AM623: USB DFU device not detected on custom board with SoC AM623

Yakov Kasyanov

Part Number: AM623
Other Parts Discussed in Thread: SK-AM62

Hello TI experts,

I am working on a custom board based on the AM623 SoC, currently in the bring-up stage.
One of the interfaces I am using is USB0 in device mode. To validate the hardware, I configured the board to boot in USB DFU mode and connected it to a PC.
For device detection, I am using Thesycon USB Descriptor Dumper, which successfully detects the SK-AM62 EVM in USB DFU mode. However, my custom board is not detected by the host PC (no USB enumeration observed).

What I have checked so far:

Boot mode is configured for USB DFU
Board powers up correctly (all rails look valid)
USB is connected to a host PC via USB connector
Same setup works with SK-AM62 EVM

I suspect the issue may be related to the USB hardware design. The USB device implementation schematic is shown in the screenshots attached to this message.
Could you please advise what might be the problem?

Any guidance on debugging this issue would be greatly appreciated.

Thanks in advance,
Best regards
usb sch.png usb sch 2.png

2 months ago

+1 Stanislav Stilyanov 2 months ago

TI__Mastermind 25080 points

Hi Yakov,

I would recommend these steps to see if USB boot begins to start up:

- Remove BAT54 protectors. I'm not sure they are USB friendly

- Remove C47. Ensure VBUS is connected to R11 only and VBUS is not propagated elsewhere (disconnect from other nets) . I can see your device can be self-powered, is it correct?

- R197 - Value doesn't correspond to datasheet

Other comments:

- I can see CC1 and CC2 are pulled down which means your USB port is USB peripheral/device, is this correct? In this case USB0_DRVVBUS is not functional and cannot be used. It can be left unconnected. DRVBUS works only in host mode of USB controller.

- The below part looks like is switching between self-powered mode and VBUS- powered mode, is this correct? If yes, there may be needed a connection dot between two nets?

- Please revise the series resistor values on transistor gates. Usually they need to be ohms, instead of kilo ohms

Best regards,

Stan

0 Borislav Lazarkov 2 months ago in reply to Stanislav Stilyanov

TI__Intellectual 1690 points

Hello Yakov,

For the BUS_SENSE netline, please review in the AM62x Datasheet in section 8 Application, Implementation, and Layout, point 8.2 Peripheral-and Interface-Specific Design Information, point 8.2.3 USB VBUS Design Guidelines.

For the USB0_RCALIB pin an external 499 Ω ±1% resistor must be connected between this pin and VSS and the maximum power dissipation for the resistor is 7.2mW.

Best Regards,

Borislav Lazarkov

0 Yakov Kasyanov 2 months ago in reply to Borislav Lazarkov

Prodigy 30 points

Thank you for the quick response. I will now try to implement your recommendations.

0 Borislav Lazarkov 2 months ago in reply to Yakov Kasyanov

TI__Intellectual 1690 points

Hello Yakov,

Hope that this helps.

Feel free to reach to us if there are any other open points.

Best Regards,

Borislav Lazarkov

0 Yakov Kasyanov 2 months ago in reply to Stanislav Stilyanov

Prodigy 30 points

The device can be powered from an external 9V power supply.
Correct. The USB port should operate in device mode.
Thank you for your advice. I will now proceed with implementing it.

0 Borislav Lazarkov 2 months ago in reply to Yakov Kasyanov

TI__Intellectual 1690 points

Hello Yakov,

If this solved your problem, I am closing the thread.

Best Regards,

Borislav Lazarkov

0 Yakov Kasyanov 2 months ago in reply to Borislav Lazarkov

Prodigy 30 points

I've implemented some of your advice, but not all of it yet, and the USB is still not working. So if possible, I would ask you to keep this thread open for a little longer.

0 Borislav Lazarkov 2 months ago in reply to Yakov Kasyanov

TI__Intellectual 1690 points

Hello Yakov,

Ok, I will keep it open.

Best Regards,

Borislav Lazarkov

0 Luis Parga 2 months ago in reply to Borislav Lazarkov

TI__Intellectual 1320 points

Hi Yakov,

I also see that your schematic is missing the recommended 6.8V Zener diode on the USB_VBUS pin. Please advise if this is intentional.

Best regards,

Luis Parga

0 Yakov Kasyanov 2 months ago in reply to Borislav Lazarkov

Prodigy 30 points

It looks like the problem is indeed with the calibration resistor. I ordered a resistor with the required value, but it will be delivered in 5 days. So I'll only be able to confirm that your recommendations worked after that time.