BfAudio

intro

this page is my notes on getting audio working on the BF537-EZKIT LITE.

the EZKIT LITE has a AD1854 DAC which will work with the AD1836 driver in I2S mode. The DAC is attached to SPORT0 and uses SPI_SSEL4.

Setup audio selection switch to enable the output

• Set to all on for testing

4 Sept 2006

The static that can be controlled is related to SW7-6 and 7 (loopback to ADC). turning off SW7-6,7, or 8 eliminates all audio output.

Now for seemingly no reason audio works. i'm not going to complain... It works with SW7 all ON - again this may be due to the fact that my current EZKIT was modified by ADI more likely it's because ALSA is a pain to setup. if i turn off SW7-6,7 or 8 then the audio is disabled. Turning off SW7-1 helps with the noise because it disables the ADC data line (DR0PRI)

running audio_test seemed to help. it seems to have loaded modules:

root:~> lsmod
Module                  Size  Used by
snd_pcm_oss 39524 0 - Live 0x03260000
snd_mixer_oss 13124 1 snd_pcm_oss, Live 0x03054000

tone also seemed to load these modules but i couldn't load them by hand ( modprobe snd_pcm_oss). i would want to double check this before swearing to it. note that i do have autoload modules in my kernel config.

now tone and mp3play both work. i still get a lot of static on the output at times when there is nothing playing. at present i assume that this is noise from the ADC. I know the modification to this board has to do with the ADC being DC filtered (AC coupled) and that functionality has probably been removed. having SW7 all on ties the ADC and DAC together (sorta).

Kernel Config - Sound Section

<*> Advanced Linux Sound Architecture
<M>   Sequencer support 
<M>     Sequencer dummy client  
<M>   OSS Mixer API 
<M>   OSS PCM (digital audio) API 
[*]   OSS Sequencer API 
[ ]   Dynamic device file minor numbers (EXPERIMENTAL) 
[ ]   Support old ALSA API  

ALSA Blackfin Devices

<*> 1836 Audio support for BF53x    
     Interface between Blackfin and ADI1836 (I2S interface)  --->      
(0) Blackfin Audio SPORT port      
(4) Blackfin Audio SPI channel selection bit    
< > AD73311L Audio support for BF53x  

note - use the 1836 driver with the I2S interface, SPORT0 and SPI_SSEL4

31 Aug 2006

So far no real luck getting audio working. I am able to control the static a bit with 'tone'. A 1kHz sine wave doesn't really effect that static but a 20kHz wave silences it. I suspect the hardware as this board was modified by ADI for another project and I haven't looked into what they did. Also I need to check the audio selector switch to ensure output is enabled.

-- ChristopherPepe - 01 Sep 2006