PI2Media PI2AES Hardware Reference Manual – P0.1 - 3/27/2019
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BOARD DEVICES
4.1 OVERVIEW
The PI2AES interfaces to the RPi via the 40-Pin GPIO Connector. This section
describes in detail the devices located on the PI2AES.
4.1 PI2AES I2C BUS DEVICES
The following table describes the CPU I2C Bus usage of the PI2AES. Most of these
addresses are set by the startup script supplied by Pi2Design. Refer to the respective
device documentation for more detail.
I2C
Bus
7-Bit I2C
Address
Description
I2C 0x3B WM8804 SPDIF Transmitter
Table 2 – PI2AES I2C Bus Devices
4.1 WM8804 SPDIF TRANSMITTER
At the core of the PI2AES is the Cirrus Logic WM8804 AES Digital Audio Transmitter.
This device interfaces to the Raspberry Pi via I2S and I2C. The signals used to interface
with the WM8804 are shown in the following table.
WM8804
Signal
RPi
Signal
Description
MCLK - Unused
BCLK BCLK I2S Bit Clock Output to Pi
LRCLK LRCLK I2S Word Clock Output to Pi
SDIN SDOUT I2S Serial Audio Data Input from Pi
SCL SCL I2C Clock from Pi
SDA SDA I2C Data to/from Pi
XIN GPIO5 1 = Select 22.5792Mhz Input Clock for 44.1Khz,
88.2Khz and 176.4Khz Frame Rates
XIN GPIO6 1 = Select 24.576Mhz Input Clock for 48Khz,
96Khz and 192Khz Frame Rates
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