@Tim Edwards the spi on caraval and vddio, can it be scaled down to 1.8V? I see the ftdi chip uses spi for 3.3V but my communication with chip is happening at 1.8V logic using a fpga

vddio

can be dropped to 1.8V and the chip is supposed to work; I have dropped it to around 2.3V and could get it to continue working. Below that and other circuits on the board start dropping out. I have not looked at the absolute maximum (or rather minimum) ratings of the various chips. It's possible that the LDO is the first to drop out, which would mean you might be able to bring the voltage down further if you supply both the

vddio

and

vccd

supplies externally instead of relying on the LDO (note that the rev 5A board has a chip U4 on it which is a POR with a 3V threshold and prevents anything from operating at less than 3V unless you remove the chip and bypass the reset button). There are also options on the GPIO for changing the threshold voltage. You might be able to maintain 1.8V communication with the chip by setting the input buffer trip voltage appropriately (or possibly it works as-is), and set SDO to be an open-drain configuration that you can pull up to 1.8V with a resistor so that it doesn't try to drive 3.3V into your FPGA.

@Tim Edwards so only vddio needs to be dropped to 1.8V? How about vccd2/1 and vdda2/1. I made all 1.8 V , disconnected LDO and gave external 1.8 V

You will not be able to run the FTDI and flash at 3.3V while the Caravel part has a VDDIO of 1.8V, or you will forward-bias the ESD diodes and dump a huge amount of current. You would need to have a level shifter between the parts running at 3.3V and the Caravel chip running at 1.8V. You might be able to get by with the other parts running at 2.3V, as that is right at the ESD diode threshold so probably not dumping enough current to worry about, but running the system at the edge of failure isn't a great idea.

Then what about flash? Which is also at 3.3V @Tim Edwards and it’s also on spi with chip with vddio 1.8V

Anything connected to the Caravel chip pins should not be forward-biasing into the ESD diodes, and that includes the SPI flash chip, the FTDI chip, and the clock chip. The reset pin and gpio (LED) are grounded on the other side so they don't need to be a concern.