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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 FREEBSD

acpi_panasonic

ACPI_PANASONIC(4)					   BSD Kernel Interfaces Manual 					 ACPI_PANASONIC(4)

NAME

     acpi_panasonic -- ACPI hotkey driver for Panasonic laptops

SYNOPSIS

     To compile this driver into the kernel, place the following line in your kernel configuration file:

	   device acpi_panasonic

     Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):

	   acpi_panasonic_load="YES"

DESCRIPTION

     The acpi_panasonic driver enables such hotkey facilities of various Panasonic laptops as changing LCD brightness, controlling mixer volumes,
     entering sleep or suspended state and so on.  On the following models it is reported to work: Let's note (or Toughbook, outside Japan) CF-
     R1N, CF-R2A and CF-R3.  It may also work on other models as well.

     The driver consists of three functionalities.  The first is to detect hotkey events and take corresponding actions, which include changing
     LCD luminance and speaker mute state.  The second role is to notify occurrences of the event by way of devctl(4) and eventually to devd(8).
     The third and last is to provide a way to adjust LCD brightness and sound mute state via sysctl(8).

   Hotkeys
     There are 9 hotkeys available on the supported hardware:

	   Fn+F1       Make LCD backlight darker.
	   Fn+F2       Make LCD backlight brighter.
	   Fn+F3       Switch video output between LCD and CRT.  Not supported by the acpi_panasonic driver.
	   Fn+F4       Toggle muting the speaker.
	   Fn+F5       Turn the mixer volume down.
	   Fn+F6       Turn the mixer volume up.
	   Fn+F7       Enter suspend-to-RAM state.
	   Fn+F9       Show battery status.
	   Fn+F10      Enter suspend-to-disk state.

     Actions are automatically taken within the driver for Fn+F1, Fn+F2 and Fn+F4.  For the other events such as mixer control and showing battery
     status, devd(8) should take the role as described below.

   devd(8) Events
     When notified to devd(8), the hotkey event provides the following information:

	   system      "ACPI"
	   subsystem   "Panasonic"
	   type        The source of the event in ACPI namespace.  The value depends on the model but typically "\_SB_.HKEY".
	   notify      Event code (see below).

     Event codes to be generated are assigned as follows:

	   0x81-0x86, 0x89
		       Fn+F<n> pressed.  0x81 corresponds to Fn+F1, 0x82 corresponds to Fn+F2, and so on.

	   0x01-0x07, 0x09, 0x1a
		       Fn+F<n> released.  0x01 corresponds to Fn+F1, 0x02 corresponds to Fn+F2, and so on.

SYSCTL VARIABLES

     The following MIBs are available:

     hw.acpi.panasonic.lcd_brightness_max
	     The maximum level of brightness.  The value is read only and automatically set according to hardware model.

     hw.acpi.panasonic.lcd_brightness_min
	     The minimum level of brightness.  The value is read only and automatically set according to hardware model.

     hw.acpi.panasonic.lcd_brightness
	     Current brightness level of the LCD (read-write).	The value ranges from hw.acpi.panasonic.lcd_brightness_min to
	     hw.acpi.panasonic.lcd_brightness_max.

     hw.acpi.panasonic.sound_mute
	     A read-write boolean flag to control whether to mute the speaker.	The value 1 means to mute and 0 not.

SEE ALSO

     acpi(4), devd.conf(5), devd(8), sysctl(8)

HISTORY

     The acpi_panasonic driver first appeared in FreeBSD 5.3.

AUTHORS

     The acpi_panasonic driver and this manual page were written by OGAWA Takaya <t-ogawa@triaez.kaisei.org> and TAKAHASHI Yoshihiro
     <nyan@FreeBSD.org>.

BSD
								 February 25, 2012							       BSD
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