Pi 2 Design CM4AES Hardware Reference Manual – P0.1
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3
OVERVIEW
3.1
INTRODUCTION
The CM4AES, designed and manufactured by PI 2 Design, is a Compute Module 4
Carrier Board designed for Professional, Studio Grade, Digital Audio Streaming. The
CM4AES converts the Compute Module 4 I2S Interface to High Definition Digital Audio
Coax, OPTO and Balanced XLR. These multiple, simultaneously active digital audio
outputs allow the CM4AES to optimally interface with virtually any High Performance
DAC on the market.
The major features of the CM4AES are as follows:
•
COMPUTE MODULE 4 -
This latest module from the Raspberry Pi Foundation provides 4 High
Performance ARM Cores, Dual 4K HDMI Output, PCIe x1, Gigabit Ethernet
and more.
•
M.2 2282 SSD -
A Standard M.2 Socket is provided for nVME Storage via the CM4 PCI Express x1
Link. The socket supports both “M” Key and “B” Key devices.
•
GIGABIT ETHERNET -
A standard RJ45 Provides the interface to the CM4 Gigabit Ethernet I/F.
•
DUAL EXTERNAL USB2.0 -
This connector provides two USB2.0 Host Ports for mass storage, USB
Peripherals, DAC Interface, etc.
•
INTERNAL USB -
A vertical USB2.0 Connector is provided to interface with LCD Touch Screens in
an Internal LCD system.
•
EXTERNAL HDMI -
One 4K HDMI Connector allows access to CM4 HDMI Output 0.
•
INTERNAL HDMI -
A vertical HDMI connector allows access to CM4 HDMI Output 1.
•
AES TRANSMITTER –
The industry standard WM8804 converts the CM4 I2S stream to AES3/SPDIF
formatted data at 24-Bit up to 192Khz Frame Rate
•
COAX OUTPUT –
A 1:1 Isolation Transformer provides Bit Perfect Impedance Controlled Coaxial
Transmission of the Digital Audio Data
•
SPDIF OPTICAL OUTPUT –
Isolated Optical Transmitter Drives Consumer Level DAC’s
•
BALANCED OUTPUT
– An RS-485 Transmitter coupled with a 1:1 Isolation Transformer allows
the transmission of balanced audio data via the Professional Audio Standard XLR Connector
•
BUFFERED I2S OUTPUT –
Parallel Buffered I2S is available for direct short distance connection to
off-board D/A. Perfect for DIY use! I2C for control is also provided as well as 5V Regulated and Input
Voltage Rails.
•
DIFFERENTIAL I2S OUTPUT –
An LVDS Differential Transmitters is used to drive the I2S Bus over
a standard HDMI Connector. The Pinout conforms to the PS Audio Standard.
•
HIGH RESOLUTION CLOCKS –
A pair of Ultra-Low Noise NDK NZ2520SDA oscillators allow the
WM8804 to operate in non-PLL mode for the lowest possible noise.
•
ULTRA-LOW NOISE LDO’s –
Separate Ultra-Low Noise LT3042 LDO’s (0.9 uV noise and 80 dB
PSRR) are used to supply the WM8804 Transmit Section and the NDK Clock’s.
•
LOW NOISE PCB LAYOUT
– Constructed with 4-layer Split Ground PCB with noise reduction
techniques refined from years of High-Speed Mixed-Signal Design work
3.2
BLOCK DIAGRAM
