{"id":1084,"date":"2017-09-18T13:57:43","date_gmt":"2017-09-18T11:57:43","guid":{"rendered":"http:\/\/www.fabienm.eu\/wordpress\/?p=1084"},"modified":"2017-09-30T11:10:15","modified_gmt":"2017-09-30T09:10:15","slug":"analog-input-with-usb-soundcard-on-linux-part1","status":"publish","type":"post","link":"https:\/\/www.fabienm.eu\/wordpress\/2017\/09\/18\/analog-input-with-usb-soundcard-on-linux-part1\/","title":{"rendered":"Analog input with usb soundcard on Linux [Part1]"},"content":{"rendered":"

I recently bought a current sensor to measure my electric house consumption. This sensor <\/a>as a 1 volt amplitude output signal that can be captured by a simple sound input.<\/p>\n

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Current curve on my kettle consumption captured by the sensor. Using a 10k resistor on output<\/p><\/div>\n

I don’t have microphone input on my raspberry pi 3. Then to use my sensor I had to buy an USB soundcard<\/a> on the internet.<\/p>\n

On my laptop (debian stretch), the usb-key is correctly seen as a sound-card :<\/p>\n

$ sudo dmesg\r\n[ 9474.556786] usb 1-1.2: new full-speed USB device number 5 using ehci-pci\r\n[ 9474.668021] usb 1-1.2: New USB device found, idVendor=8086, idProduct=0808\r\n[ 9474.668026] usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=0\r\n[ 9474.668028] usb 1-1.2: Product: USB PnP Sound Device\r\n[ 9474.668029] usb 1-1.2: Manufacturer: C-Media Electronics Inc.\r\n[ 9474.758118] hidraw: raw HID events driver (C) Jiri Kosina\r\n[ 9474.767742] usbcore: registered new interface driver snd-usb-audio\r\n[ 9474.771791] usbcore: registered new interface driver usbhid\r\n[ 9474.771793] usbhid: USB HID core driver\r\n[ 9474.778747] input: C-Media Electronics Inc. USB PnP Sound Device as \/devices\/pci0000:00\/0000:00:1a.0\/usb1\/1-1\/1-1.2\/1-1.2:1.3\/0003:8086:0808.0001\/input\/input19\r\n[ 9474.837031] hid-generic 0003:8086:0808.0001: input,hidraw0: USB HID v1.00 Device [C-Media Electronics Inc. USB PnP Sound Device] on usb-0000:00:1a.0-1.2\/input3\r\n<\/pre>\n
And works same on raspberrypi3 (with raspbian) :<\/p>\n
[171165.501265] usb 1-1.2: new full-speed USB device number 4 using dwc_otg\r\n[171165.609589] usb 1-1.2: New USB device found, idVendor=8086, idProduct=0808\r\n[171165.609608] usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=0\r\n[171165.609621] usb 1-1.2: Product: USB PnP Sound Device\r\n[171165.609634] usb 1-1.2: Manufacturer: C-Media Electronics Inc.      \r\n[171165.618168] input: C-Media Electronics Inc.       USB PnP Sound Device as \/devices\/platform\/soc\/3f980000.usb\/usb1\/1-1\/1-1.2\/1-1.2:1.3\/0003:8086:0808.0001\/input\/input0\r\n[171165.671634] hid-generic 0003:8086:0808.0001: input,hidraw0: USB HID v1.00 Device [C-Media Electronics Inc.       USB PnP Sound Device] on usb-3f980000.usb-1.2\/input3\r\n[171165.766026] usbcore: registered new interface driver snd-usb-audio\r\n<\/pre>\n
And seems to be correctly recognized by arecord<\/a> on raspberrypi3 :<\/p>\n
pi@raspberrypi:~ $ arecord -l\r\n**** List of CAPTURE Hardware Devices ****\r\ncard 1: Device [USB PnP Sound Device], device 0: USB Audio [USB Audio]\r\n  Subdevices: 1\/1\r\n  Subdevice #0: subdevice #0\r\n<\/pre>\n
And on my laptop !<\/p>\n
$ arecord -l\r\n**** List of CAPTURE Hardware Devices ****\r\ncard 0: PCH [HDA Intel PCH], device 0: ALC3202 Analog [ALC3202 Analog]\r\n  Subdevices: 0\/1\r\n  Subdevice #0: subdevice #0\r\ncard 1: Device [USB PnP Sound Device], device 0: USB Audio [USB Audio]\r\n  Subdevices: 0\/1\r\n  Subdevice #0: subdevice #0\r\n<\/pre>\n
With -L option :<\/p>\n
$ arecord -L\r\ndefault\r\n    Playback\/recording through the PulseAudio sound server\r\nnull\r\n    Discard all samples (playback) or generate zero samples (capture)\r\nsysdefault:CARD=PCH\r\n    HDA Intel PCH, ALC3202 Analog\r\n    Default Audio Device\r\nfront:CARD=PCH,DEV=0\r\n    HDA Intel PCH, ALC3202 Analog\r\n    Front speakers\r\ndmix:CARD=PCH,DEV=0\r\n    HDA Intel PCH, ALC3202 Analog\r\n    Direct sample mixing device\r\ndsnoop:CARD=PCH,DEV=0\r\n    HDA Intel PCH, ALC3202 Analog\r\n    Direct sample snooping device\r\nhw:CARD=PCH,DEV=0\r\n    HDA Intel PCH, ALC3202 Analog\r\n    Direct hardware device without any conversions\r\nplughw:CARD=PCH,DEV=0\r\n    HDA Intel PCH, ALC3202 Analog\r\n    Hardware device with all software conversions\r\nsysdefault:CARD=Device\r\n    USB PnP Sound Device, USB Audio\r\n    Default Audio Device\r\nfront:CARD=Device,DEV=0\r\n    USB PnP Sound Device, USB Audio\r\n    Front speakers\r\nsurround21:CARD=Device,DEV=0\r\n    USB PnP Sound Device, USB Audio\r\n    2.1 Surround output to Front and Subwoofer speakers\r\nsurround40:CARD=Device,DEV=0\r\n    USB PnP Sound Device, USB Audio\r\n    4.0 Surround output to Front and Rear speakers\r\nsurround41:CARD=Device,DEV=0\r\n    USB PnP Sound Device, USB Audio\r\n    4.1 Surround output to Front, Rear and Subwoofer speakers\r\nsurround50:CARD=Device,DEV=0\r\n    USB PnP Sound Device, USB Audio\r\n    5.0 Surround output to Front, Center and Rear speakers\r\nsurround51:CARD=Device,DEV=0\r\n    USB PnP Sound Device, USB Audio\r\n    5.1 Surround output to Front, Center, Rear and Subwoofer speakers\r\nsurround71:CARD=Device,DEV=0\r\n    USB PnP Sound Device, USB Audio\r\n    7.1 Surround output to Front, Center, Side, Rear and Woofer speakers\r\niec958:CARD=Device,DEV=0\r\n    USB PnP Sound Device, USB Audio\r\n    IEC958 (S\/PDIF) Digital Audio Output\r\ndmix:CARD=Device,DEV=0\r\n    USB PnP Sound Device, USB Audio\r\n    Direct sample mixing device\r\ndsnoop:CARD=Device,DEV=0\r\n    USB PnP Sound Device, USB Audio\r\n    Direct sample snooping device\r\nhw:CARD=Device,DEV=0\r\n    USB PnP Sound Device, USB Audio\r\n    Direct hardware device without any conversions\r\nplughw:CARD=Device,DEV=0\r\n    USB PnP Sound Device, USB Audio\r\n    Hardware device with all software conversions\r\n\r\n<\/pre>\n
 <\/p>\n
To test it on my laptop I hacked an extension cord to have a wire loop and grip the current sensor. I then plugged a kettle on it to capture the electric current signal.<\/p>\n
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current loop measurement<\/p><\/div>\n
Then I made measurement with arecord :<\/p>\n
$ arecord -d 10 -f cd -D plughw:1 -t wav foobar.wav\r\nRecording WAVE 'foobar.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, Stereo\r\n<\/pre>\n
And eared the sound of my boiling water with play :<\/p>\n
[16:51:57]fabien@martonilp:~\r\n$ play foobar.wav\r\n\r\nfoobar.wav:\r\n\r\nFile Size: 1.76M Bit Rate: 1.41M\r\nEncoding: Signed PCM\r\nChannels: 2 @ 16-bit\r\nSamplerate: 44100Hz\r\nReplaygain: off\r\nDuration: 00:00:10.00\r\n\r\nIn:100% 00:00:10.00 [00:00:00.00] Out:441k [!=====|=====!] Hd:0.0 Clip:0\r\nDone.\r\n<\/pre>\n
Then I\u00a0can ear the sound of current boiling water :<\/p>\n\nhttp:\/\/www.fabienm.eu\/wordpress\/wp-content\/uploads\/2017\/09\/Mesure_bouilloire_1100W.wav<\/a><\/audio>\n
 <\/p>\n
In futur article<\/a> we will see how to calculate the current consumption of my kettle from this wave files.<\/p>\n
References:<\/p>\n