AM5718: HDMI Hardware issue

Hi Biser.

Do you have a display connected on the HDMI?
Ans:Yes

Have you checked the signal levels on the HDMICONN_I2C signals?
Ans: There was no any signal on both pins [we measured at R795 and R796]

Thanks

Hi Biser,

gentle reminder.

Thanks & Best Regards,

Nikunj Patel

Hi Biser;

We have checked the "HDMI_DDC_SCL" pin at R795 resistor. When we plug the HDMI Cable to the board this signal goes to low. as per attched images.

1)  When HDMI Cable Plugged

2)  When HDMI Cable UnPlugged

Thanks & Best Regards;

Nikunj Patel

Nikunj,

The SCL pin should not go low and stay low.  This is invalid for I2C to function.  There must be a design or assembly issue causing this condition.  How many boards have you assembled?  Do they all behave the same?  Do you have a different HDMI display that you can plug in to see if the behavior is different?  Another test would be to use an AM571x IDK with the HDMI panel and to probe the signals to see what is different.

Tom

Hi Tom;

Thanks for your quick reply.

There must be a design or assembly issue causing this condition.  How many boards have you assembled?  Do they all behave the same?  Do you have a different HDMI display that you can plug in to see if the behavior is different?

Ans: We have checked with the 3 different boards and 3 different HDMI Display and all have the same issue.

Another test would be to use an AM571x IDK with the HDMI panel and to probe the signals to see what is different.

Ans: We does not have the AM571x IDK board so we can't measure this SCL pin. can you help us to probe the signals if you have AM571x IDK Board?

Thanks & Best Regards;

Nikunj Patel

Nikunj,

Sorry, I clicked the wrong button.  I did not mean to indicate that the question is answered.

Tom

Nikunj,

We know that the IDK works.  SCL being held low is an invalid I2C bus condition.  It blocks all communication.  The point of having you probe the IDK was not to see if the SCL was held low.  It was for you to measure the various signals around the TPD12S016 to determine what is different in the various operating states.  I recommend that you acquire one for this purpose.

Your HDMI schematic implementation is slightly different from the one on the IDK.  Have you cross-checked the differences to make sure that they meet your requirements and software driver?  Can you modify the connections on one of your boards to make it match the IDK implementation to see if that enabled success?

Tom

Nikunj,

I see that you had a previous E2E open on this topic at: 

.  What was the resolution on the I2C in that thread?  You mentioned that you had functional communication in standard I2C pinmux mode.  I see that you asked about the pin definitions being reversed between standard I2C and HDMI I2C.  This reversal is known and it is true.  Do you have this connected incorrectly on your board for HDMI I2C use?

Tom

Hi Tom;

Your HDMI schematic implementation is slightly different from the one on the IDK.  Have you cross-checked the differences to make sure that they meet your requirements and software driver?  Can you modify the connections on one of your boards to make it match the IDK implementation to see if that enabled success?

Answer: yes there was only one Change of gpio control differ from IDK. but we already change software configuration for that and we measured voltage and it was proper 3.29 volt. Also as per your suggestions I will check with removing gpio connection and change the R559 to 0 ohms.

What was the resolution on the I2C in that thread?  You mentioned that you had functional communication in standard I2C pinmux mode.  I see that you asked about the pin definitions being reversed between standard I2C and HDMI I2C.  This reversal is known and it is true.  Do you have this connected incorrectly on your board for HDMI I2C use?

Ans: we have correct connection on our board.

You can check the image of HDMI connection's schematic which was post by me on staring of this thread.

Thanks & Best regards;

Nikunj Patel

Nikunj,

In the other post, you show scope images of I2C data transfers.  What is different from then?  Now you are reporting that the SCL net is held low as soon as the HDMI is plugged in.

Do you know which side is holding it low?  Can you provide the picture shown above for both the connector side and the processor side?

Tom

Hi Tom,

We have configured HDMI_DDC_SCL as normal I2C_SDA and HDMI_DDC_SDA as normal I2C_SCL mode using spl-uboot pin MUX configuration only for damage or proper soldering of pin checking as per describe in other post.

Thanks & Best regards;

Nikunj Patel

Nikunj,

But how does that work with the pins swapped?

Tom

Nikunj,

Were you able to communicate with an HDMI display while in the Linux I2C mode?  Or were these captures made while there was no display attached?

Tom

Nikunj,

OK, let's go back to this question:

In the reported failure case - do you know which side is holding it low?  You may have to cut traces or lift IC pins to determine this.

Can you provide the picture shown above (where the signal is pulled static low) for both the connector side and the processor side?  Please make sure that the 0V level and the vertical deflection (V/div) is clearly shown in the scope capture.

Tom

Hi Tom,

I have captured images as listed below .

Now we have configured our board as similar to the IDK[De-Populate R561 and R1068,Changed R559 from 10K to 0 ohm].But still on SCL after connecting to HDMI connector we are not getting proper voltage output as well as it isn't looks a like clock.

1. While HDMI not connected and measured at R795. 

2) HDMI not connected and measured at R796.

3) HDMI not connected and measured at R560.

4) HDMI not connected and measured at R562.

5) HDMI connected and measured at R796.

6) HDMI connected and measured at R795.

7) HDMI connected and measured at R560.

8) HDMI connected and measured at R562.

Is there still something that i need to update from harware pointof view please guid us.

Thanks and Best Regards,

Nikunj Patel.

Nikunj,

Two comments here:

1)  We know that the IDK works.  Therefore, if you make the connections and resistors match the IDK, your board will work.  This indicates that there is something in the design or the assembly that is not like the IDK.  You should get an IDK EVM to enable comparison during debugging.

2.  You crossed my requests.  I was asking for scope captures to be taken from both sides of the TPD12S016 whith the board and test conditions same as shown in the post on Oct 18.

Tom

Hi Tom;

Sorry for late reply.

We have done test as per below.

We removed the "R795" resistor to check the issue of level shiftor ic. but after removing the "R795" Resistor still, the signal goes low of level shifter IC pin.

Thanks & Best Regards;

Nikunj Patel 

Nikunj,

As I stated in my 10/23 post.  I need to see the scope captures requested.

Tom

Hi Tom,

We does not captured the the scopes picture right now but we measured the voltage at both side as below. we have do some changes for another testing so i will captured the scope images after two days and then send to you.

1. HDMI DISPLAY CABLE UNPLUGGED
   1. HDMI Connector Side
      1. HDMICONN_I2CSCL(J24-pin17) : 4.9Volt
      2. HDMICONN_I2CSDA(J24-pin18) : 4.9Volt
   2. Processor Side
      1. AM572X_HDMI_DDC_SCL(R795) : 3.29Volt
      2. AM572X_HDMI_DDC_SDA(R796) : 3.29Volt
2. HDMI DISPLAY CABLE PLUGGED
   1. HDMI Connector Side
      1. HDMICONN_I2CSCL(J24-pin17) : 100-200 millivolt
      2. HDMICONN_I2CSDA(J24-pin18) : 4.83 Volt
   2. Processor Side
      1. AM572X_HDMI_DDC_SCL(R795) : 0.483 Volt
      2. AM572X_HDMI_DDC_SDA(R796) : 3.23 Volt

Thanks & Best Regards;

Nikunj Patel

Nikunj,

I asked for the scope pictures as I want to see the low levels during data transfer.  The measurement provided are not sufficient.

It is interesting to note that your static measurements show SCL static low.  This is a hung condition.  The SCL should always return high after a transfer is completed.

Tom