ESP32 not detected over USB

[ssullivan]

Hello!
For my first SMD project, I've been designing a board that can read from an IMU at a fixed rate, and broadcast the reading over a CANbus. I finalized the design and populated the PCB and plugged it into my computer, but the ESP32 isn't detected at all.

I have added a 1uF capacitor the the CHIP_PU pin as per the datasheet (not shown in this schematic), and when that didn't work, shorted the CHIP_PU while powering up the board.

I've also checked that VCC to the board is a stable 3.266v

One interesting clue is that the LED on the board is dimly lit as soon as you plug it in, and if you short the CHIP_PU to ground, the LED turns off.

I know it's a long shot but if anyone would be willing to look over the schematic and tell me where I might have gone wrong, that would be awesome!

Thanks!

CAN IMU board.png (224.28 KiB) Viewed 197 times

[Sprite]

You're missing half the voltage rails: the chip won't work if you don't also power it via VDD3P3_RTC and VDD3P3_CPU. In general: always check the datasheet and the hardware design guidelines on how to connect an ESP32 and how to do the PCB design for it. For instance, aside from the fact that your reset circuit is incomplete (which you already noticed), you're also missing a decoupling cap on VDD_SPI. Aside from that, I'd make sure U0TXD, U0RXD and GPIO0 are accessible (e.g. on testpoints), as these can be invaluable during bringup of the chip.

[ssullivan]

Ha! I thought it must be something silly like that. I can add all of those changes.
Was going to ask just to be sure though, will this chip come with the firmware needed to flash via USB?

[Sprite]

Yes, ESP32 chips come with a bootloader in ROM. As I said, make sure GPIO0 is accessible, though, depending on the setup of your PC it may be easiest to ground that to force the chip into bootloader mode for the initial flash.

[ssullivan]

Great! Thank you so much for your help. I've fixed all those problems and ordered a new board