Hi @vivekbhadra ,
- No, USB connected to the Main board is fine.
- No, but if the SD card is fine, and works in a computer, has FAT filesystem and still doesn't work with Spresense, try with a different Spresense if you have a different one.
- I am using master too.
You will get the same config as I if you just:
tools/config.py -k release tools/config.py examples/camera
I don't think that the CONFIG_CXD56_SPISD has to be set since the SD card is not running on a regular SPI bus but the SDIO bus.
Press the main board to the extension board again if you can, maybe the connection is not proper in the B2B connector.
I can also email you my nuttx.spk file I used when I tested this. You can just flash that one down and see. Then you will have the exact same binary as I did and that has been proven to work.