It will be a day or so, but I will post the write-up here. You will not be able to control the IC independently, since the kernel claims the device. The Linux audio system expects to be able to control the audio controls such as volume, etc. by reaching into the CODEC through the control bus. The kernel blocks direct user space access to the device.
In fact one way to make sure the device tree loaded correctly is that the "UU" symbol appears at the devices' I2C address. --- Graham == On Tuesday, May 16, 2017 at 10:51:19 AM UTC-5, ags wrote: > > I would appreciate the writeup, thank you. > > My project requires interfacing to an IC with I2S input. I planned on > using (something like) aplay to write audio out to I2S/McASP channel (using > built-in driver support) and hoped I could also use the built-in support > (drivers) for SPI and/or I2C using the /dev/spidev<x.y> or /dev/i2c-<n> > devices to control the IC. > > On Monday, May 15, 2017 at 6:46:50 PM UTC-7, Graham wrote: >> >> Yes, I was able to get a CircuitCo Rev.B Audio cape running, using the >> I2S/McASP interface. >> I'll write it up for you, if you are interested. >> >> If you are going to use a different CODEC or other device on the >> I2S/McASP interface, >> you will need to see if a driver already exists for it, or if it fits a >> generalized I2S audio interface that >> is already inside the kernel can be invoked and controlled from a device >> tree. >> >> If it is unique, then you will have to write your own Linux driver and >> recompile the kernel. >> >> If you just want audio, it is a lot easier to just use a USB CODEC. >> >> --- Graham >> >> == >> >> On Monday, May 15, 2017 at 6:11:11 PM UTC-5, ags wrote: >>> >>> I'm also interested as I have a project where I will interface directly >>> to the I2S/McASP interface. Did you figure it out? >>> >>> >>> On Tuesday, January 3, 2017 at 8:57:29 AM UTC-8, Graham wrote: >>>> >>>> I spent most of the weekend down in the rabbit-hole, trying to get a >>>> CircuitCo Rev_B Audio cape to work, (unsuccessfully.) >>>> >>>> Is this cape compatible-with / supported-by Debian 8.6/kernel 4.4 ? >>>> >>>> Does the BB-BONE-AUDI-02-00A0.dtbo overlay that comes with the current >>>> distribution work? >>>> >>>> How can you tell if an overlay actually loaded, with 4.4? >>>> /sys/devices/platform/bone_capemgr/slots >>>> as well as the boot log, only shows the first physical four, and no >>>> longer shows the higher numbered "pseudo-capes" and overlay status. >>>> >>>> I understand that >>>> The CircuitCo cape does not have an EEPROM, so everything needs to be >>>> configured explicitly. >>>> I need to use a base .dts with HDMI audio disabled, then load the >>>> overlay for the CircuitCo card. >>>> I also need to load the asound.state file. >>>> >>>> Am I approaching this correctly? >>>> >>>> I can not use a USB-soundcard for audio. I have several applications >>>> that need McASP/I2S running for several other codecs, but I thought I >>>> would start >>>> with the CircuitCo cape as a starting point. >>>> >>>> Thanks, >>>> --- Graham >>>> >>>> == >>>> >>>> -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/096b89d2-9856-47d2-b063-e8d5e9ff799f%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
