adamfeuer opened a new pull request #1393:
URL: https://github.com/apache/incubator-nuttx/pull/1393
## Summary
- SDMMC peripheral support for SAMA5D2 series microprocessors from Microchip
- provides an MMC/SD Card driver that works for reading and writing
- UHS_SDR50, UHS_DDR50, and UHS_SDR104 high-speed modes are supported, with
read/write speeds of 400Mbit/s in UHS_DDR50 (50MHz Double Data Rate) mode.
- This is a port of the NuttX imxrt_usdhc.c driver, as the SDMMC peripheral
uses a similar Cadence IP block.
- Basic instructions are in the README.txt.
## Impact
- None if you don't enable the SDMMC peripheral using the Kconfig system.
- Enables reading and writing to MMC or SD Cards. Only SD Cards have been
tested.
- VFAT filesystem has been tested and works. On the SAMA5D2-XULT board,
reading and writing to a bootable SD Card is supported.
## Testing
- Only tested on the SAMA5D2-XULT board from Microchip.
- Only manual read and write testing on a VFAT-formatted memory card
has been done.
- Driver was developed with extensive use of a logic analyzer to ensure
the SDMMC driver was functioning correctly.
- Only UHS_DDR50 mode was tested, as all my SD Cards support only that.
## How to Test
1. Format an SD Card with VFAT format.
1. Put some text files on the card.
1. Insert the card into the SAMA5D2-XULT SD Card slot.
1. Build the sama5d2-xult:sdmmcnsh configuration
1. Load NuttX onto the board
1. /mnt/mmcsd1 should have your files. You can cd, ls, cp, rm, and cat
to test the filesystem.
## TODO / Limitations
- e.MMC should work, but was not tested
- Performance tests have not been done
- UHS_SDR50 and UHS_SDR104 modes were not tested as I don't have any
SD Cards that support those modes.
## Notes
- nxstyle shows some formatting errors, but I couldn't find good ways
to make them go away without mangling the files. I welcome ideas on
how to better format the code so nxstyle passes!
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