Hello, thanks very much!

At the end we are making our USB Device an USB Audio Class Compliant ... but now we have some questions...

- Can I use my USB Device (USB Audio Class Compliant) with winmm.dll? If not... Which DLL should I use for that porpouse?

I've controlled my soundcard with this DLL, but I don't know if I could access to the driver USBAudio.sys... In fact, I only know "winmm.dll", but I expect that WDM Audio Drivers are a lot of things...

this is my example (partial):

private const string mmdll = "winmm.dll";

// native calls

[DllImport(mmdll)]

public static extern int waveOutWrite(IntPtr hWaveOut, ref WaveHdr lpWaveOutHdr, int uSize);

[DllImport(mmdll)]

public 
static extern int waveOutOpen(out IntPtr hWaveOut, int uDeviceID, WaveFormat lpFormat, WaveDelegate dwCallback, int dwInstance, int dwFlags);

[DllImport(mmdll)]

public static 
extern int waveOutReset(IntPtr hWaveOut);

...

And my program use these functions.

Can I use this functions to control my USB Audio Device?

Could anyone send me an example of USB Audio programming with C# (ó C++)?

Thanks in advance!

---

From:  DJ Sisolak <dsisolak@xxxxxxxxxxxxxxxxxxxxxx>
Reply-To:  wdmaudiodev@xxxxxxxxxxxxx
To:  "wdmaudiodev@xxxxxxxxxxxxx" <wdmaudiodev@xxxxxxxxxxxxx>
Subject:  [wdmaudiodev] Re: Building an USB audio interface with a PIC18F4550
Date:  Tue, 27 Mar 2007 16:53:59 -0700
>Hi All,
>
>Answers dispersed below...
>
>Thx,
>DJ Sisolak
>Microsoft Corp
>
>-----Original Message-----
>From: wdmaudiodev-bounce@xxxxxxxxxxxxx [mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Tim Roberts
>Sent: Monday, March 26, 2007 10:56 AM
>To: wdmaudiodev@xxxxxxxxxxxxx
>Subject: [wdmaudiodev] Re: Building an USB audio interface with a PIC18F4550
>
>Elios Elios Elios wrote:
> >
> > I'm making my end of career project (telecomunications engineering),
> > that consist in a USB interface for capturing audio by 4 channels. We
> > are using as IC the PIC18F4550 of Microchip. We have made the PCB, and
> > we have comunicated the PIC and the PC with an C# example that we have
> > found in the WEB. This example is for low speed, and for audio isn't
> > very good...
>
>To do 44.1kHz audio at 16 bits per sample with 4 channels takes 353
>kB/sec.  That's double what a low-speed device can do.  You'll need full
>speed.
>
>[DJ Sisolak] Correct, all spec compliant USB Audio devices MUST be full speed.
>
> > So, what is the better way to make an USB Audio Interface?
> >
> > I read the "USB Device Class Definition for Audio Devices 1.0" and the
> > 2.0... I think that if we follow the specification, we could to
> > control the interface with the driver Usbaudio.sys and programme it
> > with an Native API like WDMAudio Driver (winmm.dll, isn't?), or Core
> > Audio ...
>
>Yes, the best way to build an audio device is to meet the USB Audio
>Class Spec, as you describe above.  The trickiest part is creating the
>descriptors to describe your architecture, and even that's not too hard;
>there are samples in the documents on the USB web site.  You will want
>to do your streaming with an isochronous pipe.
>
>[DJ Sisolak] Again, correct. Streaming for USB Audio per the spec (MIDI being the exception) is done via Isochronous pipes. Descriptor generation for USB Audio 1.0 device is pretty straight forward from the spec. You may want to look at the guidelines as posted on http://www.microsoft.com/whdc/device/audio/UAA_HWdesign.mspx for some other information on this.
>
> > I read that there is a problem with USB 2.0 (the PIC18F4550 works in
> > USB 2.0, full speed) and Usbaudio.sys... Somebody knows it?
>
>Not that I know of.  There are a few discussions of this on the
>Microchip web site, but nothing negative.
>
>[DJ Sisolak] Full speed USB Audio devices should work just fine with USB 2.0 bus. There are some issues for getting a High Speed USB Audio 1.0 devices to work though.
>
>
> > Maybe the other solution can be to make a driver with Windriver... I
> > have listened that is very easy to do. But in this way only we could
> > to control our interface with our own driver... isn't?
>
>Making a simple driver with WinDriver might be easy, but making an audio
>driver of any kind is not easy.  Unless you run into some very serious
>problem, you should strive to make your device USB Audio Class compliant.
>
>[DJ Sisolak] I heartily agree. If for some reason you feel that the usbaudio.sys class driver does not fit your needs feel free to let me know why.
>
>--
>Tim Roberts, timr@xxxxxxxxx
>Providenza & Boekelheide, Inc.
>
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