Re: DRAWS and Buster distro

Basil Gunn

The problem is Anna's driver patches for the tlv320aic sound codec
didn't ALL make it into the Linux mainline kernel when Raspbian first
released Buster. There have been 3 or more kernel updates in Raspbian
since June. The current kernel used by Raspbian, 4.19.66-v7+ has all of
Anna's patches & works fine.

Since the kernel you are currently using may have changed since you
modified your /boot/config.txt file try commenting out the dtoverlay=
line and running 'aplay -l'

Did the design of Draws boards change with respect to the eprom?
The overlay file required by the NW Digital Radio hats (UDRC, UDRC II &
DRAWS) grew too large to fit into the eeprom and is now loaded from the
boot file system. Also the Linux overlay code changed the names of some
of the overlay variables making any of the previous hat overlays that
are loaded from eeprom not work. Those hats require that the dtoverlay=
be used.

I would like to find out which NW Digital Radio hat you have:
and what version of the kernel you are running:
uname -r
and if you comment out the dtoverlay= line whether you still see the
problem of the hat not being enumerated.
aplay -l


Jonathan Magee <jmagee@...> writes:

That is not what I have found in practice. I created a clean sd card from
the official image for buster and to get the Draws Hat to be recognised I
had to add in the dtoverlay= line
When I did investigate it was trying to load in a device tree from the HAT
and failed. Did the design of Draws boards change with respect to the


On Fri, 27 Sep 2019 at 16:19, Basil Gunn <@basil860> wrote:

Basil's advice IS totally correct. If you have a DRAWS hat, NOT a UDRC
or UDRC II then you do NOT need to include the overlay flush line
dtoverlay=. It doesn't hurt anything to include the line but since the
overlay does NOT exist in eeprom for the DRAWS hat as it does for the
UDR & some of the UDRC II hats it really doesn't actually do anything.

If you have a DRAWS hat and find that you need to use dtoverlay= to get
the DRAWS driver to load and recognize the hat then you have other
problems, like the kernel you are using doesn't have all of Anna'a
patches or your upgrade path has left a bunch of stale overlays in
/boot/overlays directory.

On a new install using Raspbian with kernel version 4.19.66 or newer you
will not have that problem.

Jonathan Magee <jmagee@...> writes:

Hi Bernard
Basil's advice isn't totally correct, for some Draw Hats you need to
include in /boot/config.txt the line:
as well as the other lines. So the extra lines are (as per UDRC & UDRC II
hats )


That is what I had to do with my Draws Hat
Jonathan GI7KMC

On Thu, 26 Sep 2019 at 12:09, Bernard Pidoux <bernard.f6bvp@...>

Hi Basil,
Unfortunately /boot/config.txt modifications does not work.
aplay -l does not display card1: udrc
Here is the screen dump :

I suspect a conflict with forced sound through HDMI1 display.



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