av/cmd/audio-player/looper/pi0.go

// +build pi0

/*
DESCRIPTION
  pi0.go defines an initialisation function for use when running on the
	Raspberry Pi 0.

AUTHORS
  Ella Pietraroia <ella@ausocean.org>
  Scott Barnard <scott@ausocean.org>
	Saxon Nelson-Milton <saxon@ausocean.org>

LICENSE
  Copyright (C) 2020 the Australian Ocean Lab (AusOcean)

  It is free software: you can redistribute it and/or modify them
  under the terms of the GNU General Public License as published by the
  Free Software Foundation, either version 3 of the License, or (at your
  option) any later version.

  It is distributed in the hope that it will be useful, but WITHOUT
  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
  for more details.

  You should have received a copy of the GNU General Public License
  in gpl.txt.  If not, see http://www.gnu.org/licenses.
*/

package main

import (
	"os/exec"
	"time"

	"bitbucket.org/ausocean/utils/logger"
)

const audioCmd = "play"

func initCommand(l *logger.Logger) {
	const (
		cardPath = "/usr/share/doc/audioInjector/asound.state.RCA.thru.test"
		retryDur = 5 * time.Second
		alsactl  = "alsactl"
	)

	// Make sure utility to set up sound card, alsactl, exists.
	checkPath(alsactl, l)

	// Set up sound card using alsactl.
	cmdInit := exec.Command(alsactl, "-f", cardPath, "restore")
	err := cmdInit.Run()
	for err != nil {
		l.Log(logger.Warning, "alsactl run failed, retrying...", "error", err)
		time.Sleep(retryDur)
		err = cmdInit.Run()
	}

	// Make sure utility to play audio exists.
	checkPath(audioCmd, l)
}