PI 2 Design MERCURY V2 Quick user guide

Pi 2 Design Mercury V2, Hardware Reference Manual – P1
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Pi 2 Design
MERCURY V2
Hardware Reference Manual
© 2022 PI 2 Design

Pi 2 Design Mercury V2, Hardware Reference Manual – P1
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Table of Contents
1 Warranty......................................................................................................................................................................................... 3
2 Operating Specifications ................................................................................................................................................................. 4
2.1 MERCURY V2 Operating specifications .................................................................................................................................. 4
3 Overview ........................................................................................................................................................................................ 5
3.1 Introduction ............................................................................................................................................................................. 5
3.2 Block Diagram......................................................................................................................................................................... 5
4 On-Board Devices .......................................................................................................................................................................... 7
4.1 Overview ................................................................................................................................................................................. 7
4.2 Compute Module 4........................................................................................................................................................... 7
4.2 USB2504A usb hub.......................................................................................................................................................... 7
4.3 WM8804 SPDIF Transmitter ............................................................................................................................................ 8
4.3.1 WM8804 SPDIF Transmitter Notes.............................................................................................................................. 8
4.4 Dual High Resolution NDK Clocks.................................................................................................................................... 8
4.5 RS-485 Differential Transmitter ........................................................................................................................................ 8
4.6 I2S Parallel Buffer ............................................................................................................................................................ 9
4.7 I2S Differential Driver ....................................................................................................................................................... 9
4.8 Audio Data Rate LED’s ..................................................................................................... Error! Bookmark not defined.
5 CM4 Ports and GPIO.............................................................................................................................................................. 10
5.1 Overview........................................................................................................................................................................ 10
5.2 Compute Module 4 Ports................................................................................................................................................ 10
5.2.1 CM4 Port Notes ......................................................................................................................................................... 10
5.3 Compute Module 4 GPIO............................................................................................................................................... 10
5.3.1 CM4 GPIO Notes....................................................................................................................................................... 12
6 MERCURY V2 Power ............................................................................................................................................................. 13
6.1 Overview........................................................................................................................................................................ 13
7 MERCURY V2 Software ......................................................................................................................................................... 15
8 Connector Locations............................................................................................................................................................... 16
8.1 Overview........................................................................................................................................................................ 16
8.2 Front and Rear PaneL and Interior Views....................................................................................................................... 16
8.3 Dual USB ....................................................................................................................................................................... 16
8.4 HDMI 0 and 1................................................................................................................................................................. 17
5.15 Micro-SD Card ............................................................................................................................................................... 17
8.5 Gigabit Ethernet ............................................................................................................................................................. 17
5.16 I2S Over HDMI............................................................................................................................................................... 17
8.6 DIP Switch ..................................................................................................................................................................... 18
8.7 DC Input Jack ................................................................................................................................................................ 18
5.17 TOSLINK OPTO ............................................................................................................................................................ 18
5.18 RCA SPDIF.................................................................................................................................................................... 18
8.8 XLR AES Balanced........................................................................................................................................................ 18
8.9 BNC AES Single Ended ................................................................................................................................................. 18
8.10 Parallel I2s over RJ45 .................................................................................................................................................... 18
10 Document Revisions ............................................................................................................................................................... 20
11 Errata...................................................................................................................................................................................... 21
11.15 Overview ................................................................................................................................................................... 21
List of Figures
Figure 1 – MERCURY V2 Block Diagram .......................................................................................................................................... 6
Figure 2 – MERCURY V2 Power, Simplified Block Diagram ............................................................................................................ 13
Figure 3 – MERCURY V2 Power Control Schematic........................................................................................................................ 13
Figure 4 – MERCURY V2 Front Panel ............................................................................................................................................. 16
Figure 5 – MERCURY V2 Rear Panel.............................................................................................................................................. 16

Pi 2 Design Mercury V2, Hardware Reference Manual – P1
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1WARRANTY
The enclosed product ("the Product") is warranted by Pi 2 Design for a period of one
year for reasonable, individual home use, all as further described and defined below.
This warranty runs solely to the individual purchasing the Product and is not
transferable or assignable in any respect. 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,
add or affix any part or component of or onto the Product, other than components
specifically intended for the user to plug and unplug into appropriate sockets and/or
Connectors to facilitate intended use and deployment, all as specifically described and
authorized in this Product Hardware Reference Manual, shall void this warranty in all
respects. Coverage under this warranty requires that the Product be used and stored at
all times in conditions with proper electrostatic protection necessary and appropriate for
a complex electronic device. These conditions include proper temperature, humidity,
radiation, atmosphere and voltage (standard commercial environment, 0C to +70C,
<60%RH). Any Product that has been modified without the express, prior written
consent of Pi 2 Design is not covered by this warranty. The use or connection of any
adapter or component with any device other than a Pi 2 Design Connector or adapter
shall void this warranty and the warranty of all other components, parts and modules
connected to the rest of the system. Pi 2 Design shall not be responsible for any
damage to the Product as a result of a customer's use or application of circuitry not
developed or approved by Pi 2 Design for use on or in connection with the Product.
This warranty does not cover defects caused by electrical or temperature fluctuations or
from stress resulting from or caused by abuse, misuse or misapplication of the Product.
Any evidence of tampering with the serial number on the Product shall immediately void
this warranty. Notwithstanding anything to the contrary herein, Pi 2 Design expressly
disclaims any implied warranty of merchantability or implied warranty of fitness for a
particular purpose in connection with the manufacture or use of the Product.

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2OPERATING SPECIFICATIONS
2.1 MERCURY V2 OPERATING SPECIFICATIONS
MERCURY V2 conforms to the following specifications:
Specification Value
Dimensions 170mm x 123.2mm x 53.5mm (6.7” x 4.85” x 2.1”)
Weight ~1.2kg (3 lbs.)
Storage Temperature -20C to +85C (-4F to 185F)
Operating Temperature 0C to +70C (32F to 158F)
Humidity 0% to 95% RH, Non-Condensing
Input Voltage (VIN) +12V +/- 20% DC
Power Consumption 5W Typical, 12W Maximum (not including SSD or USB)
Table 1 – MERCURY V2 Operating Specifications

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3OVERVIEW
3.1 INTRODUCTION
MERCURY V2 , designed and manufactured by PI 2 Design, is a Compute Module 4
based device designed for Professional, Studio Grade, Digital Audio Streaming.
MERCURY V2 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 MERCURY V2 to optimally interface with virtually any High-
Performance DAC on the market.
The major features of MERCURY V2 are as follows:
•COMPUTE MODULE 4 - This module provides 4 High Performance ARM Cores, Dual 4K HDMI
Output, PCIe x1, Gigabit Ethernet, 4/8GB DRAM and more.
•M.2 2280 SSD - A Standard M.2 Socket is provided for nVME Storage via the CM4 PCI Express x1
Link. The socket supports both “M” 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.
•EXTERNAL HDMI – Two 4K HDMI Connector allows access to CM4 HDMI Outputs 0 and 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
•AES COAX OUTPUT – A 1:1 Isolation Transformer provides Bit Perfect Impedance Controlled Digital
Audio Data @ 1V AES Standard Level.
•AES BALANCED OUTPUT – An RS-485 Transmitter with a 1:1 Isolation Transformer provides
balanced audio data via the Professional XLR Connector
•TOSLINK OPTICAL OUTPUT – Isolated Optical Transmitter Drives Consumer Level DAC’s
•SPDIF COAX OUPUT - A 1:1 Isolation Transformer provides Bit Perfect Impedance Controlled Digital
Audio Data @ 0.6V Consumer Standard Level.
•DIFFERENTIAL I2S OUTPUT – An LVDS Differential Transmitter drives the I2S Bus over an HDMI
Connector. Pinout is polarity adjustable for maximum flexibility.
•PARALLEL I2S OUTPUT – An RJ45 carries a buffered version of the I2S Bus for short distance use
•HIGH RESOLUTION CLOCKS – A pair of Ultra-Low Noise NDK NZ2520SDA oscillators drive the
WM8804 in non-PLL mode for the lowest possible noise.
•ULTRA-LOW NOISE LDO’s – Two Ultra-Low Noise LT3042 LDO’s (0.9 uV noise and 80 dB PSRR)
are used to supply the WM8804 and the NDK Clock’s.
•LINEAR PRE_REGULATOR - LT2941 LDO 5V pre-regulator allows the entire power chain to be linear
when an external linear PSU is used.
•LOW NOISE PCB LAYOUT –4-layer Split Ground PCB with noise reduction techniques refined from
years of High-Speed Mixed-Signal Design work.
•EXTRUDED ALUMINUM ENCLOSURE – Rugged, Aircraft Grade Aluminum, Anodized for Scratch
Resistance
•PRE-PROGRAMMED 32GB SD CARD - Mercury comes with a 32GB SD Card loaded with Volumio
3.x (other OS's TBD)
3.2 BLOCK DIAGRAM
Refer to the following figure for a block diagram of MERCURY V2 .

Pi 2 Design Mercury V2, Hardware Reference Manual – P1
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USB-A
HOST x2
HDMI 0
COMPUTE
MODULE 4
GPIO
I2C
I2S (Slave Mode)
+5V
WM8804 24-Bit
SPDIF Transmitter
(Master Mode)
I2S OUTPUT
I2C CONTROL
75 OHM
BNC
2.5MM
DC Jack
5V @ 5A
Switching Supply
RS-485
Balanced
Driver
1:1 Isolation
Transformer
1:1 Isolation
Transformer
SPDIF OUTPUT
MCLK IN
NDK NZ2520SDA
24.576Mhz OPTO
QUAD LVDS
TRANSMITTER HDMI
USB OTG
USB2504 4-PORT
USB2.0 HUB
UPSTRE M I/F
HOST PORT 0
HOST PORT 1
HOST PORT 2
HOST PORT 3
HDMI 0
HDMI 1
DSI 1
15-PIN
FLEX
GIGe I/FRJ-45
SD C RD I/F
uSD
SOCKET
M.2 2280
TYPE”M” SOCKET PCIe x1 I/F
3.3V @ 5A
Switching Supply
CLOCK
SELECT
Digital 3.3V
1:1 Isolation
Transformer RCA
NZ2520SDA
Power
WM8804
Power
NDK NZ2520SDA
22.792Mhz
LM2941 Low
Noise LDO
LT3042 LT3042
+12V +/- 20%
DC IN
USB 5V
HDMI 1
XOR POLARITY
BUFFER
4-POSITION
DIP SWITCH
4-BIT BUFFER RJ45
110 OHM
XLR
Figure 1 – MERCURY V2 Block Diagram

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4ON-BOARD DEVICES
4.1 OVERVIEW
MERCURY V2 interfaces to the CM4 via a pair of high density Hirose Connectors. This
section describes in detail the devices located on the Mercury Streamer.
4.2 COMPUTE MODULE 4
At the core of MERCURY V2 is the latest Raspberry Pi Compute Module 4. Designed
for low-powered embedded applications, this module runs the software required to
perform the Digital Audio Player function as well as other applications. Key features of
the CM4 (as used on the Mercury Streamer) are as follows:
•Broadcom BCM2711, Quad core Cortex-A72 (ARM v8) 64-bit SoC @ 1.5GHz
•H.265 (HEVC) (4Kp60 decode), H.264 (1080p60 decode, 1080p30 encode)
•OpenGL ES 3.0 graphics
•4GB or 8GB LPDDR4-3200 SDRAM
•2.4 GHz, 5.0 GHz IEEE 802.11 b/g/n/ac wireless
•Bluetooth 5.0, BLE
•Gigabit Ethernet PHY supporting IEEE 1588
•PCIe 1-lane Host, Gen 2 ( 5Gbps )
•USB 2.0 port
•UART, I2C and I2S Peripheral Ports
•Dual HDMI 2.0 ports (up to 4Kp60 supported)
•4-lane MIPI DSI display port
•SDIO 2.0
4.2 USB2504A USB HUB
MERCURY V2 uses the Microchip USB2504A to interface the CM4 with an external
dual USB2.0 Connector and an internal, vertical USB2.0 Connector. The signals of the
USB2504A and their use are described in the following table.
Signal Connection Description
USBD_N/P 0 CM4 USB_OTG Upstream Host port from CM4
USBD_N/P 1 Unused
USBD_N/P 2 Unused
USBD_N/P 3 P7 PORT A Dual USB Host Connector, Lower Port
USBD_N/P 4 P7 PORT B Dual USB Host Connector, Upper Port
Table 2 – USB2504A USB Hub Connections

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4.3 WM8804 SPDIF TRANSMITTER
At the core of MERCURY V2 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.
WM8804
Signal
CM4
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 GPIO6 0 = Select 22.5792Mhz Input Clock for 44.1Khz,
88.2Khz and 176.4Khz Frame Rates
1 = Select 24.576Mhz Input Clock for 48Khz,
92Khz and 192Khz Frame Rates
TXO - AES3/SPDIF encoded digital audio output
Table 3 – CM4 to WM8804 Connections
4.3.1 WM8804 SPDIF TRANSMITTER NOTES
1. The WM8804 is controlled using the I2C port. Refer to the WM8804
documentation and installed player software.
2. MERCURY V2 is designed to operate the WM8804 in Master mode. In
this mode the WM8804 receives its master clock from XIN and drives
MCLK (unused by the CM4), BCLK and LRCLK out. Serial Data in is
received from CM4.
4.4 DUAL HIGH RESOLUTION NDK CLOCKS
A pair of NDK NZ2520SDA Ultra-Low Noise clocks provide the critical timing signals for
the WM8804. They are selected via Compute Module 4 GPIO6 (0 = 22.5792Mhz and 1
= 24.576Mhz).
4.5 RS-485 DIFFERENTIAL TRANSMITTER
An RS-485 Differential Transmitter accepts the SPDIF output from the WM8804 and

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sends it as a balanced pair to the 1:1 Isolation Transformer and then to the XLR
connector.
4.6 I2S PARALLEL BUFFER
A 4-Bit Buffer is used to drive the I2S signals (MCLK, BCKL, LRCLK and SDO) to the
RJ45.
4.7 I2S DIFFERENTIAL DRIVER
A Quad Differential LVDS Driver takes the I2S Bus and converts each signal into a
balanced differential signal. This is then connected to an HDMI connector. This device
is designed to drive the I2S Bus up to 3 meters.

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5CM4 PORTS AND GPIO
5.1 OVERVIEW
MERCURY V2 uses several 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
usage for these ports on MERCURY V2 are listed below in the following table.
PORT/Signal(s) MERCURY V2
Use
Description
Ethernet P8 RJ45 Ethernet Port
*LED_ACT LED1 Green LED, CM4 Activity
*LED_PWR LED2 Red LED, Power
Analog_IP0-1 Unused
Camera_GPIO Unused
*EXT_RST *RST Reset Out to Peripherals
USB_P/N USB2504A USB Host to USB2504A Hub
USB_OTG_ID GND Host Mode Only
CAM0-1 Unused
DSI0 Unused
DSI1 P5 DSI Interface for LCD Display - unpopulated
PCIe P9 M.2 2280 NVMe Socket
HDMI0 P4 External HDMI Connector 0
HDMI1 P16 External HDMI Connector 1
Table 4 – CM4 Ports and Usage
5.2.1 CM4 PORT NOTES
1. Ports marked unused are unavailable and not connected on the Mercury
Streamer.
5.3 COMPUTE MODULE 4 GPIO
The CM4 provides a large number of General Purpose I/O (GPIO) pins. These pins also