluation board schematic (http://www.keil.com) shows that a Cirrus Logic CS42L52 codec IC (http://www.cirrus.com) is used, and the I2S bus signals are driven by GPIO port I bits 0, 1, and 3. SDIN and SDOUT are wired together, so the I2S interface must be operated half-duplex. In addition to managing the I2S interface, the microcontroller must also source a Master Clock (MCLK), which clocks the codec's delta-sigma modulators (Note that we described a function to achieve this in Chapter 6, Multimedia Support). A block diagram that summarizes the I2S interface connection is shown, as follows:

The codec also ...