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Support for Botic Linux driver

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M

miero

Member
Joined 2011
After 2 months and 2 days updated Botic driver (v3) is OUT!

http://bbb.ieero.com/

Notice:
- changed default pins for data2 from P9_28 to P9_42 (but it can be switched back easily )
- compatible with Botic cape (however not tested yet)
- changed configuration of channels (see README)
- added possibility to output SPDIF streams (four of them)
- underruns should be fixed now (with playing on real-time priority)
- from command line use "chrt 1 play ... " to play with real-time priority
- BBB overclocked to 1GHz by default
- interrupt handler for mcasp (detects HW errors and resumes halted playback in worst case)
- updated MPD with DSD and realtime patches (provided by lintweaker - many thanks!)

Known issues:
- playback of 384kHz works in 50% cases

Enjoy!
 
Last edited:
D

dabrain

Member
Joined 2014
Hello,

I'm really interested by this thread because i would like to support DSD on an Imx6 with WM8741 DAC. As i read previously, it seems to be possible with the botic driver to support wm8741. I just wanted to discuss with you on what i need concerning imx6 or another SOC. As I understood, you are using a GPIO to send the DSD data but what caps do i need to do that on imx6? I'm checking in the meanwhile to sort out the information...:)
 
L

linuxfan

Member
Joined 2007
Miero, thanks for these refinements.
miero said:
- BBB overclocked to 1GHz by default
Click to expand...
I like to know the underlying settings - are you just using these 2 commands at bootup?
Code: 
cpufreq-set -g userspace
cpufreq-set -f 1000Mhz
Also, do you find that with the BBB locked to 1000Mhz that it gets warm/hot?
If so, do you think we should add a small heatsink to the Sitara processor?
Thanks
 
D

dabrain

Member
Joined 2014
Hello Miero,

After reading code and datasheet, i would to clarify some points. Indeed the imx6 give acces to a synchronous serial interface SSI which allow to communicate with different kind of serial devices. Thats the way today i'm communicating with a wm8740 in I2S. In your DSD solution, i understand that you are using a fake PCM mode in ALSA to send DSD data and so I'm wondering about the burst transfer mode. Why do I need this mode to transfer DSD ?
Is it a kind of I2S msasp mode subset ?
For now i'm sorry if i ask stupid questions but i'm trying to sort out what do I need on my chip to perform what you did with mcASP.
Best regards.
 
M

miero

Member
Joined 2011
Good question dabrain. The I2S is subset of TDM (Time Division Multiplex) which combines multiple channels (e.g. left+right channel) into single stream. For DSD_U8 you need two streams (stereo) with single channel in the each. So you need to setup TDM to 1 channel in stream (i.e. no multiplex), but this is not valid configuration option in McASP. However the McASP supports setting number 0 into that register, which is the (non-periodic) Burst mode but for DSD it is used periodically.

Another option is to use DSD_U16_LE bit format which can be played as 4ch 16bit PCM but you need to adapt something (ALSA or player) to reorder bytes in DSD stream.
 
D

dabrain

Member
Joined 2014
Thx a lot miero. I just purchased a beaglebone black to perform some tests against your distribution. But i'm not able to launch the DSD playback. I'm getting this error.

Failed to open mixer for 'Botic'

Do I need to have ES9018 plugged in ? Or can i just get the signal out from the dedicated pins ? Do i need to change a setting to support the dsd files included in the distrib ?
Best regards.

Steph
 
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