Hot!Getting USB to work on Explorer 16/32 with PIC32MZ2048EFH100 PIM

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Kerry_Imming
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2017/04/26 15:18:14 (permalink)
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Getting USB to work on Explorer 16/32 with PIC32MZ2048EFH100 PIM

I have a question on how P1_VBUS is supposed to work on the Explorer 16/32 development board.  I'm not an expert on USB, but I have spent a good amount of timing studying the PIC32MZ datasheet and the USB specifications.
 
I have the USB-A connector working now, but I had to disconnect the USB-C VBUS (cut trace) and wire P1_VBUS at PIM pin 1 directly to J32-1.  Details:
1.  Cut trace from PIM pin 1 on top side of board.  It's the wire near the white triangle pin-1 indicator. 
2.  Wire a jumper on back side of board from J32 pin 1 to PIM pin 1.
! Note/warning that this also moves P1_VBUS_E over to this new VBUS. 
 
I believe that VBUS has to get to +5V, but I don't find enough details on how VBUS is used inside the PIC32MZ USB module to confirm.  I can confirm the bringing it to +5V got the USB bus working for me.
 
In looking at the Explorer 16/32 schematic (USB-C section) I see that P1_VBUS is connected through a diode to the +3.3V supply.  This clamps it at about 3.9V, so I don't see how it can ever get to +5V.  There are a lot of options with USB what with legacy plus USB-C plus device/host mode, so there certainly may be circuit details I've missed.
 
Can anyone shed light on how this should work?  Does anyone have the on-board USB working as-is?  I understand there is a PicTail USB adapter, but the USB-A port should have everything I need.
 
- Kerry
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    klockwood
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    Re: Getting USB to work on Explorer 16/32 with PIC32MZ2048EFH100 PIM 2018/03/06 15:08:50 (permalink)
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    Did you ever hear anything back or figure this out?  I just tried downloading the USB Device -CDC Basic demo for my Explorer 16/32 board with a PIC24FJ256GB410 PIM and programmed it but the PC I am connected to doesn't even see the Explorer 16 as a COM port.  I am wondering if I should try what you did?
    #2
    Kerry_Imming
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    Re: Getting USB to work on Explorer 16/32 with PIC32MZ2048EFH100 PIM 2018/03/08 09:29:02 (permalink)
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    klockwood
    Did you ever hear anything back or figure this out? 



    No to both.  The PCB "fix" I did solved the problem for me and I didn't look much deeper into trying to figure out how VBUS is used inside the chip.
     
    I don't see much downside to the board change I did as it can be reversed if necessary.
     
    - Kerry
     
    #3
    Jim Nickerson
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    Re: Getting USB to work on Explorer 16/32 with PIC32MZ2048EFH100 PIM 2018/03/08 09:39:33 (permalink)
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    I wonder if there is a Harmony USB project for this combination ?
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