PI 2 Design PI2AES-LITE Quick user guide

Pi 2 Design – PI2AES-LITE Hardware Reference Manual – P2.0 - 12/8/2022
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Pi 2 Design
PI2AES-LITE
Digital Pro Audio Hat
Hardware Reference Manual
© 2022 PI 2 Design

Pi 2 Design – PI2AES-LITE Hardware Reference Manual – P2.0 - 12/8/2022
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Table of Contents
1 Warranty......................................................................................................................................................................................... 3
2 Operating Specifications ................................................................................................................................................................. 4
2.1 PI2AES-LITE 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-LITE 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 3.3V to 5V Buffer..................................................................................................................................................................... 8
5 RPi GPIO........................................................................................................................................................................................ 9
5.1 Overview ................................................................................................................................................................................. 9
5.1.1 RPi GPIO Notes............................................................................................................................................................. 10
6 PI2AES-LITE Power .................................................................................................................................................................... 11
6.1 Overview ............................................................................................................................................................................... 11
7 PI2AES-LITE Software ................................................................................................................................................................ 12
7.1 Overview ............................................................................................................................................................................... 12
8 Connectors ................................................................................................................................................................................... 13
8.1 Overview ............................................................................................................................................................................... 13
9 Document Revisions..................................................................................................................................................................... 14
10 Errata.......................................................................................................................................................................................... 15
10.1 Overview ............................................................................................................................................................................. 15
11 Case Assembly........................................................................................................................................................................... 16
11.1 Overview ............................................................................................................................................................................. 16
11.2 Part DescriPtions................................................................................................................................................................. 16
11.3 Assembly Step 1 ................................................................................................................................................................. 18
11.4 Assembly Step 2 ................................................................................................................................................................. 19
11.5 Assembly Step 3 ................................................................................................................................................................. 20
11.6 Assembly Step 4 ................................................................................................................................................................. 21
11.7 Assembly Step 5 ................................................................................................................................................................. 22
List of Tables
Table 1 – PI2AES-LITE Operating Specifications .............................................................................................................................. 4
Table 2 – PI2AES-LITE I2C Bus Devices.......................................................................................................................................... 7
Table 3 – RPi to WM8804 Connections ............................................................................................................................................. 8
Table 4 – CPU GPIO Pin Assignments............................................................................................................................................ 10
Table 4 – PI2AES-LITE Connector Locations .................................................................................................................................. 13
Table 7 – Document Revisions ........................................................................................................................................................ 14
List of Figures
Figure 1 – PI2AES-LITE Block Diagram............................................................................................................................................ 6
Figure 2 - PI2AES-LITE Acrylic Case Parts ..................................................................................................................................... 17

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1WARRANTY
WARRANTYWARRANTY
WARRANTY
The enclosed product ("the Product"), a part of the P2 2 Design 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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2OPERATING
OPERATINGOPERATING
OPERATING S
SS
SPECIFICATIONS
PECIFICATIONSPECIFICATIONS
PECIFICATIONS
2.1 PI2AES-LITE OPERATING SPECIFICATIONS
The PI2AES-LITE conforms to the following specifications:
Specification Value
Dimensions 65mm x 56.5mm – Hat Compliant
Weight ~8oz
Storage Temperature -20C to +85C
Operating Temperature 0C to +70C
Humidity 0% to 95% RH, Non-Condensing
Input Voltage (VIN) +5V +/- 5% from the Raspberry PI
Power Consumption 250mw Typical, 1W Maximum
Table 1 – PI2AES-LITE Operating Specifications

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3OVERVIEW
OVERVIEWOVERVIEW
OVERVIEW
3.1 INTRODUCTION
The PI2AES-LITE , 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, SPDIF Coax and Toslink Optical.
The major features of the PI2AES-LITE are as follows:
•FORM FACTOR – Raspberry Pi ®HAT Size w/40-Pin mating connector.
•AES TRANSMITTER – The industry standard WM8804 converts the PI
I2S stream to AES3/SPDIF 24-Bit Data up to 192Khz.
•AES COAX OUTPUT – A 1:1Isolation Transformer provides 75-ohm Impedance
Controlled Transmission of the Digital Audio Data via AES Standard BNC.
•SPDIF OUTPUT – A 1:1 Isolation Transformer provides Bit Perfect Transmission of
the Digital Audio Data via RCA Jack.
•TOSLINK OPTICAL OUTPUT – Isolated Optical Transmitter Supports Consumer
Level DAC’s.
•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 – Dual, Ultra-Low Noise LT34042 LDO’s (0.9uV noise
and 80dB PSRR) are used to supply the WM8804 AES Transmitter and the High-
Resolution NDK Clocks for extremely low Jitter.
3.2 BLOCK DIAGRAM
Refer to the following figure for a block diagram of the PI2AES-LITE Shield.

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PI2AES-LITE BLOCK DIAGRAM
40-Pin Expansion Header
GPIO
I2C
I2S (Slave Mode)
Raspberry Pi ® 3, 3+, 4
w/40-PIN GPIO Header
+5V
LT3042
LDO
WM8804 24-Bit
SPDIF Transmitter
(Master Mode)
I2S O P T
I2C CONTROL
Clock
Select
NDK NZ2520SD
22.792Mhz RCA
1:1 Isolation
Transformer
1:1 Isolation
Transformer
SPDIF O TP T
MCLK IN
40-Pin Socket
NDK NZ2520SD
24.576Mhz
LT3042
LDO
TOSLINK
OPTO
5V
Buffer
BNC
JUMPER
Figure 1 – PI2AES-LITE Block Diagram

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4
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4ON
ONON
ON-
--
-BOARD DEVICES
BOARD DEVICESBOARD DEVICES
BOARD DEVICES
4.1 OVERVIEW
The PI2AES-LITE interfaces to the RPi via the 40-Pin GPIO Connector. This section
describes in detail the devices located on the PI2AES-LITE .
4.1 PI2AES-LITE I2C BUS DEVICES
The following table describes the CPU I2C Bus usage of the PI2AES-LITE . 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-LITE I2C Bus Devices
4.1 WM8804 SPDIF TRANSMITTER
At the core of the PI2AES-LITE 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-LITE 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 3.3V TO 5V BUFFER
A 74HCT125 Quad Buffer is used to drive the WM8804 TXO output to the SPDIF (RCA)
and AES (Coax) Transfoerms and to the Toslink Optical Transmitter LED.

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5RPI
RPI RPI
RPI GPIO
GPIOGPIO
GPIO
5.1 OVERVIEW
The PI2AES-LITE 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-
LITE
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 Used to Generate Reset to the WM8804
18 - - - GPIO24 Unused
19 - - - GPIO10 Unused
20 - - - GND
21 - - - GPIO9 Unused

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RPi
PIN
DIR AF PUP/
PDN
PI2AES-
LITE
Name
Description/Notes
22 - - - GPIO25 Unused
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 Unused
30 - - - GND
31 OUT - PDN GPIO6 0 = Select 22.5792Mhz Clock Input to WM8804
1 = Select 24.5760Mhz 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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6PI2AES
PI2AESPI2AES
PI2AES-
--
-LITE
LITE LITE
LITE POWER
POWERPOWER
POWER
6.1 OVERVIEW
The PI2AES-LITE is designed to be powered from the Raspberry PI 5V GPIO Pins 2
and 4.

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7PI2AES
PI2AESPI2AES
PI2AES-
--
-LITE
LITE LITE
LITE SOFTWARE
SOFTWARESOFTWARE
SOFTWARE
7.1 OVERVIEW
Due to the various resources interfaced on the PI2AES-LITE , 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. For most Raspberry Pi Software, the HifiBerry
Digi+ Pro driver can be used.

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8CONNECTORS
CONNECTORSCONNECTORS
CONNECTORS
8.1 OVERVIEW
This section provides the type and location of the connectors on the PI2AES-LITE .
Table 5 – PI2AES-LITE Connector Locations

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9DOCUMENT REVISIONS
DOCUMENT REVISIONSDOCUMENT REVISIONS
DOCUMENT REVISIONS
Date Revision Change
09/04/2022 P2.0 Preliminary Release
Table 6 – Document Revisions

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1 ERRATA
ERRATAERRATA
ERRATA
10.1 OVERVIEW
The External 5V Option has been removed due to voltage drop issues. There is
currently no plan to fix.

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1111
11 CASE ASSEMBLY
CASE ASSEMBLYCASE ASSEMBLY
CASE ASSEMBLY
11.1 OVERVIEW
This section describes the Acrylic case included with the PI2AES-LITE and how to
assemble it for the PI 3 or PI 4.
11.2 PART DESCRIPTIONS
The acrylic case itself consist of 6 panels referred to as Bottom, Right, Left, Rear, Front
and Top. Note that the Left and Front are different for the PI 3 and PI 4.
Additionally, there is the following HW:
•M2.5 6mm Male-Female Standoff x 4
•M2.5 18mm Male-Female Standoff x 4
•M2.5 30mm Female-Female Standoff x4
•M2.5 6mm Panhead Phillips Screw x 9 (1 extra in case it runs away!)
The following photo shows these parts as well as the PI2AES-LITE.

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Figure 2 - PI2AES-LITE Acrylic Case Parts
TOP
BOTTOM
RIGHT
LEFT
FRONT
REAR
6MM
M
-
F
18MM
M
-
F
30MM
F
-
F
M2.5
SCREW

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11.3 ASSEMBLY STEP 1
Attach the 30mm F-F standoffs to the PI using the 6mm M-F to hold them as shown in
the following picture.

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11.4 ASSEMBLY STEP 2
Attach the bottom panel to the 6mm M-F standoffs as shown in the following picture.
Note the orientation of the SD Card cutout.

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11.5 ASSEMBLY STEP 3
Attach the PI2AES-LITE to the Raspberry Pi as shown in the following picture.