XMOS xCORE-200 Multi-channel Audio board Guide

USB Audio Design Guide
Document Number: XM0088546.1
Publication Date: 2016/5/12
XMOS © 2016, All Rights Reserved.

USB Audio Design Guide 2/110
SYNOPSIS
The XMOS USB Audio solution provides USB Audio Class compliant devices over USB 2.0 (high-
speed or full-speed). Based on the XMOS XS1 architecture, it supports USB Audio Class 2.0 and
USB Audio Class 1.0, asynchronous mode and sample rates up to 384kHz.
The complete source code, together with the free XMOS xTIMEcomposer development tools
and XCORE multi-core micro-controller devices allow the implementer to select the exact mix of
interfaces and processing required.
The XMOS USB Audio solution is deployed as a framework with reference design applications
extending and customising this framework. These reference designs have particular qualified
feature sets and an accompanying reference hardware platform.
This software design guide assumes the reader is familiar with the XC language and xCORE devices.
For more information see XMOS Programming Guide1.
The reader should also familiarise themselves with the XMOS USB Device Library
2
and the XMOS
USB Device Design Guide3
The reader should always refer to the supplied CHANGELOG and README files for known issues
etc in a specific release
1https://www.xmos.com/published/xmos-programming-guide
2http://www.xmos.com/published/xuddg
3https://www.xmos.com/zh/node/17007?page=9
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Table of Contents
1 Overview 5
2 Hardware Platforms 6
2.1 xCORE-200 Multi-Channel Audio Board ......................... 6
2.1.1 Analogue Input & Output .............................. 7
2.1.2 Digital Input & Output ................................ 7
2.1.3 MIDI ........................................... 7
2.1.4 Audio Clocking .................................... 7
2.1.5 LEDs, Buttons and Other IO ............................. 7
2.2 xCORE-200 Microphone Array Board ........................... 8
2.2.1 Microphones ...................................... 9
2.2.2 Analogue Output ................................... 9
2.2.3 Audio Clocking .................................... 10
2.2.4 Buttons, LEDs and Other IO ............................. 10
2.3 USB Multi-function Audio (MFA) Kit ............................ 12
2.4 U16 Multi-Channel USB Audio Kit ............................. 13
2.5 USB Audio 2.0 DJ Kit .................................... 14
2.6 USB Audio 2.0 Reference Design Board ......................... 14
2.7 USB Audio 2.0 Multichannel Reference Design Board ................. 15
3 Software Architecture 17
3.1 The USB Audio System Architecture ........................... 18
3.2 XMOS USB Device (XUD) Library .............................. 18
3.3 Endpoint 0: Management and Control .......................... 20
3.3.1 Enumeration ...................................... 20
3.3.2 Over-riding Standard Requests ........................... 21
3.3.3 Class Requests .................................... 21
3.4 Audio Endpoints (Endpoint Buffer and Decoupler) ................... 22
3.4.1 Endpoint Buffer .................................... 22
3.4.2 Decoupler ....................................... 23
3.4.3 Audio Buffering Scheme ............................... 23
3.4.4 Decoupler/Audio Core interaction ......................... 23
3.5 Audio Driver ......................................... 25
3.5.1 Port Configuration (xCORE Master) ......................... 27
3.5.2 Changing Audio Sample Frequency ......................... 28
3.6 Digital Mixer ......................................... 28
3.6.1 Control ......................................... 29
3.6.2 Host Control ...................................... 29
3.7 S/PDIF Transmit ....................................... 31
3.7.1 Clocking ........................................ 32
3.7.2 Usage .......................................... 33
3.7.3 Output stream structure ............................... 33
3.8 S/PDIF Receive ........................................ 33
3.8.1 Usage and Integration ................................ 34
3.9 ADAT Receive ........................................ 35
3.9.1 Integration ....................................... 36
3.10 External Clock Recovery (ClockGen) ........................... 36
3.11 MIDI .............................................. 37
3.12 PDM Microphones ...................................... 37
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3.13 Overview of PDM implemention .............................. 37
3.13.1 PDM Microphone Hardware Characteristics .................... 38
3.13.2 Integration of PDM Microphones into USB Audio ................. 39
3.14 Resource Usage ....................................... 40
4 Features & Options 41
4.1 Device Firmware Upgrade (DFU) .............................. 41
4.2 USB Audio Class Version Support ............................. 41
4.2.1 Driver Support ..................................... 42
4.2.2 Audio Class 1.0 Mode and Fall-back ........................ 42
4.3 Audio Controls via Human Interface Device (HID) ................... 43
4.4 Apple MFi compatibility .................................. 44
4.5 Audio Stream Formats ................................... 44
4.5.1 Audio Subslot ..................................... 45
4.5.2 Audio Sample Resolution .............................. 45
4.5.3 Audio Format ..................................... 46
4.6 DSD over PCM (DoP) .................................... 46
5 Programming Guide 48
5.1 Getting Started ....................................... 48
5.1.1 Building and Running ................................. 48
5.1.2 Installing the application onto flash ........................ 49
5.2 Project Structure ...................................... 50
5.2.1 Applications and Modules .............................. 50
5.3 Build Configurations .................................... 50
5.4 Validated Build Configurations .............................. 51
5.5 Configuration Naming Scheme .............................. 51
5.6 A USB Audio Application .................................. 51
5.6.1 Custom Defines .................................... 52
5.6.2 Configuration Functions ............................... 53
5.6.3 The main program .................................. 55
5.7 Adding Custom Code .................................... 58
5.7.1 Example: Changing output format ......................... 59
5.7.2 Example: Adding DSP to output stream ...................... 59
6 USB Audio Applications 61
6.1 USB Audio 2.0 Reference Design (L-Series) Application ................ 61
6.1.1 Port 32A ........................................ 62
6.1.2 Clocking ........................................ 63
6.1.3 HID ........................................... 64
6.1.4 Validated Build Options ............................... 65
6.2 The USB Audio 2.0 DJ Kit (U-Series) ............................ 66
6.2.1 Clocking and Clock Selection ............................ 67
6.2.2 CODEC Configuration ................................. 67
6.2.3 U-Series ADC ...................................... 67
6.2.4 HID Example ...................................... 67
6.2.5 Validated Build Options ............................... 68
6.3 The USB Audio 2.0 Multichannel Reference Design (L-Series) Software ....... 69
6.3.1 Clocking ........................................ 71
6.3.2 Validated Build Options ............................... 71
6.4 The Multi-function Audio Kit (U-Series) .......................... 72
6.4.1 Clocking and Clock Selection ............................ 72
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6.4.2 DAC and ADC Configuration ............................. 73
6.4.3 U-Series ADC ...................................... 73
6.4.4 HID Example ...................................... 73
6.4.5 Validated Build Options ............................... 76
6.5 The U-Series Multi-Channel USB Audio Kit ........................ 77
6.5.1 Clocking and Clock Selection ............................ 77
6.5.2 DAC and ADC Configuration ............................. 78
6.5.3 AudioHwInit() ..................................... 78
6.5.4 AudioHwConfig() ................................... 78
6.5.5 Validated Build Options ............................... 79
6.6 The xCORE-200 Multi-Channel Audio Board ....................... 79
6.6.1 Clocking and Clock Selection ............................ 80
6.6.2 DAC and ADC Configuration ............................. 80
6.6.3 AudioHwInit() ..................................... 81
6.6.4 AudioHwConfig() ................................... 81
6.6.5 Validated Build Options ............................... 82
6.7 The xCORE-200 Array Microphone Board ........................ 82
6.7.1 Clocking and Clock Selection ............................ 83
6.7.2 DAC Configuration .................................. 84
6.7.3 AudioHwInit() ..................................... 84
6.7.4 AudioHwConfig() ................................... 84
6.7.5 Mic Processing Example ............................... 84
6.7.6 Validated Build Options ............................... 85
7 API 86
7.1 Configuration Defines ................................... 86
7.1.1 Code location (tile) .................................. 86
7.1.2 Channel Counts .................................... 87
7.1.3 Frequencies and Clocks ............................... 87
7.1.4 Audio Class ...................................... 88
7.1.5 System Feature Configuration ............................ 89
7.1.6 USB Device Configuration .............................. 91
7.1.7 Stream Formats .................................... 92
7.1.8 Volume Control .................................... 96
7.1.9 Mixing Parameters .................................. 97
7.1.10 Power .......................................... 98
7.2 Required User Function Definitions ............................ 98
7.2.1 External Audio Hardware Configuration Functions ................ 98
7.2.2 Audio Streaming Functions ............................. 99
7.2.3 Host Active ....................................... 99
7.2.4 HID Controls ......................................100
7.3 Component API .......................................100
8 Frequently Asked Questions 110
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1 Overview
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Functionality
Provides USB interface to audio I/O.
Supported Standards
USB USB 2.0 (Full-speed and High-speed)
USB Audio Class 1.04
USB Audio Class 2.05
USB Firmware Upgrade (DFU) 1.16
USB Midi Device Class 1.07
Audio I2S/TDM
S/PDIF
ADAT
Direct Stream Digital (DSD)
PDM Microphones
MIDI
Supported Sample Frequencies
44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz, 192kHz, 352.8kHz, 384kHz
Supported Devices
XMOS Devices xCORE-200 Series
XS1 L-Series
XS1 U-Series
XS1 G-Series (Not recommended for
new designs)
Requirements
Development Tools xTIMEcomposer Development Tools
v14 or later
USB External ULPI USB Phy (If using XS1
G/L-Series)
Audio External audio DAC/ADC/CODECs
(and required supporting
componentry) supporting I2S/TDM
Boot/Storage Compatible SPI Flash device
Licensing and Support
Reference code provided without charge under license from XMOS.
Please visit http://www.xmos.com/support/contact for support.
Reference code is maintained by XMOS Limited.
4http://www.usb.org/developers/devclass_docs/audio10.pdf
5http://www.usb.org/developers/devclass_docs/Audio2.0_final.zip
6http://www.usb.org/developers/devclass_docs/DFU_1.1.pdf
7http://www.usb.org/developers/devclass_docs/midi10.pdf
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2 Hardware Platforms
IN THIS CHAPTER
·xCORE-200 Multi-Channel Audio Board
·xCORE-200 Microphone Array Board
·USB Multi-function Audio (MFA) Kit
·U16 Multi-Channel USB Audio Kit
·USB Audio 2.0 DJ Kit
·USB Audio 2.0 Reference Design Board
·USB Audio 2.0 Multichannel Reference Design Board
The following sections describe the hardware platforms that support development
with the XMOS USB Audio software framework.
2.1 xCORE-200 Multi-Channel Audio Board
The XMOS xCORE-200 Multi-channel Audio board
8
(XK-AUDIO-216-MC) is a com-
plete hardware and reference software platform targeted at up to 32-channel USB
and networked audio applications, such as DJ decks and mixers.
The Multichannel Audio Platform hardware is based around the XE216-512-TQ128
multicore microcontroller; an dual-tile xCORE-200 device with an integrated High
Speed USB 2.0 PHY, RGMII (Gigabit Ethernet) interface and 16 logical cores deliver-
ing up to 2000MIPS of deterministic and responsive processing power.
Exploiting the flexible programmability of the xCORE-200 architecture, the Multi-
channel Audio Platform supports either USB or network audio source, streaming 8
analogue input and 8 analogue output audio channels simultaneously - at up to
192kHz. Ideal for mixing two sources and providing main and headphone monitor
output feeds.
For full details regarding the hardware please refer to xCORE-200 Multichannel
Audio Platform Hardware Manual9.
The reference board has an associated firmware application that uses the USB
Audio 2.0 software reference platform. Details of this application can be found in
section §6.6.
8https://www.xmos.com/support/boards?product=18334
9https://www.xmos.com/support/boards?product=18334&component=18687
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2.1.1 Analogue Input & Output
A total of eight single-ended analog input channels are provided via 3.5mm stereo
jacks. Each is fed into a CirrusLogic CS5368 ADC. Similarly a total of eight single-
ended analog output channels are provided. Each is fed into a CirrusLogic CS4384
DAC.
The four digital I2S/TDM input and output channels are mapped to the xCORE
input/outputs through a header array. The jumper allows channel selection when
the ADC/DAC is used in TDM mode
2.1.2 Digital Input & Output
Optical and coaxial digital audio transmitters are used to provide digital audio
input output in formats such as IEC60958 consumer mode (S/PDIF) and ADAT. The
output data streams from the xCORE-200 are re-clocked using the external master
clock to synchronise the data into the audio clock domain. This is achieved using
simple external D-type flip-flops.
2.1.3 MIDI
MIDI I/O is provided on the board via a standard Gameport connector. The signals
are buffered using 5V line drivers and are then connected to 1-bit ports on the
xCORE-200, via a 5V to 3.3V buffer.
2.1.4 Audio Clocking
A flexible clocking scheme is provided for both audio and other system services.
In order to accommodate a multitude of clocking options, the low-jitter master
clock is generated locally using a frequency multiplier PLL chip. The chip used is a
Phaselink PL611-01, which is pre-programmed to provide a 24MHz clock from its
CLK0 output, and either 24.576 MHz or 22.5792MHz from its CLK1 output.
The 24MHz fixed output is provided to the xCORE-200 device, as the main pro-
cessor clock. It also provides the reference clock to a Cirrus Logic CS2100, which
provides a very low jitter audio clock from a synchronisation signal provided from
the xCORE-200.
Either the locally generated clock (from the PL611) or the recovered low jitter clock
(from the CS2100) may be selected to clock the audio stages; the xCORE-200, the
ADC/DAC and Digital output stages.
2.1.5 LEDs, Buttons and Other IO
An array of 4*4 green LEDs, 3 buttons and a switch are provided for general
purpose user interfacing. The LED array is driven by eight signals each controlling
one of 4 rows and 4 columns.
A standard XMOS xSYS interface is provided to allow host debug of the board via
JTAG.
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2.2 xCORE-200 Microphone Array Board
The XMOS xCORE-200 Microphone Array board
10
(XK-USB-MIC-UF216) is design
available from XMOS based on a dual-tile XMOS xCORE-200 device.
The board integrates the following building blocks: multiple omni-directional
microphones, on-board low-jitter clock sources, configurable user input buttons
and a USB2.0 device for connectivity. making it an ideal platform for a range of
multichannel microphone aggregation products.
The board is powered by an XUF216-512 xCORE-200 multicore microcontroller.
This device has sixteen 32bit logical cores that deliver up to 2000MIPS completely
deterministically. In addition the XUF216 has powerful DSP properyies with native
32bit/64 instructions delivering up to 1000MMACS.
Figure 1shows the block layout of the xCORE-200 Microhone Array board.
xCORE
XUF216
Ethernet
PHY
LAN8710A
RJ45
25MHz
TILE CLK to xCore
DAC-MCLK
PLL CLK
Device
CS2100
BUFFERMCLK 24.576
MHz
SMI
MDI
DAC
CS43L21
MEMS mic
AKU441
I2S
I2C
HP
MII
USB
Type-B
1v3v3 2v5
XTAG(J2)
MIC0
MIC4
MIC3
MIC2
MIC1
MIC5
MIC6
MIC-DATA[6:0]
MIC-CLK
Buffer
MIC CLK[6:0]
JTAG
LEDs
BUFFER
PUSH BUTTON
D-FF
3.5mm Jack
USB diff pair
24MHz
Figure 1:
xCORE-200
Microphone
Array Board
Block
Diagram
For full details regarding the hardware please refer to xCORE Microphone Array
Hardware Manual11.
The reference board has an associated firmware application that uses the USB
Audio 2.0 software reference platform. Details of this application can be found in
section §6.7.
10https://www.xmos.com/support/boards?product=20258
11https://www.xmos.com/download/private/xCORE-Microphone-Array-Hardware-Manual%281v1%29.pdf
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