PI 2 Design Pi 2 Media PI2AES Quick user guide

PI2Media PI2AES Hardware Reference Manual – P0.1 - 3/27/2019
PAGE 1
Pi
Pi Pi
Pi 2
22
2 Media
MediaMedia
Media
PI2AES
Digital Pro Audio Hat
Hardware Reference Manual
© 2017 PI 2 Design

PI2Media PI2AES Hardware Reference Manual – P0.1 - 3/27/2019
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Table of Contents
1 Warranty......................................................................................................................................................................................... 3
2 Operating Specifications ................................................................................................................................................................. 4
2.1 PI2AES Operating specifications ............................................................................................................................................. 4
3 Overview ........................................................................................................................................................................................ 5
3.1 Introduction ............................................................................................................................................................................. 5
3.2 Block Diagram......................................................................................................................................................................... 5
4 On-Board Devices .......................................................................................................................................................................... 7
4.1 Overview ................................................................................................................................................................................. 7
4.1 PI2AES I2C Bus Devices......................................................................................................................................................... 7
4.1 WM8804 SPDIF Transmitter.................................................................................................................................................... 7
4.1.1 WM8804 SPDIF Transmitter Notes .................................................................................................................................. 8
4.2 Dual High Resolution NDK Clocks........................................................................................................................................... 8
4.3 RS-422 Differential Transmitter ............................................................................................................................................... 8
4.4 I2S Parallel Buffer ................................................................................................................................................................... 8
4.5 I2S Differential Driver .............................................................................................................................................................. 8
4.6 Audio Data Rate and Power LED’s.......................................................................................................................................... 8
5 RPi GPIO........................................................................................................................................................................................ 9
5.1 Overview ................................................................................................................................................................................. 9
5.1.1 RPi GPIO Notes............................................................................................................................................................. 10
6 PI2AES Power.............................................................................................................................................................................. 11
6.1 Overview ............................................................................................................................................................................... 11
7 PI2AES Software.......................................................................................................................................................................... 12
7.1 Overview ............................................................................................................................................................................... 12
8 Top Side Connectors .................................................................................................................................................................... 13
8.1 Overview ............................................................................................................................................................................... 13
8.2 J1 – DC Jack......................................................................................................................................................................... 16
8.3 P1 – 40-Pin GPIO Header ..................................................................................................................................................... 16
8.4 P2 - I2S Expansion Header ................................................................................................................................................... 16
8.1 P3 – XLR Balanced Output.................................................................................................................................................... 17
8.2 P4 – I2S Over HDMI.............................................................................................................................................................. 17
8.3 U9 – Combo RCA/Opto Transmitter ...................................................................................................................................... 18
8.4 D1 – Triple LED..................................................................................................................................................................... 18
9 Document Revisions..................................................................................................................................................................... 19
10 Errata.......................................................................................................................................................................................... 20
10.1 Overview ............................................................................................................................................................................. 20
List of Tables
Table 1 – PI2AES Operating Specifications ....................................................................................................................................... 4
Table 2 – PI2AES I2C Bus Devices ................................................................................................................................................... 7
Table 3 – RPi to WM8804 Connections ............................................................................................................................................. 8
Table 4 – CPU GPIO Pin Assignments............................................................................................................................................ 10
Table 5 – I2S Expansion Header Pinout .......................................................................................................................................... 17
Table 6 – I2S Over HDMI Pinout...................................................................................................................................................... 18
Table 7 – Document Revisions ........................................................................................................................................................ 19
List of Figures
Figure 1 – PI2AES Block Diagram ..................................................................................................................................................... 6
Figure 2 – PI2AES Power, Simplified Block Diagram ....................................................................................................................... 11
Figure 3 – PI2AES Top View ........................................................................................................................................................... 14
Figure 4 – PI2AES Front View (shown mounted on Raspberry Pi)................................................................................................... 15
Figure 5 – PI2AES Side View (shown mounted on Raspberry Pi) .................................................................................................... 16

PI2Media PI2AES Hardware Reference Manual – P0.1 - 3/27/2019
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1
11
1WARRANTY
WARRANTYWARRANTY
WARRANTY
The enclosed product ("the Product"), a part of the PI2MEDIA Shield/Hat series, is
warranted by Pi 2 Design for a period of one year for reasonable development, testing
and use, all as further described and defined below. This warranty runs solely to the
individual or entity 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 user programming,
development 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 test or bus
Connector, 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. This Product is not intended to be used on or embedded in or otherwise
used in connection with any life-sustaining or life-saving product and this warranty is not
applicable nor is Pi 2 Design liable in any respect if the Product is so used.
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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2
22
2OPERATING
OPERATING OPERATING
OPERATING S
SS
SPECIFICATIONS
PECIFICATIONSPECIFICATIONS
PECIFICATIONS
2.1 PI2AES OPERATING SPECIFICATIONS
The PI2AES conforms to the following specifications:
Specification Value
Dimensions 85mm x 56.5mm
Weight ~10g
Storage Temperature -20C to +85C
Operating Temperature 0C to +70C
Humidity 0% to 95% RH, Non-Condensing
Input Voltage (VIN) +12V to +48V
Power Consumption 250mw Typical, 1W Maximum
Table 1 – PI2AES Operating Specifications

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3
33
3OVERVIEW
OVERVIEWOVERVIEW
OVERVIEW
3.1 INTRODUCTION
The PI2AES, designed and manufactured by PI 2 Design, is a professional I/O Shield
designed to bring Professional Studio Grade Audio to the Raspberry PI ®family of
Single Board Computers. This low-cost Shield converts the Raspberry Pi ®I2S
Interface to High Definition Digital Audio Coax, OPTO and Balanced XLR.
The addition of Parallel I2S Output along with LVDS Differential over HDMI allows the
PI2AES to interface with virtually any High Performance DAC on the market.
The major features of the PI2AES are as follows:
•FORM FACTOR – Raspberry Pi ®Shield Size w/40-Pin mating connector.
•AES TRANSMITTER – The industry standard WM8804 converts the RPi 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 via RCA Jack
•SPDIF OPTICAL OUTPUT – Isolated Optical Transmitter Drives Consumer Level DAC and AVR
•BALANCED OUTPUT – An RS-422 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 – A DS2063 Differential Transmitters is used to drive the I2S Bus over
a standard HDMI Connector. The Pinout is Selectable Between the PS Audio and Gustard Standards.
•HIGH RESOLUTION CLOCKS – A pair of Ultra-Low Noise NDK NZ2520SD oscillators allow the
WM8804 to operate in non-PLL mode for the lowest possible noise.
•ULTRA-LOW NOISE LDO’s – Ultra-Low Noise AP1155ADL LDO (30uV noise and 80dB PSRR) is
used to Supply the WM8804 Transmit Section, while an ADP150 (9uV noise and 70dB PSRR) and
the High-Resolution Clocks.
•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
Refer to the following figure for a block diagram of the PI2AES Shield.

PI2Media PI2AES Hardware Reference Manual – P0.1 - 3/27/2019
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CLIFF OTJ6
PI2AES BLOCK DIAGRAM
PI2AES BLOCK DIAGRAMPI2AES BLOCK DIAGRAM
PI2AES BLOCK DIAGRAM
USB-A
HOST
USB-A
HOST
USB-A
HOST
USB-A
HOST
10/100 RJ45
w/Transformer
HDMI
40-Pin Expansion Header
GPIO
I2C
I2S (Slave Mode)
Raspberry Pi ® or Clone
w/40-PIN GPIO Header
+5V
AP1155
LDO
WM8804 24-Bit
SPDIF Transmitter
(Master Mode)
I2S O P T
I2C CONTROL
Clock
Select
NDK NZ2520SD
22.792Mhz
RCA
2.5MM
DC Jack
5V @ 5A
Switching Supply
RS-422
Balanced
Driver
1:1 Isolation
Transformer
1:1 Isolation
Transformer
SPDIF O TP T
MCLK IN
40-Pin Socket
NDK NZ2520SD
24.576Mhz
AP1155
LDO
TOSLINK
OPTO
QUAD
BUFFER
QUAD LVDS
TRANSMITTER
I2S, I2C & PWR
EXPANSION
HEADER
HDMI
5V
Figure 1 – PI2AES Block Diagram

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4
44
4O
OO
ON
NN
N-
--
-BOARD DEVICES
BOARD DEVICESBOARD DEVICES
BOARD DEVICES
4.1 OVERVIEW
The PI2AES interfaces to the RPi via the 40-Pin GPIO Connector. This section
describes in detail the devices located on the PI2AES.
4.1 PI2AES I2C BUS DEVICES
The following table describes the CPU I2C Bus usage of the PI2AES. Most of these
addresses are set by the startup script supplied by Pi2Design. Refer to the respective
device documentation for more detail.
I2C
Bus
7-Bit I2C
Address
Description
I2C 0x3B WM8804 SPDIF Transmitter
Table 2 – PI2AES I2C Bus Devices
4.1 WM8804 SPDIF TRANSMITTER
At the core of the PI2AES is the Cirrus Logic WM8804 AES Digital Audio Transmitter.
This device interfaces to the Raspberry Pi via I2S and I2C. The signals used to interface
with the WM8804 are shown in the following table.
WM8804
Signal
RPi
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 GPIO5 1 = Select 22.5792Mhz Input Clock for 44.1Khz,
88.2Khz and 176.4Khz Frame Rates
XIN GPIO6 1 = Select 24.576Mhz Input Clock for 48Khz,
96Khz and 192Khz Frame Rates

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TXO - AES3/SPDIF encoded digital audio output
Table 3 – RPi to WM8804 Connections
4.1.1 WM8804 SPDIF TRANSMITTER NOTES
1. The WM8804 is controlled using the I2C port. Refer to the WM8804
documentation and Pi 2 Design supplied driver code for more detail.
2. The PI2AES is designed to operate the WM8804 in Master mode. In this
mode the WM8804 receives its master clock from XIN and drives MCLK
(unused), BCLK and LRCLK to the Pi. Serial Data in is received from Pi.
3. Pi GPIO’s 6 and 13 are used to select the desired clock input. GPIO 6 and
13 are pulled low by default. CAUTION - Do not select more than one
clock at a time!
4.2 DUAL HIGH RESOLUTION NDK CLOCKS
A pair of NDK NZ2520SD Ultra-Low Noise clocks provide the critical timing signals for
the WM8804. They are selected via Raspberry PI GPIO5 (22.5792Mhz) and GPIO6
(24.576Mhz).
4.3 RS-422 DIFFERENTIAL TRANSMITTER
An RS-422 Differential Transmitter accepts the SPDIF output from the WM8804 and
sends it as a balanced pair to the 1:1 Isolation Transformer and then to the XLR
connector.
4.4 I2S PARALLEL BUFFER
A 74FCT125 CMOS Buffer is used to drive the I2S signals (MCLK, BCKL, LRCLK and
SDO) to the I2S Expansion Header. This device is designed to drive the I2S Bus short
distances (<12 inches).
4.5 I2S DIFFERENTIAL DRIVER
A DS2063 Quad Differential LVDS Driver takes the I2S Bus and converts each signal
into a balanced differential signal. This is then connected to the HDMI connector. This
device is designed to drive the I2S Bus up to 3 meters.
4.6 AUDIO DATA RATE AND POWER LED’S
A triple stack LED is used to provide visual indication of: Power On (Green), Audio Data
Rate of 48/96/192Khz (Yellow) and Audio Data Rate of 44.1/88.2/176.4Khz (Red).

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5
55
5R
RR
RPI
PI PI
PI GPIO
GPIOGPIO
GPIO
5.1 OVERVIEW
The PI2AES uses a number of signals from the RPi GPIO header for control and status
purposes. This usage is defined in the following table.
RPi
PIN
DIR AF PUP/
PDN
PI2AES
Name
Description/Notes
1 - - - - RPi +3.3V - Unused
2 - - - +5V +5V Power to/from the RPi
3 I/O Y PUP I2C_SDA I2C Bus Data
4 - - - +5V +5V Power to/from the RPi
5 OUT Y PUP I2C_SCL I2C Bus Clock
6 - - - GND
7 OUT - - GPIO4 Unused
8 - - - GPIO14 Unused
9 - - - GND Unused
10 - - - GPIO15 Unused
11 - - - GPIO17 Unused
12 IN Y - BCLK I2S Bit Clock from WM8804
13 - - - GPIO27 Unused
14 - - - GND
15 - - - GPIO22 Unused
16 - - - GPIO23 Unused
17 - - - - RPi +3.3V - Unused
18 - - - GPIO24 Unused
19 - - - GPIO10 Unused
20 - - - GND
21 - - - GPIO9 Unused
22 - - - GPIO25 Unused

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RPi
PIN
DIR AF PUP/
PDN
PI2AES
Name
Description/Notes
23 - - - GPIO11 Unused
24 - - - GPIO8 Unused
25 - - - GND
26 - - - GPIO1 Unused
27 I/O Y - ID_SDA Unused
28 OUT Y - ID_SCL Unused
29 - - - GPIO5 1 = Select 22.5792Mhz Clock Input to WM8804
30 - - - GND
31 OUT - PUP GPIO6 1 = Select 24.576Mhz Clock Input to WM8804
32 - - - GPIO12 Unused
33 OUT - - GPIO13 Unused
34 - - - GND
35 IN Y - LRCLK I2S Left/Right Clock from WM8804
36 - - - GPIO16 Unused
37 - - - GPIO26 Unused
38 - - - GPIO20 Unused
39 - - - GND
40 OUT Y - SDOUT Pi I2S Serial Audio Data Out
Table 4 – CPU GPIO Pin Assignments
5.1.1 RPI GPIO NOTES
1. DIR is from the point of view of the RPi.
2. Y in the Alternate Function (AF) column indicates that the use of this pin
requires the pin to be assigned to the function as defined by the RPi
specifications.
3. PUP/PDN indicates if the GPIO should have its associated Pullup (PUP)
or Pulldown (PDN) resistor enabled.
4. An asterisk ‘*’ at the beginning of the name indicates a low true signal.

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PI2AES
PI2AESPI2AES
PI2AES POWER
POWERPOWER
POWER
6.1 OVERVIEW
The PI2AES is designed to be powered from an external +12V to +48V source. Jumper
W2, when installed, allows the Raspberry PI to be powered from the PI2AES. When
jumper W2 is removed, separate 5V power must be supplied to the Raspberry PI.
Note that an on-board protection circuit insures proper operation when jumper W2 is
installed while power is applied via J1 AND from the Pi (P1) simultaneously.
See the below block diagram for a simplified view of the PI2AES power.
TPS54560, 5V @ 5A
SWITCHING REGULATOR
J1
.5MM JACK
RESETABLE
POLY FUSE
+1 V to +48V
DC INPUT
58V
OVER PROTECTION
AP1155, 3.3V
LOW NOISE LDO
ADP150, 3.3V
LOW NOISE LDO
+3.3V to Digital Logic
+3.3V to NDK CLOCKS
BIDIRECTIONAL
POWER
PROTECTION
RASPBERRY PI
40-PIN HDR
5V PINS
W
EXPANSION
HEADER POWER PINS
PI2AES POWER FLOW
SIMPLIFIED BLOCK DIAGRAM
W1
+5V to HDMI Connector
Figure 2 – PI2AES Power, Simplified Block Diagram

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77
7PI2AES
PI2AESPI2AES
PI2AES SOFTWARE
SOFTWARESOFTWARE
SOFTWARE
7.1 OVERVIEW
Due to the various resources interfaced on the PI2AES, both internal and external to the
RPi, 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. See our web site at http://www.pi2design.com or
email us at [email protected] for example operating and initialization code.

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88
8TOP SIDE CONNECTORS
TOP SIDE CONNECTORSTOP SIDE CONNECTORS
TOP SIDE CONNECTORS
8.1 OVERVIEW
This section provides the type, location and pinout for the various connectors on the
PI2AES. Top View and Front View are shown in the following 3D renders.

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Figure 3 – PI2AES Top View
J3
P3
BALANCED AES XLR
U9
RCA COAX
AND OPTO
J1
2.5MM
DC JACK
P4 – I2S
OVER
HDMI
P3
–
I2
S EXPANSION
HEADER
W1
W2
HEA
D1
PIN 1
PIN 1
6

PI2Media PI2AES Hardware Reference Manual – P0.1 - 3/27/2019
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Figure 4 – PI2AES Front View (shown mounted on Raspberry Pi)
U9
OPTO
U9
COAX
D1
44.1K
48K
PWR
P3
AES
BALANCED

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Figure 5 – PI2AES Side View (shown mounted on Raspberry Pi)
8.2 J1 – DC JACK
This jack is designed to accept a 5.5mm x 2.5mm center positive plug for external
power in. Voltage must be +12V to +48V.
8.3 P1 – 40-PIN GPIO HEADER
This is a standard 40-Pin .1” Dual Row Female Header. It is designed to accept a
Raspberry Pi single board and conforms to the standard Raspberry Pi 40-Pin GPIO
Header pinout.
8.4 P2 - I2S EXPANSION HEADER
This is a 16-Pin, .1” Single Row Header that carries I2S, I2C, and Power for expansion
use. The Pinout for P2 is shown in the following table.
P2 PIN Name Description
1 5V +5V direct from Regulator
2 5V +5V direct from Regulator
3 GND Ground
P1 – I2S
HDMI J1 – DC
JACK

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4 MUTE 1 = Mute On
5 SCL I2C Clock
6 SDA I2C Data
7 GND Ground
8 SDO Buffered I2S Data
9 LRCLK Buffered I2S Left/Right (Word) Clock
10 BCLK Buffered I2S Bit Clock
11 GND Ground
12 MCLK Buffered I2S Master Clock
13 GND Ground
14 *PSW Power Enable – Jumper with Pin 13 for auto on
15 VIN +12V to +48V Input
16 VIN +12V to +48V Input
Table 5 – I2S Expansion Header Pinout
8.1 P3 – XLR BALANCED OUTPUT
P3 is a 3-Pin XLR Connector. This 100-ohm connector carries the balanced digital
audio output.
8.2 P4 – I2S OVER HDMI
P4 is a standard HDMI Connector that carries the Differential I2S signal. Pinout
conforms to either the PS Audio (default) or Gustard standards. The Pinout for P4 is
shown in the following table.
P4 PIN Name Description
PS Audio Pinout
Description
Gustard Pinout
1 SDO+ I2S Data Plus I2S Data Plus
2 GND Ground Ground
3 SDO- I2S Data Minus I2S Data Minus
4 BCK+ I2S Bit Clock Plus I2S Bit Clock Minus
5 GND Ground Ground
6 BCK- I2S Bit Clock Minus I2S Bit Clock Plus

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P4 PIN Name Description
PS Audio Pinout
Description
Gustard Pinout
7 LRCLK+ I2S Left/Right Clock Plus I2S Left/Right Clock Minus
8 GND Ground Ground
9 LRCLK- I2S Left/Right Clock Minus I2S Left/Right Clock Plus
10 MCLK+ I2S Master Clock Plus I2S Master Clock Plus
11 GND Ground Ground
12 MCLK- I2S Master Clock Minus I2S Master Clock Minus
13 NC No Connect No Connect
14 NC No Connect No Connect
15 SDA I2C Data I2C Data
16 SCL I2C Clock I2C Clock
17 GND Ground Ground
18 +5V +5V from
Jumper W1
+5V from
Jumper W1
19 NC No Connect No Connect
Table 6 – I2S Over HDMI Pinout
8.3 U9 – COMBO RCA/OPTO TRANSMITTER
U9 is a Cliff OTJ6 that contains the RCA for AES COAX digital audio output and a
Toslink Transmitter for SPDIF Optical digital audio output.
8.4 D1 – TRIPLE LED
D1 Is a stacked triple LED for indicating: Power ON (Green); 48Khz/96Khz/192Khz
Clock Base (Yellow); and 44.1Khz/88.2Khz/176.4Khz Clock Base (Red).

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99
9DOCUMENT REVISIONS
DOCUMENT REVISIONSDOCUMENT REVISIONS
DOCUMENT REVISIONS
Date Revision Change
03/26/2019 P0.1 Preliminary Release
Table 7 – Document Revisions

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10
1010
10 ERRATA
ERRATAERRATA
ERRATA
10.1 OVERVIEW
There are currently no known errata for the PI2AES Rev. P1.