bootloader: README updates for PIC32 bootloader

Author: signal11

apps/bootloader/README.txt

@@ -1,9 +1,9 @@
 
-PIC24 Bootloader
-=================
+PIC24F/32MX Bootloader
+=======================
 
-This is the PIC24 USB bootloader. It contains firmware and software to
-implement a USB bootloader using M-Stack.  It differs from the Microchip
+This is the PIC24F/32MX USB bootloader.  It contains firmware and software
+to implement a USB bootloader using M-Stack.  It differs from the Microchip
 bootloaders in several key ways in both licensing and implementation.
 
 License
@@ -12,6 +12,16 @@ Like the rest of M-Stack, this bootloader is free software, and its firmware
 and software are usable under the terms of either the LGPL version 3, or the
 Apache License, version 2.0.
 
+The Linker scripts for the PIC24 come from the PIC Linker Script Generator
+(linked below) and have a permissive license. See the file header for the
+included linker scripts.
+
+The PIC32 linker scripts are derived from the Linker scripts which are
+distributed with the XC32 toolchain, version 1.40.  These linker scripts are
+copyrighted by Microchip and are used under a BSD-style license.  See the
+file header on these scripts for details.  This is separate from the license
+of M-Stack.
+
 Firmware Implementation
 ------------------------
 This bootloader's implementation does not use HID, as the Microchip
@@ -20,25 +30,27 @@ difference makes this bootloader faster, and gives it a more robust
 interface, since control transfers can be rejected by the firmware if they
 are not correct.
 
-Another difference from the Microchip bootloader is that it uses linker
-scripts from the Signal 11 PIC Linker Script Generator at
-https://github.com/signal11/pic_linker_script .  The generated scripts make
-use of both the C preprocessor and more advanced linker script features to
-create linker scripts which can be used in the same form for both the
-bootloader and the application to be loaded by the bootloader.  This way
-only a single linker script is needed for both projects (bootloader and
-application) which is less prone the inherent errors of manual edits.  A
-single #define in the MPLABX project is used to select whether the linker
-script is being used for the bootloader or for the application (define
-either BOOTLOADER or BOOTLOADER_APP to select the mode).  See the PIC Linker
-Script Generator README for more details.
+Another difference from the Microchip bootloader is that for PIC24F it uses
+linker scripts from the Signal 11 PIC Linker Script Generator at
+https://github.com/signal11/pic_linker_script .  The generated scripts for
+PIC24F and the hand-modified scripts for PIC32MX make use of both the C
+preprocessor and more advanced linker script features to create linker
+scripts which can be used in the same form for both the bootloader and the
+application to be loaded by the bootloader.  This way only a single linker
+script is needed for both projects (bootloader and application) which is
+less prone to the inherent errors of manual edits.  A single #define in the
+MPLABX project is used to select whether the linker script is being used for
+the bootloader or for the application (define either BOOTLOADER or
+BOOTLOADER_APP to select the mode).  See the PIC Linker Script Generator
+README for more details.
 
 Also different in the implementation is that the linker script passes flash
 addresses to the bootloader firmware.  This means that for MCUs with the
-same flash layout (such as the entire PIC24F family), the bootloader
-firmware and software source code does not have to change between different
-MCUs.  Only the linker script does, with data that comes directly from the
-datasheets.
+same flash layout (such as the entire PIC24F family and the entire PIC32MX
+family), the bootloader firmware and software source code does not have to
+change between different MCUs.  Only the linker script does, with data that
+comes directly from the datasheets.  This means there are no #defines in the
+source code with memory addresses and ranges for each MCU.
 
 Software Implementation
 ------------------------
@@ -50,9 +62,10 @@ Supported Platforms
 --------------------
 Currently tested platforms are:
 	PIC24FJ64GB002
+	PIC32MX460F512L (PIC32 USB Starter Board)
 
-In theory, any PIC24F MCU should work as long as a suitable linker script
-is made.
+In theory, any PIC24F or PIC32MX MCU should work as long as a suitable
+linker script is made.
 
 Contributing
 -------------
@@ -65,7 +78,6 @@ Future Plans
 Future goals include the following:
 	* More PIC24F platforms
 	* PIC16F PIC18F PIC24E, dsPIC33E
-	* PIC32
 Note that the USB stack will first have to be ported to several of those
 platforms before te bootloader can be ported. Patches are welcome.