PI 2 Design Mercury Streamer Quick user guide

Pi 2 Design Mercury Streamer, Hardware Reference Manual – P8
PAGE 1
Pi 2 Design
Mercury Streamer
Hardware Reference Manual
© 2022 PI 2 Design

Pi 2 Design Mercury Streamer, Hardware Reference Manual – P8
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Table of Contents
1 Warranty......................................................................................................................................................................................... 3
2 Operating Specifications ................................................................................................................................................................. 4
2.1 Mercury Streamer Operating specifications ............................................................................................................................. 4
3 Overview ........................................................................................................................................................................................ 5
3.1 Introduction ............................................................................................................................................................................. 5
3.2 Block Diagram......................................................................................................................................................................... 6
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 .................................................................................................................................................... 9
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............................................................................................................................................... 11
5.3.1 CM4 GPIO Notes....................................................................................................................................................... 12
6 Mercury Streamer Power ........................................................................................................................................................ 13
6.1 Overview........................................................................................................................................................................ 13
7 Mercury Streamer Software .................................................................................................................................................... 15
8 Connector Locations............................................................................................................................................................... 16
8.1 Overview........................................................................................................................................................................ 16
8.2 Front and Rear PaneL and Interior Views....................................................................................................................... 16
8.3 P1 – Expansion I/O Connector....................................................................................................................................... 18
8.3 P2 – Micro-USB, FACTORY USE ONLY........................................................................................................................ 19
8.4 P3 – Console UART, FACTORY USE ONLY ................................................................................................................. 19
8.5 P4 – HDMI 0 .................................................................................................................................................................. 19
8.6 P5 – DSI ........................................................................................................................................................................ 19
8.7 P6 – 5V Header, FACTORY USE ONLY........................................................................................................................ 20
8.8 P7 – Dual USB............................................................................................................................................................... 20
8.9 P8 – Gigabit Ethernet..................................................................................................................................................... 20
8.10 P9 – M.2 2280 NVMe..................................................................................................................................................... 20
8.11 P10 – BNC AES Single Ended....................................................................................................................................... 20
8.12 P11 – XLR AES Balanced.............................................................................................................................................. 20
8.13 P12 – DC Input .............................................................................................................................................................. 20
8.15 P13 – Expansion Power Connector................................................................................................................................ 20
8.15 P14 –USB ...................................................................................................................................................................... 21
8.16 P15 – I2S Over HDMI .................................................................................................................................................... 21
8.17 P16 HDMI 1 ................................................................................................................................................................... 22
8.18 U15 – Combo RCA/Opto Transmitter ............................................................................................................................. 22
8.19 D7, D8 – Speed LED’s ................................................................................................................................................... 22
8.20 SD1 – Micro-SD Card .................................................................................................................................................... 22
9 Document Revisions ............................................................................................................................................................... 23
10 Errata...................................................................................................................................................................................... 24
10.15 Overview ................................................................................................................................................................... 24
List of Figures
Figure 1 – Mercury Streamer Block Diagram ..................................................................................................................................... 6
Figure 2 – Mercury Streamer Power, Simplified Block Diagram ....................................................................................................... 13
Figure 3 – Mercury Streamer Power Control Schematic................................................................................................................... 13
Figure 4 – Mercury Streamer Front Panel........................................................................................................................................ 16
Figure 4 – Mercury Streamer Rear Panel......................................................................................................................................... 17
Figure 4 – Mercury Streamer Internal View...................................................................................................................................... 18

Pi 2 Design Mercury Streamer, Hardware Reference Manual – P8
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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 STREAMER OPERATING SPECIFICATIONS
The Mercury Streamer conforms to the following specifications:
Specification Value
Dimensions 170mm x 123.2mm x 53.5mm (6.7” x 4.85” x 2.1”)
Weight ~1kg (2 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 3W Typical, 8W Maximum (not including SSD)
Table 1 – Mercury Streamer Operating Specifications

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3OVERVIEW
3.1 INTRODUCTION
The Mercury Streamer, designed and manufactured by PI 2 Design, is a Compute
Module 4 based device designed for Professional, Studio Grade, Digital Audio
Streaming. The Mercury Streamer 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 Mercury Streamer to optimally
interface with virtually any High Performance DAC on the market.
The major features of the Mercury Streamer 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 2280 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.
•INTERNAL USB - A vertical USB2.0 Connector is provided to interface with LCD Touch Screens for
Internal display-based systems.
•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 for Internal
display-based systems.
•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
Coaxial Transmission of the Digital Audio Data @1V AES Standard Level.
•AES 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
•TOSLINK OPTICAL OUTPUT – Isolated Optical Transmitter Drives Consumer Level DAC’s
•SPDIF COAX OUPUT - A 1:1 Isolation Transformer provides Bit Perfect Impedance Controlled
Coaxial Transmission of the Digital Audio Data @0.6V Consumer Standard Level.
•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. Additionally, these
are fed from an LT2941 LDO used as a 5V pre-regulator. This allows the entire power chain to be
linear (assuming an external linear supply is used).
•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.
•EXTRUDED ALUMINUM ENCLOSURE – Rugged, Aircraft Grade Aluminum, Anodized for Scratch
Resistance

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3.2 BLOCK DIAGRAM
Refer to the following figure for a block diagram of the Mercury Streamer.
CLIFF OTJ-6
USB-A
HOST x2
HDMI
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
4-BIT
BUFFER
QUAD LVDS
TRANSMITTER
I2S, I2C & PWR
EXPANSION
FLEX
CONNECTORS
HDMI
5V
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
VERTICAL
HDMI 0
HDMI 1
USB2.0
VERTICAL
DSI 1
15-PIN
FLEX
GIGe I/F
RJ-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
+7V to +18V
DC IN
USB 5V
Figure 1 – Mercury Streamer Block Diagram

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4ON-BOARD DEVICES
4.1 OVERVIEW
The Mercury Streamer 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 the Mercury Streamer 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
The Mercury Streamer 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 P14 Internal Vertical USB Host Connector
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 the Mercury Streamer 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. The Mercury Streamer 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
I2S Expansion Flex Connector. This device is designed to drive the I2S Bus short
distances (<12 inches).
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.
4.8 AUDIO DATA RATE LED’S
Two LED’s provide visual indication of the selected Audio Data Rate, 48/96/192Khz
(Yellow) and 44.1/88.2/176.4Khz (Red).

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5CM4 PORTS AND GPIO
5.1 OVERVIEW
The Mercury Streamer 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 the Mercury Streamer are listed below in the following table.
PORT/Signal(s) Mercury
Streamer 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 USEL Factory use only
CAM0-1 Unused
DSI0 Unused
DSI1 P5 DSI Interface for LCD Display
PCIe P9 M.2 2280 NVMe Socket
HDMI0 P4 External HDMI Connector
HDMI1 P16 Internal, Vertical HDMI Connector
UART 1 P3 Serial Console
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.
2. USB_OTG is used for factory programming of CM4 eMMC. This is only

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used with CM4 modules that have built in eMMC. Non-eMMC modules
use the SDIO port as the storage. USB_OTG Function is not available by
default.
5.3 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 Mercury Streamer are described in the
following table.
GPIO DIR AF PUP
PDN
Mercury
Streamer
Usage
Description/Notes
0 I/O I2C0 PUP SDA0 Routed to P5 for DSI 0
1 I/O I2C0 PUP SCL0 Routed to P5 for DSI 0
2 I/O I2C1 PUP SDA I2C Data for Mercury Streamer and
Expansion
3 I/O I2C1 PUP SCL I2C Clock for Mercury Streamer and
Expansion
4 I/O GPIO4 Routed to P1 Expansion Connector
5 I/O GPIO5 Routed to P1 Expansion Connector
6 I/O GPIO6 WM8804 Master Clock Select
7 - unused
8 - unused
9 - unused
10 - unused
11 - unused
12 - unused
13 - unused
14 OUT UART1 TXD Routed to P3 Header
15 IN UART1 RXD Routed to P3 Header
16 - unused
17 - unused

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GPIO DIR AF PUP
PDN
Mercury
Streamer
Usage
Description/Notes
18 IN I2S BCLK I2S Bit Clock from WM8804
19 IN I2S WCLK I2S Word Clock from WM8804
20 - unused
21 OUT I2S SDOUT I2S Serial Data to WM8804
22 OUT PUP PHLD Power Hold to Power Circuit
23 IN PUP *ROT_SW Rotary Center Switch, Routed to P17
24 IN PUP *PSW Power On Switch from Power Circuit
25 IN PUP ROT_CK Rotary Clock Switch, Routed to P17
26 IN PUP ROT_DT Rotary Data Switch, Routed to P17
27 I/O GPIO27 Routed to P1 Expansion Connector
Table 5 – CM4 Port and GPIO Pin Assignments
5.3.1 CM4 GPIO NOTES
3. DIR is from the point of view of the CM4.
4. Alternate Function (AF) column indicates that the use of this pin requires
the pin to be assigned to the named function as defined by the CM4
specifications.
5. PUP/PDN indicates if the GPIO should have its associated Pullup (PUP)
or Pulldown (PDN) resistor enabled.
6. An asterisk ‘*’ at the beginning of the name indicates a low true signal.

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6MERC RY STREAMER POWER
6.1 OVERVIEW
The Mercury Streamer is designed to be powered from an external +12V source.
See the block diagram below for a simplified view of the Mercury Streamer power flow.
FAN23SV06, 5V @ 5A
SWITCHING REGULATOR
2.5MM JACK
RESETABLE
POLY FUSE
12V /- 20%
DC INPUT
OVER VOLTAGE
PROTECTION LT3042, 3.3V
LOW NOISE LDO
LT3042, 3.3V
LOW NOISE LDO
3.3V to
WM8804
3.3V to
NDK CLOCKS
COMPUTE
MODULE 4
AND USB
LT2941, 5V
PRE-REGULATOR
CM4 ES POWER
BLOCK DI GR M
FAN23SV06, 3.3V @ 5A
SWITCHING REGULATOR
3.3V to
CM4AES
POWER
CONTROL
TO AES
BUFFERS
Figure 2 – Mercury Streamer Power, Simplified Block Diagram
6.2 POWER CONTROL
This circuit allows software to monitor and control the power state of the Mercury
Streamer. It uses two GPIO to perform the Power Hold and Power State functions. This
circuit is compatible with the Volumio 503HTA Plug-In. Note that by default the circuit
simply follows the state of the Pushbutton Power Switch.
This circuit is shown in the figure below.
Figure 3 – Mercury Streamer Power Control Schematic

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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). When high it indicates that the user has placed the switch into the off
position (non-depressed) thus opening the on/off switch. Note that for proper operation
this circuit requires user software to program GPIO24 as an input with the internal
pullup enabled.
6.4 POWER HOLD
GPIO22 (PHLD) allows the CM4 to hold the power on even after the user puts the
Power Switch into the off position. After initialization, software can drive GPIO22 high,
thus holding the power on regardless of the state of the on/off switch. Driving this low,
removes this hold condition. Note that for proper operation this requires user software to
program GPIO24 as an output with the internal pullup disabled.

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7MERC RY STREAMER SOFTWARE
7.1 OVERVIEW
Due to the various resources interfaced on the Mercury Streamer, 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.
7.2 COMPATIBLE DRIVER
Most Audio Player software will support Mercury using either the “Pi2design PI2AES” or
“HifiBerry Digi+ Pro” driver.
7.3 USB HOST
Unlike the Raspberry Pi 4, the CM4 ROM Firmware does not enable the USB Host
functionality by default. It is necessary to initialize this by adding the following line to
cfg_boot.txt. Note that some player software will over-write this during an update but
may offer an alternate location that is safe from updates.
To enable the USB 2.0 ports on the Compute Module 4, you need to edit the boot config
file (/boot/config.txt) and add:
dtoverlay=dwc2,dr_mode=host
7.4 PCIE SSD CONFIGURATION
This section is %TBD%

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8CONNECTOR LOCATIONS
8.1 OVERVIEW
This section provides the type, location, and pinout for the various connectors on the
Mercury Streamer.
8.2 FRONT AND REAR PANEL AND INTERIOR VIEWS
This shows the front and rear panels of the Mercury Streamer as well as an internal
view of the PCB.
Figure 4 – Mercury Streamer Front Panel

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Figure 5 – Mercury Streamer Rear Panel

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Figure 6 – Mercury Streamer Internal View
8.3 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
1 MCLK Buffered I2S Master Clock
2 GND Ground
3 BCLK Buffered I2S Bit Clock
4 GND Ground
P15
I2S P11
BALANCED AES P10
AES
U15
COAX
OPTO
P9
ETHERNET SD1
SD-CARD
P4
HDMI 0
P7
DUAL USB
P1
P17 P3
P5
P14
USB
P16
HDMI 1
P9
M.2 2280
P13
SW1
P12

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5 LRCLK Buffered I2S Left/Right (Word) Clock
6 GND Ground
7 SDO Buffered I2S Data
8 GND Ground
9 RSVD Connected to CM4 GPIO20
10 *PSW Power Enable – Low True
11 RSVD Connected to CM4 GPIO27
12 *RST Reset from CM4
13 RSVD Connected to CM4 GPIO4
14 RSVD Connected to CM4 GPIO5
15 GND Ground
16 SCL I2C Clock
17 SDA I2C Data
18 *ALED Connected to CM4 Activity LED Signal
19 *PLED Connected to CM4 Power LED Signal
20 GND Ground
Table 6 – Expansion I/O Connector Pinout
8.3 P2 – MICRO-USB, FACTORY USE ONLY
P2 is a standard USB2.0 Micro-B connector and conforms to the industry standard
USB2.0 Pinout. It is connected to the CM4 USB OTG Port via a 2:1 switch. It is provided
to allow programming of CM4 modules with built-in eMMC. It is not used for modules
that have no eMMC. This connector is not populated by default.
8.4 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.
8.5 P4 – HDMI 0
P4 is a standard right angle HDMI female connector and conforms to the industry
standard HDMI Pinout. It is connected to CM4 HDMI Port 0.
8.6 P5 – DSI
P4 is an Amphenol HLW20S-2C7LF 20-Pin 1MM Pitch Flex connector and conforms to

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the CM4 DSI Pinout. It is connected to CM4 DSI Port 1.
8.7 P6 – 5V HEADER, FACTORY USE ONLY
P6 is a 2x1 2.54mm pitch, single row connector It is connected to the on-board +5V
Switch Supply. Pinout is: Pin1 - +5V; Pin 2 – GND.
8.8 P7 – DUAL USB
P7 is a standard Dual USB2.0 Host connector and conforms to the industry standard
USB2.0 Pinout. It is connected to the USB2504A USB Hub, Ports 3 (top) and 4
(bottom).
8.9 P8 – GIGABIT ETHERNET
P8 is a standard RJ45 and conforms to the industry Pinout. It is connected to the CM4
Ethernet Port.
8.10 P9 – M.2 2280 NVME
P9 is an industry standard M.2 Connector. The supported NVMe modules are 2280
(22mm x 80mm), “M” or “B” keyed. It is connected to the CM4 PCIe Port.
8.11 P10 – BNC AES SINGLE ENDED
P10 is a right-angle BNC Female. This 75-ohm connector carries the Single Ended AES
Digital Audio output.
8.12 P11 – XLR AES BALANCED
P3 is a 3-Pin XLR Connector. This 100-ohm connector carries the Balanced AES Digital
Audio output.
8.13 P12 – DC INPUT
P12 is a 2x1 2.54mm pitch, JST B2B-XH-A shrouded connector. It is connected to the
Input Power Circuit.
8.15 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
1 GND Ground
2 VCC3 +3.3V from On-Board Switching Supply
3 GND Ground