2412462_en-US

minimal configuration to negotiate higher current limit on USB

I have a device that can be powered over USB with an MCXN947 processor on it. I don't currently have the USB configured, just pulling 5V. However, I would like to raise the current limit which seems to default to 100mA.

What's the minimal configuration I can do to raise the current limit? In MCUXpresso config tools, I tried setting up USBFS. It requires at least one interface, so I tried to set up DFU. I managed to get things to build mostly, but the config tools generate a file timer_queue.c that defines a SysTick_Handler that conflicts with the FreeRTOS port.c SysTick_Handler.

1) Is there something better I can do to try to raise the current limit?

2) If setting up this DFU interface is as good as anything else, how should I resolve conflicts between autogenerated code and the FreeRTOS port?

Re: minimal configuration to negotiate higher current limit on USB

Hello @robert_hines

Yes, a USB device must declare its required power in the bMaxPower field during USB enumeration.

To draw more than 100 mA, I recommend configuring your device as a USB HID or USB CDC device, as these are generally easier to implement than DFU.

Thank you.

Alice