hi, it looks like your ADC is working in TDM mode and not really I2S (the wires are the same but the frames are different as you can see..).
AFAIK the A10/A20 looks like (from datasheets) not being capable to do TDM; instead other Allwinner SOCs like H3 shoud be HW-wise capable. never check if the kernel driver is suitable anyway. your kernel, then, is my second remark.. it looks like you are talking about the "legacy kernel 3.4", from Allwinner "BSP", but here i suppose you'll find more skills on mainlinux 4.x from linux-sunxi.org where there's active development for an I2S driver. anyway it's your choice to evaluate and decide if stay with legacy or move on mainline. i can understand that if this is your first approach to linux kernel world, things could look like pretty "cloudy".. :-) have fun! Il giorno venerdì 20 ottobre 2017 10:36:53 UTC+2, [email protected] ha scritto: > > Hi, > > I'm new in this group and also pretty new with Linux, so I hope you have > patience we me if I'm asking stupid questions, > I'm currently working with an Olimex A20 Lime2 board, trying to interface > an 24 bit ADC (AD7768 from Analog Devices) > to the I2S interface. > > So far I have done the following: > > 1. I have the following drivers built into the kernel: > sunxi-i2s.ko > sunxi-i2sdma.ko > sndi2s.ko > sunxi-i2s.ko > > 2. The I2S interface also appears as an ALSA hardware device (#sudo > arecord -l) > I have briefly tested it without anything electrically connected to it, > using arecord and an oscilloscope, observing how for instance > LRCLK changes frequency when i change the sampling frequency in the call > to arecord. > > 3. AD7768 is an 8 channel 24bit ADC. It works in I2S master mode, so I > have configured my A20 as slave (I have updated the fex file). > The ADC outputs data from all channels in an interleaved manner, > 32bits/channel, on the same data line (I2S_DI). > Timing looks something like the following (one LRCLK data strobe per 8 > channels of data): > > _ > > _ > LRCLK: _| > |__________________________________________________________________| > |______________ > > > DIN: --< CH1 >< CH2 >< CH3 >< CH4 >< CH5 >< CH6 >< CH7 >< CH8 > >------------------------< CH1 >< CH2 >... > > > 6. I have written a small c code that uses the alsa/asound library to > interface the ADC. > My problem is that the sunxi I2S drivers only seems to support S16_LE and > S24_LE format and furthermore only up to 2 channels. > Given the timing above I think I'll need S32_LE and 8 channels. > > 7. My guess (please correct me I'm wrong) is that I need to update the I2S > drivers to accomplish this. > Being new to Linux and especially on Linux drivers, I really don't know > where to start. > I have looked into the source code of sunxi-i2s, sunxi-i2sdma, sndi2s and > sunxi-i2s and at least three of them have settings regarding > bit format and number of channels, should I change them all? > > 8. Furthermore I have looked into the Allwinner A20 manual and in this > it's stated that the I2S interface supports 16, 20 and 24 bits resolution, > so I'm not even sure that A20 supports 32 bit data words. > > > Grateful for any suggestions. > > Regards > Per > -- You received this message because you are subscribed to the Google Groups "linux-sunxi" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
