Update README.md

Author: mohitbhoite

README.md

@@ -1,5 +1,88 @@
 # Spark STM32 Bootloader
 
-Careful!  Low level dragons here!
+*Careful!  Low level dragons here!*
 
-Real README content in the near future. ;-)
+  * Really make sure you have a working programmer shield and an ST-link programmer.
+  * Is this a brand new core from scratch (that you made? nice!) goto 1, or is it this a core that came from Spark - goto "unlocking your bootloader"
+
+### Unlocking your bootloader
+
+Welcome! The bootloader on the stm32 is protected by a "write protect" flag that helps prevent accidental "bricking" of a core for those without a programmer shield / st-link programmer. But that's not you, you want to fully erase your core, or re-write your bootloader, and you're not scared of "bricking" anything.
+
+ * Grab the "unlocker" from here: (https://github.com/spark/bootloader/tree/master/tools (use "raw")
+ * dfu that with a:  `dfu-util -d 1d50:607f -a 0 -s 0x08005000:leave -D unlocker-firmware.bin`
+ * Your core should restart, flash some lights, and end with a 'green' flash before wiping saved wifi profiles and resetting   
+ * Your bootloader is unlocked!
+
+**1. Make sure you have st-flash installed, or have a copy of the ST-Link Utility software.**
+
+ * You can find the software on their site if you're using windows: http://www.st.com/web/catalog/tools/FM146/CL1984/SC724/SS1677/PF251168 
+
+ * If you're on mac / linux grab "st-flash" you can grab and build a tool yourself:
+    ```
+    git clone [email protected]:texane/stlink.git
+    cd stlink
+    ./autogen.sh
+    ./configure
+    make
+    make install
+    ```
+    
+**2. Grab a copy of the latest bootloader from here:**
+
+  https://github.com/spark/bootloader/blob/master/build/bootloader.bin?raw=true5.) With your core in your programmer shield / st-link connected, lets re-flash some stuff!
+
+ * In the windows utility set device -> settings to "connect under reset" true! (if you can't find this that's okay)
+ * Do a full erase of your core, do this a few times, if you're in the windows utility, view the memory and make sure it's zero-ed out.
+ * Write your bootloader.bin back to 0x08000000
+ * Congrats, you re-wrote your bootloader!
+
+**3. Lock your bootloader back up! (Optional, but recommended)**
+
+ * Grab the locking firmware here:  (https://github.com/spark/bootloader/tree/master/tools (use "raw")
+ * dfu that to `dfu-util -d 1d50:607f -a 0 -s 0x08005000:leave -D locker-firmware.bin`
+ * your core should reset, flash some lights, and flash 'red' when locked.
+
+**4. Okay, lets keep going and update the radio driver on the CC3000**
+
+ * Grab the patch programmer from here: https://github.com/spark/cc3000-patch-programmer/blob/master/build/cc3000-patch-programmer.bin?raw=true
+ * dfu it with: `dfu-util -d 1d50:607f -a 0 -s 0x08005000:leave -D cc3000-patch-programmer.bin`
+ * hold down the mode button for 3+ seconds until the light starts blinking, let your core sit for 20-60 seconds after the light stops blinking.
+ * At this point you can erase your core with the st-link programmer (did you lock your bootloader?), to get it back into dfu mode
+
+
+### It's time to write some stuff to external flash!
+
+ **1. Lets make some keys (optional step if your keys have been fine):**
+ 
+```
+    openssl genrsa -out core.pem 1024
+    openssl rsa -in core.pem -pubout -out core_public.pem
+    openssl rsa -in core.pem -outform DER -out core_private.der
+```
+    
+ **2. Flash your new private key:** 
+ 
+    `dfu-util -d 1d50:607f -a 1 -s 0x00002000 -v -D core_private.der`
+    
+ **3. Grab the server public key, and flash it:**  
+    https://s3.amazonaws.com/spark-website/cloud_public.der
+    
+    `dfu-util -d 1d50:607f -a 1 -s 0x00001000 -v -D cloud_public.der`
+
+ **4. Grab the latest firmware and flash it**  
+ 
+    https://github.com/spark/core-firmware/blob/spark_2/build/core-firmware.bin?raw=true
+    
+```
+    # to the factory reset spot 
+    dfu-util -a 1 -s 0x00020000 -v -D core-firmware.bin
+
+    ## to the main firmware spot
+    dfu-util -a 0 -s 0x08005000:leave -D core-firmware.bin
+```
+    
+ **5. If you made new keys, be sure to send someone at Spark your new public key, along with your core id, otherwise your core won't connect to the cloud again!**
+ 
+ *(Thanks to David for putting this together)*  
+ Ref: https://community.spark.io/t/st-link-programmer-shield-only-so-youve-decided-you-want-to-update-your-bootloader-and-everything/2355