Bypassing Vbus in TM4C129X (Getting USB interrupt without VBUS connection)

Sharadanand Karanjkar

Other Parts Discussed in Thread: EK-TM4C1294XL

Hi All,

In one of our projects we are using USB but because of some technical reasons we need to disconnect VBUS. But when I don't connect VBUS, I don't get USB interrupt. Is there any work around to bypass the VBUS connection?

regards,

Sharadanand

PS: TM4C129X is a USB device.

over 10 years ago

0 Amit Ashara over 10 years ago

TI__Guru**** 244400 points

Hello Sharad,

Is this is a custom board or using the EK-TM4C1294XL Connected LaunchPad?

Regards
Amit

0 Sharadanand Karanjkar over 10 years ago in reply to Amit Ashara

Intellectual 485 points

Hello Amit,

This is DK-TM4C129X board.

Regards,

Sharadanand

0 Amit Ashara over 10 years ago in reply to Sharadanand Karanjkar

TI__Guru**** 244400 points

Hello Sharadanand,

The Host can issue a DISCONNECT on the USB bus. The device has an interrupt bit for detecting disconnect which can be used for such an event w/o VBUS being switched OFF. Alternatively the Host can issue a USB Bus Reset. Is the host performing any of these actions and the interrupt bit being set in device?

Regards
Amit

0 Sharadanand Karanjkar over 10 years ago in reply to Amit Ashara

Intellectual 485 points

Hello Amit,

What I am observing is no interrupt is received when VBUS is not connected. I have no means to check if the host is generating such events or not. However, when I disconnect VBUS only (all other USB connections are present) while host is connected I receive disconnect event.

Regards,
Sharadanand

0 Amit Ashara over 10 years ago in reply to Sharadanand Karanjkar

TI__Guru**** 244400 points

Hello Sharadanand

You have to initialize the device as eUSBModeForceDevice in USBStackModeSet(0, eUSBModeForceDevice, 0);

when not using VBUS. The example code base for the ek-tm4c1294xl has usb_dev examples where the same is done.

Regards
Amit

Arm-based microcontrollers

Arm-based microcontrollers forum

Bypassing Vbus in TM4C129X (Getting USB interrupt without VBUS connection)