Using SD0 for a bootable SD card slot.
Posted: Thu Aug 25, 2016 9:25 pm
I would like to create a battery powered device that has wifi and expandable storage. USB should be avoided because it is very power inefficient, especially when compared to SDIO wifi and SD cards. UART, SPI, and other interfaces are too slow for the desired transfer speeds.
The main problem I face is that the BCM283x family only supports two SDIO buses and one of them is already in use by the internal NAND flash. 4GB isn't very preferable for my intended device so the NAND flash does little for me. Is it possible to disable the NAND flash and boot from an SD card that is connected to the SD0 bus similar to those used by other Raspberry Pi models? I figure that it probably isn't, but it can't hurt to ask.
I would use the Zero for this project, but I need GPIO's 28-45 for this project as well. It is such a pity they weren't broken out on the Zero.
Edit1: If this isn't possible then is it feasible to use the USB bus for an SD Card slot with some kind of USB-SD interface IC?
The main problem I face is that the BCM283x family only supports two SDIO buses and one of them is already in use by the internal NAND flash. 4GB isn't very preferable for my intended device so the NAND flash does little for me. Is it possible to disable the NAND flash and boot from an SD card that is connected to the SD0 bus similar to those used by other Raspberry Pi models? I figure that it probably isn't, but it can't hurt to ask.
I would use the Zero for this project, but I need GPIO's 28-45 for this project as well. It is such a pity they weren't broken out on the Zero.
Edit1: If this isn't possible then is it feasible to use the USB bus for an SD Card slot with some kind of USB-SD interface IC?