topic Re: USB detection issue for LPC1857 in LPC Microcontrollers

USB detection issue for LPC1857

lpcware — Wed, 15 Jun 2016 16:46:01 GMT

Content originally posted in LPCWare by shweta.kosamkar on Mon Jun 15 23:05:13 MST 2015
Hi All,

I am using LPC1857 USB in Host mass storage class. The issue I am facing is, if I power cycle the board within 1 sec (Switched off the system and switch it on within 1 sec), my system is not able to detect USB device. It resets the port permanently.
                I tried one thing i.e. make the USB power on (by turning on the regulator used for supplying power to USB) and wait for some delay about 500msec and then start initialize the USB. It works for some board, but not for all.

                Can you please help me on it?

                Thank you in advance.

Regards,
Shweta

Re: USB detection issue for LPC1857

lpcware — Wed, 15 Jun 2016 16:46:02 GMT

Content originally posted in LPCWare by shweta.kosamkar on Mon Jun 15 23:05:34 MST 2015

Quote: shweta.kosamkar
Hi All,

I am using LPC1857 USB in Host mass storage class. The issue I am facing is, if I power cycle the board within 1 sec (Switched off the system and switch it on within 1 sec), my system is not able to detect USB device. It resets the port permanently.
                I tried one thing i.e. make the USB power on (by turning on the regulator used for supplying power to USB) and wait for some delay about 500msec and then start initialize the USB. It works for some board, but not for all.

                Can you please help me on it?

                Thank you in advance.

Regards,
Shweta

Re: USB detection issue for LPC1857

lpcware — Wed, 15 Jun 2016 16:46:03 GMT

Content originally posted in LPCWare by MikeSimmonds on Tue Jun 16 05:40:04 MST 2015
Read the OHCI specs. There are certain delays required by the USB specifications. Perhaps your power on/power off is not respecting these.
Check your USB tracking etc. There are specific requirements for pull up resistors; and maybe you have bypass capacitors that are too strong.
Perhaps you didn't connect VBUS.

Perhaps a delay before enabling/configuring your USB host code and/or enumaerating the device .

Mike

Re: USB detection issue for LPC1857

lpcware — Wed, 15 Jun 2016 16:46:03 GMT

Content originally posted in LPCWare by mc on Tue Jun 16 10:16:19 MST 2015

Quote:
I am using LPC1857 USB in Host mass storage class. The issue I am facing is, if I power cycle the board within 1 sec (Switched off the system and switch it on within 1 sec), my system is not able to detect USB device.

Does MCU reset and run code correctly?
Do you mean when you power cycle after 1 second it works?