[FAQ] J721S2XSOMXEVM: EMMC Boot Partition Switching in keywriter application

Step 1: Apply the Patch

https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/791/mmcsd_5F00_kw.patch

Apply the `mmcsd_kw.patch` to your keywriter source code:

cd /path/to/pdk/packages/ti/boot/keywriter
git apply mmcsd_kw.patch

Or manually apply the changes from the patch file.

Step 2: Select Target Partition

Open `main.c` and locate (after applying the patch):

int32_t status = CSL_EFAIL, retVal, partition = 1;
```

Modify the `partition` variable:
- **For boot0**: Set `partition = 1`
- **For boot1**: Set `partition = 2``

Step 3: Rebuild Keywriter Application

cd <RTOS_SDK>/<PDK>/packages/ti/build
make keywriter_img_clean  BOARD=<BOARD_NAME> 
make keywriter_img  BOARD=<BOARD_NAME>

Step 4: Deploy and Run

1. Flash the rebuilt keywriter binary to your target device
2. Run keywriter application
3. Monitor UART output for partition switching confirmation.