Automatic audio recording question...

Perhaps you could implement this as a shell script running as a daemon. You can output a log in real time which you could format nicely as a web page to do your monitoring. If I understand you correctly, and you don't have internet access, just hook the pi up to a home network to monitor status and control recording etc (e.g. control the script over ssh until you get some buttons working on the GPIO). If you're familiar with C at all, I recall it being pretty straight forward to control a C program over UART on the pi. You could, for example, run the C program as a daemon checking for UART input and when that input is detected, fork and call arecord.

Thanks - I briefly contemplated writing something in C... I may end up rewriting the python portions in C if I run into any limitations with a GPIO expander. I ended up doing the following (still working on it):

Added apache to the sudoers file (note: this device won't be internet-connected, though the Pi will be running as an ad-hoc access point, but this is not recommended for security reasons)

Created a few php files:

This is my start_recording script:

function run_in_background($command) {
  shell_exec('sudo bash -c "exec nohup setsid ' . $command . ' > /dev/null 2>&1 &"');
}

$filename = date('Y_m_d-H_i') . '.wav';
$arecord = '/usr/bin/arecord -Dhw:0 -r 44100 -c 2 -f S16_LE /var/www/recordings/' . $filename;

// Run arecord in background
run_in_background($arecord);

$python = 'sudo python /home/pi/Adafruit_Python_SSD1306/examples/monitor_recordings.py';

// Run python in the backgroun
run_in_background($python);

By running shell_exec like above, arecord won't 'lock' the php page up from exiting.

I also have a stop_recording script:

exec('ps aux | grep \'^root.\{1,\}arecord\' | perl -pe \'$_ = join(",", split /\s+/, $_, 11)\'', $output);


foreach ($output as $value) {
  $temp_arr = str_getcsv($value);
  shell_exec('sudo kill -s SIGINT ' . $temp_arr[1]);
}




exec('ps aux | grep \'^root.\{1,\}monitor_recordings\' | perl -pe \'$_ = join(",", split /\s+/, $_, 11)\'', $output);


foreach ($output as $value) {
  $temp_arr = str_getcsv($value);
  shell_exec('sudo kill -s SIGINT ' . $temp_arr[1]);
}


shell_exec('sudo python /home/pi/Adafruit_Python_SSD1306/examples/clear.py');

The python code handles displaying recording metadata to an I2C connected OLED.

To handle the scheduling, I think I'll run a CRON job that curl's a php page that checks a MySQL DB and the status of arecord.

Very cool stuff. I appreciate you coming back posting an update of the status of your project as it provides me with ideas I had never thought of for a project of my own (I also see that you were further into details than I realized and I apologize for my vague response).

I'm working on a similar project trying to tie in with Musicbrainz to pull metadata to add to the recordings (Youtube, Pandora, internet radio, vinyl, cassette etc.).

I have a few questions of curiosity:

If you don't mind me asking, what source are you recording?

What sort of data are you outputting to the OLED? Output from arecord?

Also, from what I gather the recordings are all to kick off and end at a certain time based on your scheduling data. Is that correct?

If you don't mind me asking, what source are you recording?

Sermons during mass. I was unable to find a schedulable recorder under $2000, though maybe something exists that I missed. I toyed with the idea of using a security system DVR, but didn't see any units that I liked.

What sort of data are you outputting to the OLED? Output from arecord?

Right now:

REC

Filename.wav

Time: mm:ss

arecord pid (debugging purposes)

Eventually I'll make a bar that shows how much disk space is used / free.

Also, from what I gather the recordings are all to kick off and end at a certain time based on your scheduling data. Is that correct?

Yes.

Now that I have this part worked out, I need to add a USB jump drive. My ultimate goal is to have the SD be read only, and have it do all audio writes to a USB drive.

John

http://www.element14.com/community/thread-branch!input.jspa?message=123463