Spartan Edge Accelerator standalone startup

Hi.



It seems the ESP32 doesn’t start automatically on power up.

It does start after quite a few presses on RST button.

But it looks like it starts immediately when terminal app is connected to the usb-uart port.

I’ve tried both - powering via usb cable from a laptop usb port or from a charger, and using a PSU to supply voltage to VIN pin.



Is that a design choice to stall the ESP until there’s a connection to onboard usb uart, or some issue?

Ok, it’s not about ESP32 startup.



I was watching the FPGA_DONE led to see when fpga will be configured, and it never did upon startup. So I concluded (incorrectly) ESP is at fault, not starting properly. I had no other suspects, because as soon as I connect to uart with some terminal app, I see the normal bootup sequence, followed by correct initialization of FPGA.



But I noticed that normal sketch ‘01LoadDefaultBitstream’ fails every other reset because SD card couldn’t be mounted.

Pressing reset button many times I see one time it fails, second time runs ok, third time fails, fourth time ok, and so on.



So I’ve excluded SD card from the picture by embedding the fpga bitstream into ESP32 program body.

Now I see fpga configured every time the board is powered, and the issue must be related to SD card handling.

Mounting fails upon power on, and the uart connection resets the board, so this second time SD card is mounted ok, and I couldn’t see earlier messages about failed mounting.