Liam,
OMAP4 DMIC only works on 2 channels but 4 or 6 channels by means of arecord and ABE diagram.
1. "arecord -f dat -c 4 plughw:0,0 dmic-4.wav" returns
Recording WAVE 'dmic-4.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Channe[ 929.988220] omap-dmic-dai omap-dmic-dai: is ls 4 [ 929.996002] asoc: interface omap-dmic-abe-dai-0 hw params failed [ 930.002563] SDP4430 Media: omap_abe_dai_hw_params: backend hw_params failed -22 [ 930.011016] asoc: interface MultiMedia1 hw params failed arecord: set_params:1116: Unable to install hw params: ACCESS: RW_INTERLEAVED FORMAT: S16_LE SUBFORMAT: STD SAMPLE_BITS: 16 FRAME_BITS: 64 CHANNELS: 4 RATE: 48000 PERIOD_TIME: 42625 PERIOD_SIZE: 2046 PERIOD_BYTES: 16368 PERIODS: 4 BUFFER_TIME: 170500 BUFFER_SIZE: 8184 BUFFER_BYTES: 65472 TICK_TIME: 0
2. "arecord -f dat -c 2 plughw:0,0 dmic-4.wav" collects wrong data, no voice is capture in dmic-4.wav. if following is set. amixer cset numid=58 4 amixer cset numid=59 3 amixer cset numid=60 2 amixer cset numid=61 1
item 1 indicates DMIC refuses to take more than 2 channels using arecord. item 2 indicates DMIC capture no voice data if 2 DMIC pins (4 channels) are enabled and arecord using 2 channels.
amixer does not handle any channel number. And ABE does not overwrite number of channels set by arecord.
Do you think it is bug?
Thanks.
---henry