Audio Output Device example

[#1]

Description

This example implements an audio interface class device mode device that enumerates as audio device (USB speakers) and sends the samples sent to it from the host to the audio circuitry on the board.

Compiler build configurations

The software that makes up this example is designed to run on many different development boards. Therefore the compiler must be configured to build an image that is targeted to the development board you are using. This section explains how to set these build configurations for each of the supported compilers.

NOTE: read the Design notes section below if you are running this example on a part that supports high speed controllers.

LPCXpresso IDE

Configure projects

  right click on the BSP project in the project explorer window
  click Build Configurations->Set Active->(see configuration in table below)
  repeat these steps with the CDL, nxpUSBlib, and Example_AudioOutputDevice

Configure MCU

  right click on the Example_AudioOutputDevice project in the project explorer window
  click Properties->C/C++ Build->MCU settings->(see configuration in table below)

Configure the indexer

   click Window->Preferences->C/C++->Indexer->Use active build configuration

	BSP	CDL	nxpUSBlib	Example_AudioOutputDevice	MCU
LPC1850  / Hitex	LPC18xx_HITEX	LPC18xx	LPC18xx_Device	LPC18xx	LPC1850
LPC4330  / Xplorer	LPC4330_Xplorer	LPC18xx	LPC18xx_Device	LPC18xx	LPC4330
LPC4350  / Element14	LPC1435_ELEMENT14	LPC18xx	LPC18xx_Device	LPC18xx	LPC4350

NOTE: The LPC18xx CDL is used with boards that hold LPC43xx parts. This is done because the LPC43xx CDL is currently experimental. The LPC18xx USB library is used because both parts share the same controller.

Keil uVision 4 IDE

Configure a Batch Build

  click on Project->Batch Build...
  expand the BSP project to display a list of project targets
  select the project target by checking the appropriate checkbox (see target list in table below)
  repeat these steps with the CDL, nxpUSBlib_Device, and Example_AudioOutputDevice

	BSP	CDL	nxpUSBlib_Device	Example_AudioOutputDevice
LPC1850  / Hitex	HITEX1800	LPC18xx	LPC18xx_Device	HITEX1800

Board connections and configurations

LPC18xx_HITEX (LPC1850 Hitex Evaluation Board)  older A2 design

schematic ./BSP/schematics/HITEX_SCM_LPC1850EVA-A2-2.pdf

Connect the JTAG to the 20 pin receptacle marked X4 JTAG
Connect the type-B end of a USB cable to the receptacle marked X2. Plug the type-A end of this cable into a PC
Connect the mini-phono plug on a pair of headphones to the receptacle marked HP

LPC18xx_HITEX (LPC1850 Hitex Evaluation Board)  newer A4 design

schematic ./BSP/schematics/HITEX_Final_LPC1850EVA-A3.pdf

LPC4330_Xplorer (NGX Xplorer Evaluation Board with LPC4330)

Connect the JTAG to the 10 pin receptacle marked J2
Connect the micro-b end of a USB cable to the receptacle marked USB0. Plug the type-A end of this cable into a PC
Connect the mini-phono plug on a pair of headphones to the receptacle marked J5

LPC1435_ELEMENT14 (Element 14 gaming board with LPC4350)

Connect the JTAG to the 10 pin receptacle marked J6
Connect one end of a type-A to type-A USB cable to the receptacle marked USB0. Plug the other end of this cable into a PC
Connect the mini-phono plug on a pair of headphones to the receptacle marked J1

PC configuration

Use a PC running Windows XP, Vista or 7
Connect the type-A end of the USB cable that is connected to the board into one of the USB receptacles on the PC

Build and debug the example

LPCXpresso IDE

In the project explorer window of the IDE right click on the Example_AudioOutputDevice project and select Debug As->C/C++ MCU Application
In the main window of the IDE click Run->Resume to start running the application

Keil uVision 4 IDE

In the Batch Build window, select the project targets as described in Compiler Build Configurations and then click Build
In the main window of the IDE click Debug->Start/Stop Debug Session click Debug->Run

How this example runs and what to look for

On the PC select Control Panel->Hardware and Sound->Sound
When the example is first run a new entry in the Sound dialog box will appear titled Speakers and have a description that reads "4-nxpUSBlib Audio Out Demo". Below this description should be the word Ready.

To test the audio output click on this entry in the Sound dialog box. Then click on the Configure button to bring up the Speaker Setup dialog box. In this box press the Test button. Sound should be played through the left side of your headphones first, then the right side.

Design notes

This example is designed to run only at full speed. The nxpUSBlib runs the USB controllers on the LPC18xx and LPC43xx parts at high speed by default. This default must be changed to run this example properly on these parts. To do this, change the value of the definition USB_FORCED_FULLSPEED in the file libraries/nxpusblib/nxpUSBlibConfig.h to 1