Flashsize_F103: Options for BMP on STM32F103C8 devices

src/platforms/stlink/Flashsize_F103

@@ -24,16 +24,30 @@ Ignoring the chip marking and using an F103C8 blindly as a F103Cb is done
 already with few problems on many china boards (e.g. blue pill). Probably
 this second approach will work for many of the older STLinks.
 
-Use at your own risk!
+dfu-util cares for the size and refuses to programm above the announced size:
+ > dfu-util -S E4D078EA -s 0x08002000:leave -D blackmagic.bin
+ dfu-util 0.9
+ ...
+ dfu-util: Last page at 0x0801093f is not writeable
 
-With DFU upload available in the bootloader, you can verify by uploading the
-binary from flash and comparing it against the binary downloaded.
-- Download new BMP binary (if not already done)
-  dfu-util -s 0x08002000:leave:force -D blackmagic.bin
-- Get length of binary
+Flash above the announced size with recent bootloader/BMP:
+==========================================================
+script/stm32_mem.py does not care for the announced size:
+ > ../scripts/stm32_mem.py blackmagic.bin
+ ...
+ USB Device Firmware Upgrade - Host Utility -- version 1.2
+ ...
+ Programming memory at 0x08010800
+ All operations complete!
+
+Get length of binary
   > ls -l blackmagic.bin
-  -rwxr-xr-x 1 bon users 57372 15. Apr 14:17 blackmagic.bin
-- Upload binary from flash
-  > dfu-util -s 0x08002000:leave:force:57372 -U blackmagic.bin.1
-- Compare
+ -rwxr-xr-x 1 bon users 59712 21. Sep 22:47 blackmagic.bin
+Actual file size may differ!
+
+Upload binary from flash with the exact size
+  > dfu-util -s 0x08002000:leave:force:59712 -U blackmagic.bin.1
+
+Compare
   > diff blackmagic.bin*
+No differences should get reported!