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I designed a custom RP2040 to control some 24V LED strips. The official hardware design guide from the Raspberry Pi Foundation is what I followed for my design. It was then sent out to JLCPCB for the fab and I used their stencil to solder the SMD components on 2 of the 5 PCBs on a hotplate. Before I soldered the THT components, I plugged in the USB port (J1) to see if the RP2040 is detected by the PC which it didn't for both boards. The device manager doesn't show anything plugged in on the COM port. :(

The USB 5V goes to a 3.3V regulator (AP7365-33EG-13) to power the RP2040. I measured 3.3V & 1.1V on capacitors connected to the IOVDD & DVDD pins respectively. Thus the RP2040 is at least powered on properly. I tried placing the BOOTSEL button without soldering it, held it down while plugging in the USB and then releasing it; still no luck.

Can anyone possibly spot the issue I'm dealing with here? I'm attaching my schematic, board layout, and anything else that might be useful in figuring this out.

RP2040 Schematic Power Schematic PCB Top Layer PCB Bottom Layer PCB Invisible Planes

Below is what I can think might be causing the problem:

  • Bad USB data line. I used 22 ohm resistors instead of 27.
  • The Run pin on the RP2040 needs to be pulled up to 3.3V with a resistor (but I believe it's already pulled up internally)
  • Possible shorts or bad solders underneath the QFN package of the RP2040

Link to schematic and board layout.

Agriculex
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  • So did you connect the clock crystal and its associated components? That might be important. – Elliot Alderson Feb 22 '22 at 17:06
  • @ElliotAlderson I did. You can see it on the page 1 of the schematic section C1-2 as well as top right of the RP2040 on the PCB layout. – Agriculex Feb 22 '22 at 17:12
  • Can you re-upload the images and make them larger? They're fuzzy and difficult to read. – Aaron Feb 22 '22 at 19:06
  • @Aaron I added a G Drive link at the bottom to download and view the photos and schematic in original size. – Agriculex Feb 22 '22 at 21:13
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    A simple technique for determining if the pad is connected on an ic is to use the diode function on your multimeter. Assuming the ic has at least one 0V pad connected you should be able to measure the substrate diode for each pad. You can quickly determine if your USB signals are connected to the chip. With QFN, frequently I was convinced the pad was connected visually, but the diode test told me otherwise. – Kartman Feb 22 '22 at 21:23
  • I'd suggest you test your PCB with a multimeter. Check if there is a short circuit anywhere. Maybe there is a broken trace somewhere. You can find out that too. Here is another board design featuring RP2040. You can see this for references: https://www.pcbway.com/project/shareproject/AS2040_Rp2040_microcontroller_8821b499.html – liaifat85 Jul 26 '23 at 09:10

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