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Full Discussion: C++, std:ofstream, and controlling an amplifiers mute function
Top Forums Programming C++, std:ofstream, and controlling an amplifiers mute function Post 303029758 by Circuits on Thursday 31st of January 2019 03:18:29 PM
Old 01-31-2019
C++, std:ofstream, and controlling an amplifiers mute function
Recently, I updated the unit I am running applications on with a new CODEC and amplifier; the older parts are EOL. There was a bug with the old setup. For some reason, even when a tone was not being generated, you could hear a noise emanating from the speaker when the LCD brightness was on a higher setting.


In order to counteract that problem the Amplifiers mute function (standby for old amp) was toggled on and off before and after a tone was produced:


Code:
const char *const amplifierGPIO = "/sys/class/gpio/gpio107/value";

    void amplifierOn()
    {
      std::ofstream amp(amplifierGPIO);
      if (amp.is_open())
      {
        amp << "1";
        amp.close();
      }
    }

    void amplifierOff()
    {
      std::ofstream amp(amplifierGPIO);
      if (amp.is_open())
      {
        amp << "0";
        amp.close();
      }
     }

The problem is that now in order to get the same functionality to work with the new amplifier I have to surround the ofstream in sleep statments:


Code:
const char *const amplifierGPIO = "/sys/class/gpio/gpio107/value";

    void amplifierOn()
    {
      sleep(1);
      std::ofstream amp(amplifierGPIO);
      if (amp.is_open())
      {
        amp << "1";
        amp.close();
      }
      sleep(1);
    }

    void amplifierOff()
    {
      sleep(1):
      std::ofstream amp(amplifierGPIO);
      if (amp.is_open())
      {
        amp << "0";
        amp.close();
      }
      sleep(1);
     }

1) Any ideas about why this might be the case? I do not believe it's the mute function on the amplifier itself because outside of the application that uses this ofstream (inside the boot loader) I can play a song and toggle it on and off with the mute function, with no delay needed.


2) Is there another way (other than ofstream) of toggling the GPIO pin 107 from within my application?
 

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LEARN ABOUT NETBSD

uaudio

UAUDIO(4)						   BSD Kernel Interfaces Manual 						 UAUDIO(4)

NAME

     uaudio -- USB audio device driver

SYNOPSIS

     uaudio* at uhub?
     audio*  at audiobus?

DESCRIPTION

     The uaudio driver provides support for USB audio class devices.

     A USB audio device consists of a number of components: input terminals (e.g. USB digital input), output terminals (e.g.  speakers), and a
     number of units in between (e.g. volume control).	The following types of units are handled by the uaudio driver and are accessible via the
     mixer (see audio(4)) interface:
	mixer	      A mixer has a number of inputs and one output.  Each input has a control that determines its volume in the output.  The name
		      of the control is mixN-S, where N is a number that identifies which mixer it is and S which input.
	selector      A selector unit selects one of multiple audio sources such as mic-in and line-in.  The name of the control is
		      selN-S1S2S3..., where N is a number that identifies which selector unit it is and the sequence of Sn indicates candidate
		      units for the audio source.
	feature       A feature unit changes the sound in some way, like bass, treble, mute, or volume.  The name of the control is determined in
		      a heuristic way.	If the unit changes the sound to a speaker output terminal, the names of the controls may be out-
		      puts.speaker.bass, outputs.speaker.treble, outputs.speaker.mute, outputs.speaker, or likewise.
	processing    A processing unit does one of a number of audio processing functions (e.g., channel up-down mixing, Dolby ProLogic, or cho-
		      rus effects).  The name of the on-off control is proN.M-enable, where N is a number that identifies which processing unit it
		      is and M which kind.  Depending on the type of processing unit there may be other controls as well.
	extension     An extension unit performs some unspecified audio processing The name of the on-off control is extN-enable, where N is a
		      number that identifies which processing unit it is.

     For more information the USB Audio class specification is indispensable reading.

SEE ALSO

     audio(4), usb(4)

     USB Approved Class Specification Documents, http://www.usb.org/developers/devclass_docs/.

HISTORY

     The uaudio driver appeared in NetBSD 1.5.

BUGS

     There is no support for multiple-endpoints audio stream, adaptive recording, async playback, and TYPE-II/III formats.

     There is the possibility that a device has multiple mixer items which have the same name.

BSD
								September 20, 2011							       BSD
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