Hi all, From my understanding Caravel bootloader takes the executable from an external spi flash and then copies it to internal sram and then runs from there. Once the chip comes, will the test board provide necessary hw to flash an bin file into the spi flash ?. Please correct me if I am wrong. Also what would be the on board connected clock frequency to the Caravel SoC ?

yes, it will have USB FTDI interface that can program the flash via the managment area of the caravel soc

Thanks🙂

@Siva Prasad: It is not a bootloader per se, although it can be done that way. Normally the program runs directly off of the SPI flash, not from SRAM (which is pretty limited). The program can configure the SPI flash for quad DDR mode, which should be able to read only (I think) 4x slower than it would read the program from SRAM. The external clock we use on the boards is 10MHz, although if you switch to the DLL, you should be able to drive the processor at 50MHz, which is what it was designed to.

Oh is it like xip mode in flash . Execute in place , directly from flash ? . How can we configure the DLL ?

@Moataz Alaa @Rawan Adel

@Siva Prasad: I have documentation on the DLL somewhere in the caravel repository under docs/, I think, unless somebody removed it. It is pretty straightforward, with a feedback divider and an output divider, that can be programmed through the SPI. There is also a mode for the SoC to drive the SPI to change the same settings, but the settings themselves are part of the SPI.