SN75DP130: System trouble shoot request

Hey Shinya,

I just want to make sure I understand the issue.  The issue is a sporadic functional issue when the device is repeatedly rebooted. In this broken state there is no display and it seems that aux communication is broken. Is that correct?

If possible can you have a look at the the VCC, VDD, and RSTN timings and make sure that they fit within the device spec every time you reboot the device?

The issue may be that when rebooting multiple times the power-up/ power-down timings may be violated putting the device into an unknown state.

I noticed that HPD is held high when you power cycle, would you be able to hold HPD low and see if this issue goes away?

Thanks for the reply. Let me add a comment below.

Since the power of the DP130 has not been operated, there is nothing to be confirmed about the power timing. If the low level is applied (approximately 150 ms) to the HPD during reboot while the power is still on, the event will not occur.

Thanks.

Hey Shinya,

Please have a look at the following E2E thread. In that issue they were having issues with AUX communication when repeatedly power cycling the device. The internal HPD controller seemed to be initializing incorrectly. This seems to be the case in your issue as well.

(14) SN75DP130: aux bus disconnected on some powercycles (DP source mode default register settings) - Interface forum - Interface - TI E2E support forums

Thanks a lot for your feedback and the information.

I have checked this forum. However, in my system configuration, AUX data communication is performed when the PC system is restarted without turning the device off and on, so it does not fit. If you repeat AUX communication to obtain display information during restart, communication will not work properly in rare cases. At this time, the AUX output signal waveform of the SN75DP130 will not be differential.

Since there is no abnormality when the power is turned off and on, I tried to apply a low-pulse signal to the HPD terminal of the SN75DP130 at the time of restart, and no abnormality occurred. We would like to examine whether HPD signal operation is required without stopping the power off/on.

If you find any hint or potential idea, feel free to let me know.

Thanks.

Hey Shinya,

What is your restart/ reboot procedure? Are you toggling EN? 

Shinya Sawamoto said:

If the low level is applied (approximately 150 ms) to the HPD during reboot

Shinya Sawamoto said:

ince there is no abnormality when the power is turned off and on, I tried to apply a low-pulse signal to the HPD terminal of the SN75DP130 at the time of restart,

Hi Vishesh,

Let me answer your question.

This problem occurs when we restart Windows using the Start > Power > Restart procedure. At this time, the EN connector does not toggle.

This is not a problem if we use the Start > Power > Shut down procedure to turn off the system, turn it on, and start Windows.

Thanks.

Hey Shinya,

Can you send the waveforms of the power of the device? If the entire system is doing a restart I don't understand why the DP130 power is being held constant. Additionally, have you tried swapping this part out to see if the issue goes away?

Hi Vishesh,

The problem is caused by repeating Windows Restart procedure. At this time, the power state remains S0 and the power is not disconnected. Although multiple devices are assembled using the same design, the occurrence of an event depends on the device. The frequency of occurrence also varies.

Thanks.