Ok, for NanoVNA V2 SD card support need:
Use RTC for auto file name, RTC on default V2 used in bootloader, so have limits (restart on power on, slow tick), better update bootloader, but at this moment leave it
Second need install SD card slot to V2 board:
SD card use SPI bus for data exchange (shared vs LCD), so need connect:
CPU SD Card
PB5(MOSI) <--> 3 (SD card DI)
PB4(MISO) <--> 7 (SD card DO)
PB3(SCLK) <--> 5 (SD card SCLK)
PB9(CS) <--> 2 (SD card CS)
And power/gnd pins
3.3V <--> 4 (SD card Vdd)
GND <--> 6 (SD card GND)
And flash this firmware
you see additional menu SD CARD, in it possible save screenshots, and s1p/s2p files
PS i test it on test board vs GD32 CPU, should work
PSS attach V2 schemantic and SD card info
PSS in all cases better instal/remove SD card if device power off (on insert possible voltage drop, add 10 Om resistor in middle 3.3V and SD card Vdd can help)
