TUSB546EVM: Display Port not working

Hi Juliet,

Thanks for reaching out. Have you tried changing the EQ settings on the 546 EVM board? For DisplayPort, this would be the DPEQ1 and DPEQ0 pins:

If the EQ is not high enough (or too high), it can cause the signal to not pass through. Having two EVM boards in the signal path may be adding extra loss, so try increasing the EQ level.

Do you have a USB-C monitor? It would be good to see if the 546 EVM alone will pass data from your host to an attached monitor if you have one.

Best,

Shane

Hello,

I have tried all of those positions. Is there something else that could be impacting the DP?

Hi Juliet,

Are you powering both of the boards with a 5V supply through the barrel jacks? In DP only mode, you should use an external supply so the board has enough power.

546 EVM user's guide:

564 EVM User's guide:

Another thing to check is that the I2C_EN (JMP7) pin is pulled low. This puts the 546 into GPIO mode, which is standard for this EVM.

Best,

Shane

I verified that JMP 7 is pulled low. There was no barrel jack charging cable that came with the kit, is there a specific one to use? When I look at the schematic, it looks like the barrel jack and the USB-B power jack go to the same power supply: 

Juliet DeNapoli said:

is there a specific one to use?

You need to use a 5V output barrel jack. Make sure it is able to provide at least 1A of current as well.

Juliet DeNapoli said:

it looks like the barrel jack and the USB-B power jack go to the same power supply: 

You're correct that they do go to the same supply. What I believe is happening is that the USB-B VBUS is not supplying enough power for both of the EVMs.

The USB port will typically be limited to 900mA, which will be shared between the 546 and 564 EVMs when they are used together (They both draw power from the upstream USB port). Adding a 5V external power source should give the EVMs enough power to pass your DP signal through.

Can you try adding a 5V barrel jack to the 546 and 564 boards?

Best,

Shane

To clarify, when you use the 5V barrel jack don't plug in the USB cable. The external supply should give enough power on its own without a USB connection.

If it still doesn't work after trying this, I'll try to recreate the setup myself.

Best,

Shane

Juliet DeNapoli said:

Is there a specific barrel jack power cable that you would recommend?

Any 5V barrel jack will work, as long as it can provide at least 1A of current. Do you know what voltage the barrel jack supply was that you plugged in?

The part you've linked provides 5V, but the current will be limited by the USB port you plug it into. We typically use wall-adapter barrel jacks here. I found one on amazon that fits the specs correctly, so anything like this should work:

https://www.amazon.com/YETAIDA-100-240V-Adaptor-Universal-Adapter/dp/B07R9ZVCHF/ref=asc_df_B07R9ZVCHF/?tag=hyprod-20&linkCode=df0&hvadid=343242953198&hvpos=&hvnetw=g&hvrand=4214865137970159739&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9026941&hvtargid=pla-775037475002&psc=1&mcid=d0cd647a67bf379db7a63e72b00a74ee&tag=&ref=&adgrpid=71764766831&hvpone=&hvptwo=&hvadid=343242953198&hvpos=&hvnetw=g&hvrand=4214865137970159739&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9026941&hvtargid=pla-775037475002&gclid=EAIaIQobChMIu8CAy9bdhQMVeTbUAR37dgQZEAQYBSABEgK5QfD_BwE 

In the meantime, I'll work on re-creating your setup to make sure there aren't other issues with the boards.

Best,

Shane

I was able to find a barrel jack power supply over here, just one though. I tried plugging it into the 564 board and kept the 546 board powered by the USB-B, I figured this would give enough current to the 564 board. However, I still saw no display. Is there a reason that both boards will need the barrel jack charger? If both are being powered independently, I am confused why there would be an issue with there being not enough current. 

Thanks for the recommendation though! I will order one now.

Juliet DeNapoli said:

Is there a reason that both boards will need the barrel jack charger?

This is because when using 4 lane displayport, you don't use the USB connection. So the power will come from the barrel jack.

I've got the setup together in the lab, and was able to verify the 546 and 564 EVMs work to pass video individually. Let me work on configuring the boards to operate together. I'll aim to have an update tomorrow.

Best,

Shane

I connected the barrel jack supply to both boards, and the Display Port is still not showing. Were you able to get it working on your end? Maybe there is a specific configuration of all the jumpers I didn't do correctly? Or the switches?

Hi Juliet,

Thank you for your patience. I see the same issue you are describing, and have narrowed down the problem to the communication between the PD controllers on both boards.

In a USB/DP alt-mode system, the Power delivery (PD) controller on the DFP will communicate with the PD controller on the UFP to switch into USB alternate mode. Once both PD controllers agree to use alt-mode, they configure our 546 and 564 MUXes to the correct pin assignments.

The issue I saw in the lab today was that the PD controllers didn't seem to negotiate alt-mode correctly when using the 546EVM and the 564EVM together. Individually, both of these boards work without issue, but together they refuse to pass DisplayPort signals like HPD and AUX over the type-C connection. I believe there is some conflict happening between the TPS65982 on the TUSB546EVM and the 65982 on the TUSB564EVM.

When I use a protocol analyzer between the two boards, they are able to pass video correctly. This leads me to believe there is something wrong with the communication between these two PD controllers specifically.

Let me keep looking into this. I'll try the same test using the TUSB1146EVM instead of the 546 EVM, which uses a newer PD controller (TPS65987D). Hopefully this will confirm whether it is a problem with the TPS65982 specifically.

I apologize for the delay, I'll aim to have an update early next week with anything I've found.

Best,

Shane

Hi Juliet,

Today I was able to get the signal through both the 546 EVM and one of the 564 EVMs we have in the lab. Here's an image of the pin configuration I used on the 546 EVM:

The issue I ran into before was because I had plugged the barrel jack power into the 564 EVM before plugging in the type-C connector. Try using a barrel jack only on the 546 EVM first, then connect the boards via the type-C cable with no barrel jack on the 564. The wall adapter I used had a 5V/3A output, enough to supply both boards.

Here is an image of my setup. The cables I used may have different loss values then your cables, so our ideal EQ settings could be different:

Even with the correct board settings, I had to flip the cable orientation a few times before the DP signal went through. I recommend trying to power cycle the board and flip the orientation of the type-c cable to see if your signal will go through.

I'll mark this as resolved for now, but let me know if there's anything else I can help with and the thread will re-open.

Best,

Shane

Thanks for getting back to me with this. I have trying to get it to work again, but still having trouble. The 564 EVM board you are using looks different than the one here.

Is this a different version of the board? I can't seem to find the one you are using.

Hi Juliet,

I grabbed a 564 board we use in the lab for testing, but I realize that is likely not the same one that is available on TI.com.

Are you using this version of the board? (HSDC025A)

If not, could you send a picture of the EVM board you have? I'll see if I can find the same version to more accurately model your setup.

Best,

Shane

Yes, that is the board I am using. I was having trouble attaching a photo.

I looked around our lab and couldn't find that EVM board, so I sent out an order for one. I anticipate the board will arrive later this week, and I'll keep you updated when I've got it here.

In the meantime, I recommend testing the 546 board independently if you're able. I remember you mentioned the 564 EVM works by itself, so it would help to know if the 546 EVM is causing the issue. An easy way to test this would be to use a USB-C monitor.

Best,

Shane 

Hi Juliet,

I received the 564 board that you're using today and was able to pass DP signals through both boards together.

Here's an image of my setup:

I found that using this 564 EVM, there was no issue plugging a barrel jack first, then connecting the type-C plug. Seems like that may just be an issue on our test board...

Here are the pin configurations I used on the 564 EVM:

Here are the configurations I used on the 546 EVM

I had to flip the USB-C cable a few times before the DP data went through, but otherwise had no problems. Can you try configuring your boards like mine to see if the signal will pass?

Best,

Shane