Update documentation on how to use SD

Author: sebromero

libraries/Nano33_System/examples/Nano33_updateBLandSoftDevice/Nano33_updateBLandSoftDevice.ino

@@ -1,13 +1,38 @@
 /*
- *  This sketch allows to support Soft Devices on Nano 33 BLE.
+ *  This sketch allows to support Soft Devices on the Arduino Nano 33 BLE (Sense).
  *  
  *  To be able to support Soft Devices, the bootloader first needs to be updated.
- *  Upload this sketch on the Nano 33 BLE to download the new bootloader in the flash. 
- *  After flashing the bootloader the sketch asks if you want to upload a SoftDevice.
- *  This is required for the OpenMV firmware to work.
- *  
  *  The new bootloader is fully backwards compatible with standard sketches.
+ *  -----------------------------------------------------------------------
+ * 
+ * INSTRUCTIONS
+ * 
+ *  1)  Upload this sketch on the Nano 33 BLE to download the new bootloader into the flash. 
+ *      You can choose whether to update only the bootloader or the bootloader plus SoftDevice.
+ *      Make a choice through the Serial monitor.
+ * 
+ *  2) After flashing the bootloader the sketch asks if you want to upload the SoftDevice.
+ *     This is required for the OpenMV firmware to work.
+ *     After completion, the board will reboot and enter the bootloader mode.
+ *
+ *  3) Now you can upload a sketch that uses the SoftDevice at 0x26000, using the following bossac command
+ *
+ *      /path/to/bossac -d --port=yourPort --offset=0x16000 -U -i -e -w /path/to/sketch.bin -R
+ *
+ *    Or you can still upload a standard sketch from the IDE at 0x10000. This will of course overwrite the SoftDevice.
+ *    So if you want to run a SoftDevice-related sketch, always remember to upload this sketch before and re-flash the SoftDevice.
+ *
+ *  To create a custom SoftDevice follow this procedure:
+ *
+ *  1) Convert your SoftDevice binary to a SoftDevice.h .
+ *    The nRF5-SDK website provides a SoftDevice.hex, so run the following commands:
+ *
+ *      objcopy --input-target=ihex --output-target=binary --gap-fill 0xff SoftDevice.hex SoftDevice.bin
+ *      xxd -i SoftDevice.bin > SoftDevice.h
  *
+ *  2) Copy the content of the generated header file to SoftDevice.h
+ * 
+ *  3) Run this sketch again and flash the SoftDevice.
  */
 
 #include "FlashIAP.h"