LPC55s69 USB1 HS as CDC_VCOM and ISP peripheral

[Deeps_bang]

Hi Team,

The  LPC55s69 is used as main controller in our project.

can we use USB1HS itself for two purposes i.e to serve as CDC_VCOM and  as ISP peripheral during ISP bootloader mode? ....As both tasks appear independently .

Will  their be any detection issue??

Any premeasure or any particular settings to be done while doing so?? 

Thanks & Regards

Deep_Bang

[Deeps_bang · Accepted solution]

Hi Alice,

The USB detection issue solved by replacing divider circuit resistance 20k to 0k (DNI) at  'USB1_VBus'.

Thank you for the support.

BR,

Deep_Bang 

[Deeps_bang]

HI Alice,

Thank you for response

Why i raised this question is, for few fabricated boards USB detection working fine. But for few boards USB device enumeration as HID Device  not happening . i.e Facing USB detection issue for few boards. PFA schematic of USB part. what could be the reason for this??

BR

Deep_Bang

[Alice_Yang]

Hello @Deeps_bang 

Is there relationship with ISP? If do no enter ISP mode, these boards can work well?

BR

Alice

[Deeps_bang]

Hi Alice,

In ISP mode working fine. Detection problem in normal mode. 

According to our analysis, problem might be at voltage divider circuit for USB1_VBus. 

The LPC55s69 boards A0 /A1 version changes might be causing this detection issue .

for few boards detection will happen with divider ckt.

For detection error boards have plan to verify without this bias ckt.

Any input on this??  

BR

Deep-Bang

[Alice_Yang]

Hello @Deeps_bang 

1) "The LPC55s69 boards A0 /A1 version changes might be causing this detection issue ."

->> Do you mean the issue can reproduce on nxp demo board LPCxpresso55s69-evk A0/A1? If yes,  you can tell me steps, I help to check on my side.

2) There is an application note, you can download and have a look:

https://www.nxp.com.cn/docs/en/application-note/TN00071.zip  

BR

Alice

[Alice_Yang]

Hello @Deeps_bang 

Yes, you can.

 ISP peripheral  is in ISP mode used, it means in boot rom code, while "serve as CDC_VCOM" is in your application code, they are in different stages.

BR

Alice