5.2 Creating an Application

With the bootloader code built and configured to the needed specifications, configure the target application to work alongside the bootloader instead of erasing the bootloader code from the device and programming the new target application over it. MPLAB X IDE allows the user to set various project configuration properties to match the bootloader configuration. The first step for completing this task is to create a blinking LED project.

  1. Create a new MPLAB X IDE project.

    Figure 5-41. New Application Project
  2. MCC opens up automatically when a new project is created. If not, click the MCC button in the menu bar to start the MPLAB Code Configurator.
    Figure 5-42. Open MCC

  3. Configure the on-board LED by setting the RF3 pin. Set the Custom Name to LED.

    Figure 5-43. LED Configuration
  4. Add the Delay driver from Device Resources>Drivers>Timer to the project.
    Figure 5-44. Delay Driver

  5. Press the Generate button in the Project Resources tab to generate the project code.

    Note: Make sure to match the Clock Control and Configuration Bits settings to the bootloader project settings.
    Figure 5-45. Generate Application Code

  6. For a blinking LED application, add the following code to main.c in Source Files under the project folder. The delay.h header file must also be included in the main file.

    Figure 5-46. Blinking LED Code
  7. Add the following code at the top of the main.c file before the main function. This reserves the last bytes to hold the Checksum value. The address presented below in the __at() is PROGMEM_SIZE - 2, since the Checksum hash size used is two bytes. For PIC16 devices, this address is in words.
    Note: For Checksum, CRC16 and Check State Flag verification schemes, the hash size is two bytes. For CRC32, the hash size is four bytes.

    Checksum Verification Scheme

    #include <stdint.h> 
#ifdef __XC8__ 
#include <xc.h> 
#endif 
volatile const uint16_t 
#ifdef __XC8__ 
__at(0x1FFFE) 
#endif 
applicationFooter __attribute__((used, section("application_footer"))) = 0xFFFF;

    CRC32 Verification Scheme

    #include <stdint.h> 
#ifdef __XC8__ 
#include <xc.h> 
#endif 
volatile const uint32_t 
#ifdef __XC8__ 
__at(0x1FFFC) 
#endif 
applicationFooter __attribute__((used, section("application_footer"))) = 0xFFFFFFFF;

    CRC16 Verification Scheme

    #include <stdint.h> 
#ifdef __XC8__ 
#include <xc.h> 
#endif 
volatile const uint16_t 
#ifdef __XC8__ 
__at(0x1FFFE) 
#endif 
applicationFooter __attribute__((used, section("application_footer"))) = 0xFFFF;

    Check State Flag Verification Scheme

    #include <stdint.h> 
#ifdef __XC8__
#include <xc.h> 
#endif
volatile const uint8_t 
#ifdef __XC8__ 
__at(0x1FFFE) 
#endif 
applicationFooter __attribute__((used, section("application_footer"))) = 0x55;
    Figure 5-47. Add Verification Settings in main.c

  8. Configure the project properties. Go to File>Project Properties and select PIC18F57Q43 Curiosity Nano under Connected Hardware Tool, DFP version under Packs and the XC8 version under Compiler Toolchain.

    Figure 5-48. Set Project Properties
  9. Configure the linker setting for the used verification scheme before proceeding to the next step in compiling the project.
    Note: Check out the Compiler and Linker Settings section below for details on the configuration for PIC and AVR devices.
  10. Click Clean and Build to the generate the project hex file.

Compiler and Linker Settings

PIC

The following section is intended to provide an explanation of the compiler and linker settings utilized in the PIC18F57Q43 end application project. The example below uses the Checksum verification scheme for demonstration.

  • Linker → Additional Options
    • Codeoffset = 2000h
    • Checksum = 2000-1FFFD@1FFFE,width=-2,algorithm=2

Here,

  • 2000 → Bootloader offset value

  • 1FFFD → Program Memory Size

  • Width → Width of Checksum – This value is used because the checksum calculated is two bytes and it will occupy the last two bytes of the Program Memory. For CRC32, the Cyclic Redundancy Check (CRC) value is four bytes and for CRC16, the CRC value is two bytes.

  • 1FFFE → Checksum value will be stored here for two bytes

  • Algorithm → Checksum verification schemes algorithm value

  • Polynomial → Hexadecimal value used when calculating CRC. Refer to the Verification Schemes section for more information.

    Linker Additional options setting for the verification schemes:

  • CRC16 → 2000-1FFFD@1FFFE,width=-2,algorithm=5,offset=FFFF,polynomial=1021

  • CRC32 → 2000-1FFFB@1FFFC,width=-4,algorithm=-5,offset=FFFFFFFF,polynomial=04C11DB7

  • Checksum → 2000-1FFFD@1FFFE,width=-2,algorithm=2

Figure 5-49. Project Properties - Checksum Configuration

Open File>Project Properties. Add the below settings to the XC8 Linker>Fill Flash Memory. These steps enable the mentioned sequence to fill all the unused memory space in the generated hex file. Set the Memory address range to Application Start Address:End of Flash Memory.

Note: In case of PIC16 devices, the value in the field Sequence should be 0x3FFF.
Figure 5-50. XC8 Linker - Fill Flash Memory

AVR

For AVR devices, a batch file execution is enabled in the Project Properties to fill the empty spaces in the application project with a given sequence. Follow the steps below to create the batch file.

  1. Right click the Source Files>New>Other.
    Figure 5-51. New Linker File
  2. In the New File window, select Other under Categories and Empty File under File Types. Click Next.
    Figure 5-52. New File Window
  3. In the File Name text box, enter postBuild.bat as the file name and click Finish.
    Figure 5-53. New postBuild.bat File
  4. Add the following lines to the postBuild.bat file to configure the application section based on the verification scheme selected.
    • For all verification schemes, to fill the unused space:
      hexmate r0-FFFFFFFF,%1 -O%1 -FILL=w1:0xFF@0x2000:0x1FFFF

      Here,

      0x2000 → Application Start Address

      0x1FFFF → Program Flash Memory Range End Address

    Checksum Verification
    • To perform the calculation and store the result: 
      hexmate %1 -O%1 +-CK=2000-1FFFD@1FFFEg2w-2

      Here,

      The application code can use memory addresses 0x2000-0x1FFFD. The 2-byte checksum value is placed at address 0x1FFFE.

    CRC16 Verification
    • To perform the calculation and store the results:
      hexmate %1 -O%1 +-CK=2000-1FFFD@1FFFE+FFFFg5w-2p1021
    CRC32 Verification
    • To perform the calculation and store the results:
      hexmate %1 -O%1 +-CK=2000-1FFFB@1FFFC+FFFFFFFFg-5w-4p04C11DB7
    Figure 5-54. postBuild.bat File
  5. With the postBuild script created, open Project Properties>Building. Enable the “Execute this line after build” checkbox. Add the following lines in the text box below it.
    postBuild${ShExtension} ${ImagePath}
    Figure 5-55. postBuild.bat File Execution

AVR - XC8 Compiler

Open Project Properties>XC8 Global Options>XC8 Linker>Additional Options. In the “Extra linker options” text box, add 
-Ttext=<Application Start Address> -Wl,-u,applicationFooter
Figure 5-56. XC8 Linker Settings - Additional Options

In XC8 Compiler-Preprocessing and messages, make sure to enable “Use CCI Syntax”.

Figure 5-57. XC8 Compiler Settings - Preprocessing and Messages

AVR - GCC Compiler

Figure 5-58. GCC Linker Settings - Memory Settings
Image File Generation

With the bootloader client and the application projects created, the image file can be generated by using the Firmware Image Builder ( pyfwimagebuilder) tool by combining the bootloader_configuration.toml file and the application hex file.

Note: The toml file will be inside Booloader Project Folder>mcc_generated files>bootloader>configurations, and the hex file is present at Application Project Folder>dist>default>production.
Command: 
pyfwimagebuilder build -i PIC18F57Q43_App.X.production.hex -c bootloader_configuration.toml -o output.img
Figure 5-59. Image File Generation

End Application Programming

The newly-generated application image can be transferred to the target device using the Microchip Device Firmware Update (pymdfu) tool.

Command:
pymdfu update --tool serial --image output.img --baudrate 9600 --port COM48
Figure 5-60. pymdfu Execution
Note: The above command is for UART communication. For SPI, refer to pymdfu section.