[MinnowBoard] HDMI level shifters and revision A4

Leigh Gawne leighgawne at gmail.com
Fri Jun 12 11:09:46 UTC 2015


Hi Dave,

 

As I suspected, this is indeed a hardware problem and nothing to do with firmware. I built a small adapter board based around the PTN3360B level shifter that takes the AC coupled DDI output from the E38xx and creates DVI/HDMI compliant drive. And hey presto, everything works absolutely perfectly with the TFP401. See attached images.

 

BTW, I also have around 10 other minnows, 9 of which not work at all with my Samsung monitor… the one that does is really on the limit, and I can see it is the same problem of this missing level shifter as it works fine when I use my adapter. I have seen quite a few other threads about blank displays when booting the minnow, and I would expect that this is also the root cause. Hence, very much looking forward to the A4 revision.

 

Regards,

 

Leigh

 

From: elinux-MinnowBoard [mailto:elinux-minnowboard-bounces at lists.elinux.org] On Behalf Of Anders, David
Sent: 08 June 2015 07:04
To: MinnowBoard Development and Community Discussion
Subject: Re: [MinnowBoard] HDMI level shifters and revision A4

 

Leigh,

 

Indeed if you will check I opened the bug report….

 

There were some specific hacks I used in the coreboot as a test…

 

Dave Anders

 

 

From: elinux-MinnowBoard [mailto:elinux-minnowboard-bounces at lists.elinux.org] On Behalf Of Leigh Gawne
Sent: Monday, June 8, 2015 12:52 AM
To: 'MinnowBoard Development and Community Discussion'
Subject: Re: [MinnowBoard] HDMI level shifters and revision A4

 

Hi Dave,

 

According to the bug report, this issue shouldn’t be present with coreboot, but it most definitely is in my case. I have taken a short video to show my system running coreboot with a system test in progress. This board is one that is on the limits, and hence the display is intermittent - https://youtu.be/ivSl9617RlM 

 

If this is a firmware issue of sorts, I would be very happy to help test any fix on my platform. I am under some time pressure to get all of this working, and this is obviously a serious problem for me.

 

My implementation of the TFP401 and associated electronics works perfectly with other sources (PC, etc.) and everything is length matched, impedance controlled with decoupled supplies exactly as per TI’s design requirements, so I am fully confident this part is exactly as it should be.

 

I am going to try with an HDMI repeater to see if this solves my issue. I’ll keep the list updated with my findings.

 

Thanks,

 

Leigh

 

From: elinux-MinnowBoard [mailto:elinux-minnowboard-bounces at lists.elinux.org] On Behalf Of Anders, David
Sent: 08 June 2015 00:45
To: MinnowBoard Development and Community Discussion
Subject: Re: [MinnowBoard] HDMI level shifters and revision A4

 

Leigh,

 

I’ve tested the TFP-401 with the with the correct level shifters implemented on the MinnowBoard Max and it made no difference to functionality. We did use a HDMI/DVI analyzer on the board and verified the correct levels were implemented(on the modified board). The specific issue at hand appears to be related to how the video controller handles the DVI (not HDMI) legacy modes. I was able to replicate this issue using a NUC (which does have the correct level shifters). Once I upgraded the firmware on the NUC the issue went away…

 

No schedule for A4 has been announced yet…

 

Dave

 

 

 

From: elinux-MinnowBoard [mailto:elinux-minnowboard-bounces at lists.elinux.org] On Behalf Of Leigh Gawne
Sent: Sunday, June 7, 2015 1:01 PM
To: MinnowBoard Development and Community Discussion
Subject: Re: [MinnowBoard] HDMI level shifters and revision A4

 

Hi Dave,

Thanks for the info, however in my case I must say this does not look like the firmware issue mentioned below - I have tested this with UEFI and coreboot/seaBIOS and this makes no difference, unlike that stated in the ticket. 

Based on the fact that there is a known issue (https://bugzilla.yoctoproject.org/show_bug.cgi?id=7027) with the HDMI interface being out of spec and with the testing I have done everything points at a hardware problem. Some boards just about work, others don't at all. EDID is all working fine. Unless the HDMI drive strengths or levels can be adjusted by software, then I can't see how a firmware fix would improve anything here, any thoughts? 

Hence back to my earlier question about the A4 revision of the board with proper HDMI compliant signals - is this available yet? If so I can very easily check to see if this solves my problem. 

Thanks,

Leigh

On 7 Jun 2015 18:34, "Anders, David" <david.anders at intel.com <mailto:david.anders at intel.com> > wrote:

Leigh,

 

See this bug report:

 

https://bugzilla.yoctoproject.org/show_bug.cgi?id=7719

 

specifically the TFP401 and TFP501 chips from TI are not working with the MinnowBoard Max. the issue appears to be a firmware , not hardware issue, and is being worked on…

 

thanks

Dave

 

From: elinux-MinnowBoard [mailto:elinux-minnowboard-bounces at lists.elinux.org <mailto:elinux-minnowboard-bounces at lists.elinux.org> ] On Behalf Of Leigh Gawne
Sent: Sunday, June 7, 2015 2:43 AM
To: MinnowBoard Development and Community Discussion
Subject: Re: [MinnowBoard] HDMI level shifters and revision A4

 

Hi Dave,

I am using the TI TFP401 as the DVI decoder. 

I thought about spinning another revision of the board with an additional level shifter, but given that these are present on the A4 revision, my preference is just to get this revision and everything should play nice.

Thanks,

Leigh

On 6 Jun 2015 11:21 pm, "Anders, David" <david.anders at intel.com <mailto:david.anders at intel.com> > wrote:

Leigh,

 

We have found that there are some DVI receiver chips that are of issue with the minnowboard max. which chipset are you using to covert from HDMI/DVI to LVDS?

 

Dave

 

From: elinux-MinnowBoard [mailto:elinux-minnowboard-bounces at lists.elinux.org <mailto:elinux-minnowboard-bounces at lists.elinux.org> ] On Behalf Of Leigh Gawne
Sent: Saturday, June 6, 2015 6:46 AM
To: elinux-minnowboard at lists.elinux.org <mailto:elinux-minnowboard at lists.elinux.org> 
Subject: [MinnowBoard] HDMI level shifters and revision A4

 

Hi guys,

 

I have a customised daughterboard for the Minnoxboard Max which includes an HDMI to LVDS subsystem. During test, I have found that some boards are unable to drive the connected LCD display panel. Further investigation leads me to believe that it is the missing level shifters on the Minnowboard Max which mean that this is not working as expected (connecting other HDMI sources to the board, i.e. PC, etc. work absolutely fine. Inspection of the diff pair levels on a scope shows that it is definitely marginal). 

 

I understand that revision A4 of the board (https://bugzilla.yoctoproject.org/show_bug.cgi?id=7027) will include these level shifters. My question is whether this revision of the board is available yet, and if so, how I couple go about ordering a couple of them for test to ensure it solves my problem. I purchase around 10 boards around a month or so ago, and these are all revision A2.

 

Any insights or additional information would be most helpful.

 

Regards,

 

Leigh


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