PI 2 Design CM4AES Hardware Reference Manual

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Pi 2 Design CM4AES Hardware Reference Manual – P0.1
Pi
2
Design
CM4AES
CM4 Digital Audio Carrier
Hardware Reference Manual
© 2021 PI 2 Design
PAGE 1

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Summary of Contents for PI 2 Design CM4AES

  • Page 1 Pi 2 Design CM4AES Hardware Reference Manual – P0.1 Design CM4AES CM4 Digital Audio Carrier Hardware Reference Manual © 2021 PI 2 Design PAGE 1...
  • Page 2: Table Of Contents

    Errata ...................................... 22 List of Figures Figure 1 – CM4AES Block Diagram ..............................6 Figure 2 – CM4AES Power, Simplified Block Diagram ........................13 Figure 3 – CM4AES Power Control Schematic ..........................13 Figure 4 – CM4AES Connector Locations ............................16...
  • Page 3: Warranty

    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,...
  • Page 4: Operating Specifications

    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...
  • Page 5: Overview

    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.
  • Page 6: Figure 1 - Cm4Aes Block Diagram

    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...
  • Page 7: On-Board Devices

    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.
  • Page 8: Wm8804 Spdif Transmitter

    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.
  • Page 9: I2S Parallel Buffer

    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.
  • Page 10: Cm4 Ports And Gpio

    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.
  • Page 11: Compute Module 4 Gpio

    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.
  • Page 12: Cm4 Gpio Notes

    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...
  • Page 13: Cm4Aes Power

    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.
  • Page 14: Power Status

    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).
  • Page 15: Cm4Aes Software

    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.
  • Page 16: Connector Locations

    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...
  • Page 17: P1 - Expansion I/O Connector

    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...
  • Page 18: P3 - Console Uart, Factory Use Only

    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.
  • Page 19: P13 - Expansion Power Connector

    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...
  • Page 20: U15 - Combo Rca/Opto Transmitter

    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-...
  • Page 21: Document Revisions

    Pi 2 Design CM4AES Hardware Reference Manual – P0.1 9 DOCUMENT REVISIONS Date Revision Change 10/09/2021 P0.1 Preliminary Release Table 9 – Document Revisions PAGE 21...
  • Page 22: Errata

    Pi 2 Design CM4AES Hardware Reference Manual – P0.1 10 ERRATA 10.1 OVERVIEW There are currently no known errata for the CM4AES Rev. P6. PAGE 22...

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