Pull request #25: Add S1 for reentry into the bootloader

Merge in MCU16CE/dspic33-dsc-bootloader-code-examples from ~C74569/dspic33-dsc-bootloader-code-examples:feature/MCU16GITHUB-933-add-button-re-entry-into-bootloader to develop

* commit 'e27ae0a7543e80fd57bb4eff03cc5f27dc15afb8':
  Center arrow in image and remove white spaces in Readme
  Add S1 for reentry into the bootloader

Author: aiwyatt787

secure_boot_and_secure_firmware_upgrade_over_canfd/README.md

@@ -113,6 +113,14 @@ The associated bootloader and application projects demonstrate the following:
     a. After a few seconds, LED11 should be blinking<br>
 ![Program Device](./images/UBHA_Program.png)
 
+#### Re-Entering Bootloader Mode
+1. Power off the board by unplugging the micro-USB cable from port J1
+2. While the board is powered off, hold down switch S1<br>
+![S1](./images/switch_location.png)
+3. Continue holding down S1 and plug the micro-USB cable back into port J1
+4. Once the board is powered back on, release S1
+5. Verify LED11 is solid, indicating the device is in bootloader mode. The application can now be loaded once again (see Loading the Application) 
+
 ## Trademarks
 
 MPLAB® is a registered trademark of Microchip Technology Inc. All other trademarks are the property of their respective owner.

secure_boot_and_secure_firmware_upgrade_over_canfd/boot.X/boot.mc3

@@ -60,6 +60,7 @@ Copyright (c) [2012-2024] Microchip Technology Inc.
 #include "boot_application_header.h"
 #include "boot_image.h"
 #include "boot_process.h"
+#include "../mcc_generated_files/system/pins.h"
 #include "../mcc_generated_files/timer/mccp9.h"
 
 #define DOWNLOADED_IMAGE    1u
@@ -216,5 +217,5 @@ static bool EnterBootloadMode(void)
     /* NOTE: This might be a a push button status on power up, a command from a peripheral, 
      * or whatever is specific to your boot loader implementation */    
 
-    return false;
+    return (IO_RD13_GetValue()==0);
 }

secure_boot_and_secure_firmware_upgrade_over_canfd/boot.X/mcc_generated_files/boot/boot_demo.c

@@ -94,6 +94,57 @@
  */
 #define IO_RA6_SetDigitalOutput() (_TRISA6 = 0)
 
+/**
+ * @ingroup  pinsdriver
+ * @brief    Sets the RD13 GPIO Pin which has a custom name of IO_RD13 to High
+ * @pre      The RD13 must be set as Output Pin             
+ * @param    none
+ * @return   none  
+ */
+#define IO_RD13_SetHigh()          (_LATD13 = 1)
+
+/**
+ * @ingroup  pinsdriver
+ * @brief    Sets the RD13 GPIO Pin which has a custom name of IO_RD13 to Low
+ * @pre      The RD13 must be set as Output Pin
+ * @param    none
+ * @return   none  
+ */
+#define IO_RD13_SetLow()           (_LATD13 = 0)
+
+/**
+ * @ingroup  pinsdriver
+ * @brief    Toggles the RD13 GPIO Pin which has a custom name of IO_RD13
+ * @pre      The RD13 must be set as Output Pin
+ * @param    none
+ * @return   none  
+ */
+#define IO_RD13_Toggle()           (_LATD13 ^= 1)
+
+/**
+ * @ingroup  pinsdriver
+ * @brief    Reads the value of the RD13 GPIO Pin which has a custom name of IO_RD13
+ * @param    none
+ * @return   none  
+ */
+#define IO_RD13_GetValue()         _RD13
+
+/**
+ * @ingroup  pinsdriver
+ * @brief    Configures the RD13 GPIO Pin which has a custom name of IO_RD13 as Input
+ * @param    none
+ * @return   none  
+ */
+#define IO_RD13_SetDigitalInput()  (_TRISD13 = 1)
+
+/**
+ * @ingroup  pinsdriver
+ * @brief    Configures the RD13 GPIO Pin which has a custom name of IO_RD13 as Output
+ * @param    none
+ * @return   none  
+ */
+#define IO_RD13_SetDigitalOutput() (_TRISD13 = 0)
+
 /**
  * @ingroup  pinsdriver
  * @brief    Sets the RD15 GPIO Pin which has a custom name of IO_RD15 to High

secure_boot_and_secure_firmware_upgrade_over_canfd/boot.X/mcc_generated_files/system/pins.h

@@ -100,7 +100,7 @@ void PINS_Initialize(void)
     ANSELA = 0x001F;
     ANSELB = 0x039E;
     ANSELC = 0x00CF;
-    ANSELD = 0x2C00;
+    ANSELD = 0x0C00;
     ANSELE = 0x000F;
     ANSELF = 0x03C0;