SK-AM64B: Quality Alert / Technical Support Request: Multiple UART Failures on SK-AM64B Evaluation Module

Hi Shikha,

This is not a known issue, and I am not aware of other reports of similar issues.  Here's a few questions to help debug-- 

1. Is the LD16 LED (Power good LED) is glowing after power on the board?
2. Were you able to see the USB Serial port under Ports (COM &LPT) on the Device manager?
3. If you are able to see the port on device manager and configured serial console Terra term, have you tried booting TI Linux SDK and seeing any LED toggling on board and not seeing any prints on console?  This make sure that the board is working and only UART Bridge is not working.
4. What is the serial number of the boards?  Can you please also share pictures of the boards?

Regards,

Melissa

Hi Melissa,

Thank you for your response.

Please find below the details requested:

1. LD16 LED Status: Yes, the LD16 (Power Good LED) is glowing after powering on the board.
2. USB Serial Port Detection: No, the USB Serial port is not listed under Ports (COM & LPT) in the Device Manager.
3. Boot Test with TI Linux SDK: We have not attempted this test, as the USB serial port is not being detected on the system.
4. Serial Numbers of Affected Boards:
   • SL# 37221000249
   • SL# 37221000143
   • SL# 27231000934

Please let us know the next steps for further debugging or resolution.

Regards,

Shikha

Contact: shikha@cdac.in

Hi Shikha,

1. LD16 LED Status: Yes, the LD16 (Power Good LED) is glowing after powering on the board.  Power is good on the board.
2. USB Serial Port Detection: No, the USB Serial port is not listed under Ports (COM & LPT) in the Device Manager.  My primary suspect is driver issue. I would recommend them to follow these instructions:- https://dev.ti.com/tirex/explore/node?node=A__ASbsvXLcIie6AhqNHYKxUw__PROCESSORS-DEVTOOLS__FUz-xrs__LATEST   Refer Connecting with Windows section :- If your Windows PC doesn't recognize the device, download and install the driver from here.
3. Boot Test with TI Linux SDK: We have not attempted this test, as the USB serial port is not being detected on the system.  Can you try booting with default SDK which is available on TI.com and see whether you see any heart beat LED toggling.

Regards,

Melissa

Hi Melissa,

Thank you for your continued support.

We would like to provide an update along with additional observations:

• The power supply being used for the EVM has been verified and fully complies with the recommended specifications mentioned in the guidelines.
• We have carefully followed all the troubleshooting steps shared by your team; however, the issue still persists.
• Currently, LEDs LD16, LD2, and LD13 are glowing, indicating that the board is powered and partially operational. However, LD18 (UART LED) is not glowing, which appears to be the main concern.
• When the board is connected to the PC via USB, no serial port is detected in the Device Manager.
• Find the relevant screenshots for your reference.

Based on these observations, it appears that the micro-USB (UART bridge) interface is not functioning. Since this issue has occurred across multiple boards without any changes in setup or configuration, it seems unlikely to be related to drivers or the host system.

We kindly request your guidance on the next steps for further diagnosis. If this indicates a potential hardware issue, please advise on the process for repair or replacement (RMA).

We appreciate your assistance and look forward to your response.

Regards,

Shikha

Contact: shikha@cdac.in

Hi Shikha,

Thanks for the additional observations.  Yes, the fact that LD18 is not glowing indicates that no power is available for CP2105 (UART Bridge).  Can you measure the voltage on TP76?

Regards,

Melissa

Hi Melissa,

Thank you for your guidance.

As requested, we have measured the voltage at TP76 for the affected boards. Please find the observations below:

1. SL# 37221000249 – 4.90V (While connecting the USB cable, LD18 initially glows briefly and then turns off.)
2. SL# 37221000143 – 5.19V
3. SL# 27231000934 – 5.19V

Based on these measurements, the supply at TP76 appears to be within range. However, LD18 is not staying ON (or not glowing at all in other cases), indicating that the CP2105 (UART Bridge) is still not functioning as expected.

Kindly advise on the next steps for further debugging or let us know if this points to a possible hardware issue requiring replacement.

Regards,

Shikha

Contact: shikha@cdac.in

Hi Shikha,

Did you try with another known good USB cable?

Also, can you please try on another host machine, possibly Windows machine?

You may want to monitor this thread for progress: (+) SK-AM64B: AM64x SK (PROC100A) - Debug console UART COM port no longer detected - Processors forum - Processors - TI E2E support forums

Thanks,

Stan

Hi Stan,

Thank you for your response.

Yes, we have already tested the boards using another known-good USB cable as well as on a different host machine, including a Windows system.

On the Windows machine also, the UART port is not detected in Device Manager. This confirms that the issue is not related to the USB cable or the host system. 

We will monitor the forum thread you shared for any relevant updates.

Please let us know if there are any further checks we should perform, or if this confirms a hardware issue requiring replacement.

Regards,

Shikha

Contact: shikha@cdac.in

Hello Shikha,
Thank you for the feedback. Do not hesitate to reach out to us if you have additional questions.

Please expect that certain delay in Melissa's response (earliest today COB) may be possible. 

Best Regards,

Borislav Lazarkov

Hi Borislav,

Thank you for the update.

We understand and will wait for Melissa’s response. Please let us know if any additional information or tests are required from our side in the meantime.

Looking forward to further guidance on this issue.

Best regards,
Shikha
Contact: shikha@cdac.in

Hello Shikha,

Please expect that certain delay in Melissa's response may be possible.

Thank you for your patience!

Best Regards,

Borislav Lazarkov 

Hi Shikha,

Could you please measure the below points on TP77 and share your feedback?

1. Measure voltage on TP77 (Please share the exact value).

2. Measure Resistance on TP77 with board powered off

Also can you please confirm you have the soldering/de-soldering station setup that can be used in a controlled ESD environment to perform the rework?

Regards

Deepak

Hi Deepak,

As requested, we have measured the voltage  and resistance at TP77 for the affected boards. Please find the observations below:

Yes, a soldering/de-soldering station is available for carrying out the rework in a controlled ESD-compliant environment. 

Looking forward to further guidance on this issue.

Best regards,

Shikha
Contact: shikha@cdac.in

Hi Shikha,

I understood that Resistance Measured unit is Mega Ohm, Could you please try giving a soldering touch up on Pin no 6, 7, 8 on U55 IC in one board and check?

Regards

Deepak

Hi Shikha,

Is the soldering touch up worked?, If not could you able to try replace the part U55 IC (CP2105)

Regards

Deepak

Hi Deepak,

Thank you for the suggestion.

We tried the soldering touch-up, but it did not resolve the issue.

We will proceed with replacing the U55 (CP2105) IC and update you with the result.

Best regards,

Shikha
Contact: shikha@cdac.in

Hello Shikha,

Please expect that certain delay in Deepak's response may be possible.

Thank you for your patience !

Best Regards,

Anastas Yordanov