This warranty is valid only for so long as the product is used intact as shipped from PI 2 Design. Any attempt or effort to alter the Product, including but not limited to any attempt to solder, de-solder, unplug, replace,...
Pi 2 Design CM4AES Hardware Reference Manual – P0.1 2 OPERATING SPECIFICATIONS 2.1 CM4AES OPERATING SPECIFICATIONS The CM4AES conforms to the following specifications: Specification Value Dimensions 170mm x 120mm Weight ~10g Storage Temperature -20C to +85C Operating Temperature 0C to +70C...
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.
Pi 2 Design CM4AES Hardware Reference Manual – P0.1 Refer to the following figure for a block diagram of the CM4AES. 5V @ 5A USB-A USB-A Switching Supply HOST HOST 2.5MM USB-A USB-A DC Jack HOST HOST AP1155 AP1155 10/100 RJ45...
CM4AES. 4.2 COMPUTE MODULE 4 At the core of the CM4AES is the latest Raspberry Pi Compute Module 4. Designed for low-power embedded applications, this module runs the software required to perform the Digital Audio Player function as well as other applications.
Pi 2 Design CM4AES Hardware Reference Manual – P0.1 4.4 WM8804 SPDIF TRANSMITTER At the core of the CM4AES is the Cirrus Logic WM8804 AES Digital Audio Transmitter. This device interfaces to the Compute Module 4 via I2S and I2C. The signals used to interface with the WM8804 are shown in the following table.
Pi 2 Design CM4AES Hardware Reference Manual – P0.1 sends it as a balanced pair to the 1:1 Isolation Transformer and then to the XLR connector. 4.7 I2S PARALLEL BUFFER A 4-Bit Buffer is used to drive the I2S signals (MCLK, BCKL, LRCLK and SDO) to the I2S Expansion Flex Connector.
Pi 2 Design CM4AES Hardware Reference Manual – P0.1 5 CM4 PORTS AND GPIO 5.1 OVERVIEW The CM4AES uses a number of the Interface Ports and GPIO from the CM4 for control and status purposes. 5.2 COMPUTE MODULE 4 PORTS Certain CM4 Port pins are hardwired and are always available when enabled.
The CM4 provides a large number of General Purpose I/O (GPIO) pins. These pins also can be assigned to alternate functions as defined in the CM4 documentation. The usage of these pins (and alternate functions) on the CM4AES are described in the following table.
Pi 2 Design CM4AES Hardware Reference Manual – P0.1 GPIO CM4AES Description/Notes Usage SDOUT I2S Serial Data to WM8804 PHLD Power Hold to Power Circuit *ROT_SW Rotary Center Switch, Routed to P17 *PSW Power On Switch from Power Circuit ROT_CK...
Figure 2 – CM4AES Power, Simplified Block Diagram 6.2 POWER CONTROL This circuit allows software to monitor and control the power state of the CM4AES. It uses two GPIO to perform the Power Hold and Power State functions. This circuit is compatible with the Volumio 503HTA Plug-In.
Pi 2 Design CM4AES Hardware Reference Manual – P0.1 6.3 POWER STATUS As part of the power control circuit, GPIO24 (*PSW) is used to sense the state of the Pushbutton Power Switch. A low indicates that the Power Switch is in the on position (depressed).
7 CM4AES SOFTWARE 7.1 OVERVIEW Due to the various resources interfaced on the CM4AES, both internal and external to the CM4, it is necessary to initialize a large number of CPU registers and external devices before correct operation can begin. These values and their proper sequencing are beyond the scope of this document.
Pi 2 Design CM4AES Hardware Reference Manual – P0.1 8 CONNECTOR LOCATIONS 9.1 OVERVIEW This section provides the type, location, and pinout for the various connectors on the CM4AES. HDMI 0 COAX BALANCED AES ETHERNET SD-CARD OPTO DUAL USB HDMI 1 M.2 2282...
Pi 2 Design CM4AES Hardware Reference Manual – P0.1 9.2 P1 – EXPANSION I/O CONNECTOR P1 is an Amphenol HLW20S-2C7LF 20-Pin 1MM Pitch Flex connector. The Pinout for P1 is shown in the following table. P1 PIN Name Description MCLK...
Pi 2 Design CM4AES Hardware Reference Manual – P0.1 9.4 P3 – CONSOLE UART, FACTORY USE ONLY P3 is a 3x1 2.54mm pitch, single row connector It is connected to CM4 UART 1. Pinout is: Pin1 - TXD (GPIO14); Pin 2 – RXD (GPIO15); and Pin 3 – GND. Note these are TTL level and have no ESD protection.
Pi 2 Design CM4AES Hardware Reference Manual – P0.1 9.14 P13 – EXPANSION POWER CONNECTOR P13 is an Amphenol HLW16S-2C7LF 16-Pin 1MM Pitch Flex connector. The Pinout for P13 is shown in the following table. P1 PIN Name Description Ground VCC3 +3.3V from On-Board Switching Supply...
Pi 2 Design CM4AES Hardware Reference Manual – P0.1 P15 PIN Name Description SDO+ I2S Data Plus Ground SDO- I2S Data Minus BCK+ I2S Bit Clock Plus Ground BCK- I2S Bit Clock Minus LRCLK+ I2S Left/Right Clock Plus Ground LRCLK-...
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