I'm waiting for my de10 nano to come in the mail. I was thinking about doing this, but i only have an sd card slot, would i be able to wire it directly to the gpio pins or do i need to buy a arduino module like you have in the picture?
Also that you for the great pictures. Thank you sorgelig for creating and maintaining the mister project!
Direct pin connections will be sufficient. Arduino module isn't required. Note: you will need to connect VCC pin of naked SD card to 3.3v! not 5V. Otherwise you will damage your SD card. Arduino shield uses 5v-to-3.3v converter.
Although, currently secondary SD is used in SPI mode, it's possible that future cores will use native SD interface and this connection won't work. But since it's DIY you will only need to connect remaining pins when it will be required. Just saying.
P.S.: do not use too long wires. It may affect the SD card work on high speeds.
Nope. Secondary SD card is a bare connection to FPGA, so core manage SD interface by itself. USB is not connected to FPGA and has completely different protocol. So, you cannot replace SD card by USB card reader.
But you can connect some arduino SD module to GPIO connector as shown above. You don't need I/O board for that.