I'm currently trying to get USB communication with my custom board with the LPC55S69 64-pin package, but I'm able to get it working on the LPC55S69-EVK board through P9.
The image I've attached shows the connections we have coming in from the USB cable, and we've verified that the 5 wires coming out of the USB-C cable are as follows:
Red -> VBUS
Grey -> GND
Green -> D-
White -> D+
Blue -> CC1
I've probed D+ and D- on our custom board, and both lines remain low always. I've also tried with USB1_3V3 tied to 3.3v core voltage, as well as left floating, and neither way seems to work.
Interestingly, wen I set my pin package to the 64 pin version and ran my code on the EVK, even though the USB pins shouldn't match the board, it's still able to communicate and be interrupted despite D+/- being set to pins 24 and 25 instead of pins 35 and 36.
Ultimately, my best guess is our device isn't being detected as a USB device and the D+ and D- lines aren't getting driven high and low as a result. I can't seem to figure out why this would be though, so any help would be appreciated.
Hi lindsey-anderson
LPC55 ESD is only 2kV . we need ESD protection on it
https://www.nxp.com.cn/docs/en/application-note/AN13449.pdf
To improve EMC performance:
- Recommend using TVS arrays for ESD protection on VBUS, D+, D-, and ID.
- Connect the common mode choke to USB signal.
- To isolate high frequency noise, use Ferrite beads on power pin (VBUS, GND).
For more details about hardware design guideline, see Hardware Design Guidelines for LPC55(S)xx Microcontrollers (document AN13033).
LPCXpresso55S69 HS USB schematic, FYI:
Thanks,
Jun Zhang
Thank you for the reply.
We currently have a TVS array as shown in the snapshot I sent with the part number D5V0F4U5P5-7.
We also don't have a common mode choke attached to the data lines currently, but since we're not currently seeing any pull-up or data on D+ or D-, I don't know that this would help our current situation.
We also don't currently have a ferrite bead attached, but we noticed the note in the LPC55S69 schematic stating there's a 0-ohm resistor in place of the ferrite bead shown, so it seems like it should work without it.
We captured the VBUS line when first plugging in the USB connector to verify that the rise time and noise observed were within spec to initialize the USB. I've attached an image of that data, but the white signal shows the resulting waveform with our surge current limiting MOSFET, and the yellow signal shows the VBUS line with this MOSFET bypassed. The two rise times observed were 626uS with the slow start in place, and 370uS without it.
Many of these notes might make improvements to noise, but I'm not sure how to get it to communicate in the first place. I've verified we're getting a steady 5.1V to the VBUS pin on our microcontroller, and I've verified the rise time looks to be within reason, but I still can't figure out why D+ isn't being pulled high, and why the USB_DeviceCallback isn't getting called on our custom board, but is on the LPC55S69, and the MCU Link we custom programmed.
I'm including a screenshot of the MCU side of our board design to verify our connections on that side seem correct, but one thing that has changed is that we've connected the USB0_3V3 and USB1_3V3 lines up to the +3V3 rail which isn't captured in the schematic.
Let me know if you can think of any other reason USB couldn't communicate or enumerate.
Thanks,
Lindsey
