MCUboot based Basic Bootloader for PSoC 61

Disclaimer: This is a community code example (CCE) released for the benefit of the community users. These projects have only been tested for the listed BSPs, tools versions, and toolchains documented in this readme. They are intended to demonstrate how a solution / concept / use-case can be achieved on a particular device. For official code examples, please click here

This community code example (CCE) demonstrates the implementation of MCUBoot based bootloader for PSoC™ 61 MCU devices. This CCE is derived from mtb-example-psoc6-mcuboot-basic and PSoC61 support to run both Application and Bootloader from CM4 CPU is added.

In order to test this sample you need target board with PSoC61. You can replace the PSoC6 IC on one of the PSoC™ 6 development kits with PSoC™ 61 MCU IC.

Requirements

ModusToolbox™ software v3.0 (tested with MTB V3.0)
Board support package (BSP) minimum required version: 4.0.0
Programming language: C
Associated parts: PSoC™ 61 MCU Note: Only CY8C6136BZI-F34 is tested in this CCE.

Supported toolchains (make variable 'TOOLCHAIN')

GNU Arm® embedded compiler v10.3.1 (GCC_ARM) - Default value of TOOLCHAIN

Supported Kit

This code example uses a customized PSOC 62 KIT with PSoC™ 61 MCU IC mounted on it.
Any one of the PSoC™ 6 development kits can be used by replacing the IC on the board with PSoC™ 61 MCU IC. This document uses PSoC™ 62S2 Wi-Fi Bluetooth® pioneer kit (CY8CKIT-062S2-43012) with PSOC 61 CY8C6136BZI-F34 custom mounted on it as a reference for all the discussions

Note: Though this code example talks about customizing the CY8CKIT-062S2-43012, any other PSoC62 KIT can be used. Or user may decide to build his own KIT with PSoC61 and test this code example. Care must be taken to configure the BSP correctly in such cases. Please refer BSP Assistant User Guide to create your own BSP.

Before using this code example, make sure that the board is upgraded to KitProg3. The tool and instructions are available in the Firmware Loader GitHub repository. If you do not upgrade, you will see an error like "unable to find CMSIS-DAP device" or "KitProg firmware is out of date".

Software setup

Install a terminal emulator if you don't have one. Instructions in this document use Tera Term.

Python is shipped as part of the ModusToolbox™ installation. Add the python installation path from the ModusToolbox™ installation directory to the top of the system path in environmental variables.

Using the code example

It is recommended to use a new workspace. Create the project and open it using one of the following:

In Eclipse IDE for ModusToolbox™ software

Click the New Application link in the Quick Panel (or, use File > New > ModusToolbox™ Application). This launches the Project Creator tool.
Pick a kit supported by the code example from the list shown in the Project Creator - Choose Board Support Package (BSP) dialog.

When you select a supported kit, the example is reconfigured automatically to work with the kit. To work with a different supported kit later, use the Library Manager to choose the BSP for the supported kit. You can use the Library Manager to select or update the BSP and firmware libraries used in this application. To access the Library Manager, click the link from the Quick Panel.

You can also just start the application creation process again and select a different kit.

If you want to use the application for a kit not listed here, you may need to update the source files. If the kit does not have the required resources, the application may not work.

Note: In this step, please create the application picking a any known Kit like CY8CKIT-062S2-43012 This is because, there are no offcial PSoC™ 61 Kit and hence the BSP. You will have build your own BSP; which will be discussed in next steps.
In the Project Creator - Select Application dialog, choose the example by enabling the checkbox.
(Optional) Change the suggested New Application Name.
The Application(s) Root Path defaults to the Eclipse workspace which is usually the desired location for the application. If you want to store the application in a different location, you can change the Application(s) Root Path value. Applications that share libraries should be in the same root path.
Click Create to complete the application creation process.

For more details, see the Eclipse IDE for ModusToolbox™ software user guide (locally available at {ModusToolbox™ software install directory}/ide_{version}/docs/mt_ide_user_guide.pdf).

In command-line interface (CLI)

ModusToolbox™ software provides the Project Creator as both a GUI tool and the command line tool, "project-creator-cli". The CLI tool can be used to create applications from a CLI terminal or from within batch files or shell scripts. This tool is available in the {ModusToolbox™ software install directory}/tools_{version}/project-creator/ directory.

Use a CLI terminal to invoke the "project-creator-cli" tool. On Windows, use the command line "modus-shell" program provided in the ModusToolbox™ software installation instead of a standard Windows command-line application. This shell provides access to all ModusToolbox™ software tools. You can access it by typing modus-shell in the search box in the Windows menu. In Linux and macOS, you can use any terminal application.

This tool has the following arguments:

Argument	Description	Required/optional
`--board-id`	Defined in the `<id>` field of the BSP manifest	Required
`--app-id`	Defined in the `<id>` field of the CE manifest	Required
`--target-dir`	Specify the directory in which the application is to be created if you prefer not to use the default current working directory	Optional
`--user-app-name`	Specify the name of the application if you prefer to have a name other than the example's default name	Optional

The following example will clone the "MCUBoot Bootloader for PSoC61" application with the desired name "cce-mtb-psoc61-mcuboot-bootloader" configured for the CY8CKIT-062S2-43012 BSP into the specified working directory, C:/mtb_projects:

project-creator-cli --board-id CY8CKIT-062S2-43012 --app-id cce-mtb-psoc61-mcuboot-bootloader --user-app-name cce-mtb-psoc61-mcuboot-bootloader --target-dir "C:/mtb_projects"

Note: The project-creator-cli tool uses the git clone and make getlibs commands to fetch the repository and import the required libraries. For details, see the "Project creator tools" section of the ModusToolbox™ software user guide (locally available at {ModusToolbox™ software install directory}/docs_{version}/mtb_user_guide.pdf).

In third-party IDEs

Use one of the following options:

Use the standalone Project Creator tool:
1. Launch Project Creator from the Windows Start menu or from {ModusToolbox™ software install directory}/tools_{version}/project-creator/project-creator.exe.
2. In the initial Choose Board Support Package screen, select the BSP, and click Next.
3. In the Select Application screen, select the appropriate IDE from the Target IDE drop-down menu.
4. Click Create and follow the instructions printed in the bottom pane to import or open the exported project in the respective IDE.

Use command-line interface (CLI):
1. Follow the instructions from the In command-line interface (CLI) section to create the application, and then import the libraries using the make getlibs command.
2. Export the application to a supported IDE using the make <ide> command.
3. Follow the instructions displayed in the terminal to create or import the application as an IDE project.

For a list of supported IDEs and more details, see the "Exporting to IDEs" section of the ModusToolbox™ software user guide (locally available at {ModusToolbox™ software install directory}/docs_{version}/mtb_user_guide.pdf).

Now this example project has been created for CY8CKIT-062S2-43012 KIT with PSoC62. Customize the BSP for PSoC61 as below.

Notes: While creating/building the project if the following warnings are shown, ignore these warnings. The project will be created/built successfully.

warning: ignoring old recipe for target
warning: overriding recipe for target

Custom BSP for PSoC61

Following section describes how to customize the BSP for PSoC61 in the context of this code example. Please refer to BSP Assistant User Guide for detailed instructions.

Right-click on the project name in ModusToolbox Project Explorer Window and open BSP Assistant by clicking on ModuToolbox > BSP Assistant 1.0) Open the BSP Assistant Tool, and open the BSP that you have created during project creation. Note: When UI version of the BSP assistant is used from the ModusToolbox UI, active BSP will be automatically picked by the BSP Assistant.

Figure 1. Open BSP Assistant 1.0
Change the device to CY8C6136BZI-F34 and Apply changes and close the BSP Assistant.

Note: CY8C6136BZI-F34 is PSoC61 device.

Figure 2. Change the device to PSoC61
Scroll up to Configurators and open Device Configurator. Save the configurations by clicking on File > Save.

This step may generate some error or warning. Close the dialogue box by clicking OK.

Check the Notice List, Two errors will be listed as shown in below figure.

Fix the error corresponding to Error: 'srss[0].clock[0].pathmux[5]' does not exist on the device, by left click on fix and Disable the clock.

Igonre the other errors/warnings regarding Error: There may be an inconsistency between the *.modus file and the makefile target configuration device sets. It will be fixed automatically on next step.
Open the terminal, go to < application > and execute the make eclipse command to Generates launch configs and project files.
```
make eclipse
```

Note: You can use CLI version of the BSP Assistant Tool for the above configurations. Please refer BSP Assistant User Guide

Note: Above steps are to customize an existing BSP for PSoC61. You can also create your own BSP from scratch as described in BSP Assistant User Guide.

Operation

This document expects you to be familiar with MCUboot and its concepts. See MCUboot documentation to learn more.

This example bundles two applications - the bootloader and the blinky app run by CM4. You need to build and program the applications in the following order. Do not start building the applications yet: follow the Step-by-step instructions.

Build and program the bootloader app - On the next reset, CM4 runs the bootloader and prints a message that no valid image has been found.
Build and program the blinky app in BOOT mode (default) - On the next reset, the bootloader will let CM4 run the blinky app from the primary slot. This application toggles the user LED at a 1-second interval.
Build and program the blinky app in UPGRADE mode by setting the make variable IMG_TYPE to UPGRADE - On the next reset, the bootloader will copy this new image from the secondary slot into the primary slot and let CM4 run the image from the primary slot. The application toggles the user LED at a 250-millisecond interval. The user has the option to make the upgrade image permanent in the primary slot or revert to the image that was in the primary slot on reset.

Step-by-step instructions

Connect the board to your PC using the provided USB cable through the KitProg3 USB connector.
Open a terminal program and select the KitProg3 COM port. Set the serial port parameters to 8N1 and 115200 baud.
Install the dependent modules for the imgtool Python module for image signing and key management.

MCUboot already includes this module, but not the dependent modules. Do the following:
1. Open a CLI terminal and navigate to the <mtb_shared>/mcuboot/<tag>/scripts directory.
  
  On Windows, use the command line "modus-shell" program provided in the ModusToolbox™ installation instead of a standard Windows command line application. This shell provides access to all ModusToolbox™ tools. You can access it by typing modus-shell in the search box in the Windows menu.
  
  In Linux and macOS, you can use any terminal application.
2. Run the following command to ensure that the required modules are installed or already present ("Requirement already satisfied:" is printed).
```
python -m pip install -r requirements.txt
```
Build and program the bootloader application.

Using CLI

From the terminal, navigate to _< application >/bootloader and execute the make program_proj command to build and program the application using the default toolchain to the default target. The default toolchain and target are specified in the application's Makefile but you can override those values manually:
```
make program_proj TOOLCHAIN=<toolchain>
```
Example:
```
make program_proj TOOLCHAIN=GCC_ARM
```
After programming, the bootloader starts automatically. Confirm that the UART terminal displays a message as shown follows:

Figure 5. Booting with no bootable image
Build and program the blinky application in the BOOT mode.

Using CLI

From the terminal, navigate to < application >/blinky_app directory and execute the make program_proj command to build and program the application using the default toolchain to the default target.
```
make program_proj TOOLCHAIN=<toolchain>
```
Example:
```
make program_proj TOOLCHAIN=GCC_ARM
```
After programming, the bootloader starts automatically and lets CM4 run the blinky app. Confirm that the user LED toggles at a 1-second interval and the UART terminal displays a message as follows:

Figure 6. Booting with the blinky app in the BOOT mode
Build (Do not program) the blinky application in the UPGRADE mode.
Using Eclipse IDE for ModusToolbox™ software
1. Select the 'blinky' application in the project explorer.
2. Edit the Makefile and update the value of the IMG_TYPE variable to UPGRADE.
3. In the Quick Panel, scroll down, and click Build <Application name>.
Using CLI

From the terminal, navigate to < application >/blinky directory and execute the following command to build the application using the default toolchain to the default target:
```
make build_proj -j8 IMG_TYPE=UPGRADE
```
Program the UPGRADE image using CLI or through Cypress™ Programmer.
Using CLI

From the terminal, navigate to < application >/blinky_app directory and execute the following command to program the UPGRADE image using the default toolchain to the default target:
```
make program_proj -j8 IMG_TYPE=UPGRADE
```
Using Cypress™ Programmer
1. Launch Cypress Programmer and select the probe or kit that you are using.
2. Click on the Open icon and select the UPGRADE image hex file from blinky_app/build/UPGRADE/< BSP-NAME >/<Build Config> directory.
3. If your UPGRADE image is built for an external flash, select and mark the External Memory checkbox.
4. Click Connect and then Program.
After programming, the bootloader starts automatically, upgrades the image by copying the image from the secondary slot into the primary slot, and lets CM4 run the blinky app. Confirm that the UART terminal displays the message as shown follows:

Figure 7. Booting with the blinky app in the UPGRADE mode

Note: The user can build the combined image for bootloader and blinky using the make build CLI command in < application > directory but during the linking stage there might be an error stating multiple definition of symbols for blinky for BOOT and UPGRADE image. Currently the solution to the problem has been addressed in the following code section of the < application >/blinky_app/Makefile which ignores the build artifacts of the other IMG_TYPE. Ex: If BOOT is selected as IMG_TYPE then < application >/blinky/build/UPGRADE/ build directory artifacts will be ignored during the compilation and linking of BOOT image.

ifeq ($(IMG_TYPE), BOOT)
CY_IGNORE+=build/UPGRADE
else
ifeq ($(IMG_TYPE), UPGRADE)
CY_IGNORE+=build/BOOT
endif
endif

For programming the individual builds of bootloader app and blinky app use the make program_proj CLI command as mentioned in the above steps.

Debugging

You can debug the example to step through the code. In the IDE, use the <Application Name> Debug (KitProg3_MiniProg4) configuration in the Quick Panel. For details, see the "Program and debug" section in the Eclipse IDE for ModusToolbox™ software user guide.

Note: (Only while debugging) On the CM4 CPU, some code in main() may execute before the debugger halts at the beginning of main(). This means that some code executes twice – once before the debugger stops execution, and again after the debugger resets the program counter to the beginning of main(). See KBA231071 to learn about this and for the workaround.

Design and implementation

As explained at the beginning of this document, this example bundles two applications - the bootloader app and the blinky app. The blinky app is directly programmed into the flash (internal or external depending on the build parameters) to quickly evaluate the MCUboot operation.

In a real scenario, an application that can download the upgrade image over a wired or wireless communication interface will write the image into the secondary slot. For example, mtb-example-ota-mqtt is implemented using the ota middleware.

The MCUboot repo in GitHub also includes two apps - MCUbootApp and BlinkyApp - for PSoC™ 62 MCU devices. The functionality of this code example is the same as those apps. In this example, the bootloader app reuses a lot of source files (see bootloader/app.mk for the exact list of files) from MCUbootApp.

This code example uses ModusToolbox™ software resources such as BSPs and PSoC™ 6 MCU to provide a rich development experience that aligns well with other code examples based on ModusToolbox™ software.

Design and implementations are similar to that of [mtb-example-psoc6-mcuboot-basic] (https://github.com/Infineon/mtb-example-psoc6-mcuboot-basic) example; execpt both Bootloader and Applications are designed to run from CM4 CPU and tested on only PSoC61 device.

There are three types of swap modes supported in MCUboot - scratch, move, and using a status partition. Only swap mode using status partition can be used with PSoC™ 6 MCU devices because of the hardware restriction of the large minimum flash write/erase size. The MCUboot library is designed with the minimum flash to write/erase size to be 8 bytes or less. This is to ensure that data is not lost when writing to the flash sector status so that it is a single-cycle operation ensuring the robustness of the application.

Because PSoC™ 6 MCU devices have a large minimum flash write/erase size, swap using status partition has been implemented. Using this algorithm, a separate area in the internal flash is used to store swap status values and the image trailer data such as the swap size and info, boot image magic value, and the image ok field.

MCUboot is a library that helps to implement secured bootloader applications for 32-bit MCUs.

See the "Swap status partition description" section of the MCUbootApp documentation.

See MCUboot design documentation for details.

Resources and settings

Table 1. Application resources

Resource	Alias/object	Purpose
UART (HAL)	cy_retarget_io_uart_obj	UART HAL object used by Retarget-IO for Debug UART port
UART (HAL)	uart_modem_obj	UART HAL object used for communicating with LTE Modem
GPIO (HAL)	UART_MODEM_RESET	User GPIO used to reset LTE Modem
GPIO (HAL)	CYBSP_USER_LED	User LED controlled by the subscriber based on incoming MQTT messages
GPIO (HAL)	CYBSP_USER_BTN	User button used to notify the publisher to publish MQTT messages

Customizing and selecting the flash map

A flash map for example is selected by changing the value of the FLASH_MAP variable in the <application>/user_config.mk file to the desired JSON file name. Supporting only psoc6_swap_single.json and psoc6_overwrite_single.json JSON files.

See How to modify flash map section to understand how to customize the flash map to your needs.

Before the pre-build stage, the flashmap JSON file is automatically parsed by the <application>/scripts/memorymap_<family>.py python script to generate the following files:

memorymap.mk, memorymap.c and memorymap.h files in the bootloader example.
memorymap.mk, memorymap.c and memorymap.h files in the blinky example.

The parameters generated in the memorymap.mk file are used in the DEFINES and LDFLAGS variables of the application Makefile.

The structures generated in the memorymap.c and memorymap.h files are used by the cy_flashmap.c file in the MCUboot library.

Note: While modifying the flash map, make sure the primary slot, secondary slot, and bootloader application flash sizes are appropriate. In this code example, it will automatically match the application linker scripts flash memory allocation with the memorymap.c and user_config.mk files.

Configuring make variables

This section explains the important make variables that affect the MCUboot functionality. Some of these variables are autogenerated from the flashmap JSON file and some variables can be updated directly in the Makefile or passed along with the make build command.

Common make variables

These variables are common to both the bootloader and blinky apps and are configured via the <application>/user_config.mk file.

Variable	Default value	Description
`SIGN_KEY_FILE`	cypress-test-ec-p256	Name of the private and public key files (the same name is used for both keys)
`BOOTLOADER_SIZE`	Autogenerated	Flash size of the bootloader app run by CM0+. In the linker script for the bootloader app (CM0+), the `LENGTH` of the `flash` region is set to this value. In the linker script for the blinky app (CM4), the `ORIGIN` of the `flash` region is offset to this value.
`BOOTLOADER_APP_RAM_SIZE`	0x20000	RAM size of the bootloader app run by CM0+. In the linker script for the bootloader app (CM0+), `LENGTH` of the `ram` region is set to this value. In the linker script for the blinky app (CM4), the `ORIGIN` of the `ram` region is offset to this value, and the `LENGTH` of the `ram` region is calculated based on this value.
`SLOT_SIZE`	Autogenerated	Size of the primary slot and secondary slot. i.e., flash size of the blinky app run by CM4.
`MCUBOOT_HEADER_SIZE`	0x400	Size of the MCUboot header. Must be a multiple of 1024 (see the following note). Used in the following places: 1. In the linker script for the blinky app (CM4), the starting address of the`.text` section is offset by the MCUboot header size from the `ORIGIN` of the `flash` region. This is to leave space for the header that will be later inserted by the imgtool during post-build steps. 2. Passed to the imgtool while signing the image. The imgtool fills the space of this size with zeroes (or 0xFF depending on internal or external flash) and then adds the actual header from the beginning of the image.
`MAX_IMG_SECTORS`	Autogenerated	Maximum number of flash sectors (or rows) per image slot for which swap status is tracked in the image trailer.
`MCUBOOT_IMAGE_NUMBER`	Autogenerated	The number of images supported in the case of multi-image bootloading.
`PRIMARY_IMG_START`	Autogenerated	Starting address of primary slot.
`SECONDARY_IMG_START`	Autogenerated	Starting address of secondary slot.

Note: The value of MCUBOOT_HEADER_SIZE must be a multiple of 1024 because the CM4 image begins immediately after the MCUboot header and it begins with the interrupt vector table. For PSoC™ 6 MCU, the starting address of the interrupt vector table must be 1024-bytes aligned.

Number of bytes to be aligned to = Number of interrupt vectors x 4 bytes

i.e., 1024 = 256 vectors x 4 bytes (32-bit address) per vector.

PSoC™ 6 MCU supports up to 240 external interrupts in addition to the 16 system exceptions provided by CM4. See the description of the CPUSS_CM4_VECTOR_TABLE_BASE register in PSoC™ 6 registers technical reference manual and the description of the vector table offset register (VTOR) in Cortex®-M4 (ARMv7-M) architecture technical reference manual for details.

Bootloader app make variables

These variables are configured via bootloader_app/Makefile.

Variable	Default value	Description
`USE_OVERWRITE`	Autogenerated	Value is 1 when scratch and status partitions are not defined in the flashmap JSON file.
`USE_EXTERNAL_FLASH`	Autogenerated	Value is 1 when external flash is used for either primary or secondary slot.
`USE_XIP`	Autogenerated	Value is 1 when primary image is placed on external memory.

Blinky app make variables

These variables are configured via blinky_app/Makefile.

Variable	Default value	Description
`IMG_TYPE`	BOOT	Valid values: BOOT, UPGRADE BOOT: Use when the image is built for the primary slot. The `--pad` argument is not passed to the imgtool. UPGRADE: Use when the image is built for the secondary slot. The `--pad` argument is passed to the imgtool. Also, the blinky app defines the LED toggle delay differently depending on whether the image is BOOT type or UPGRADE type.
`HEADER_OFFSET`	Auto-calculated	The starting address of the CM4 app or the offset at which the header of an image will begin. Value equal to (`SECONDARY_IMG_START` - `PRIMARY_IMG_START`).
`USE_OVERWRITE`	Autogenerated	Value is 1 when scratch and status partitions are not defined in the flashmap JSON file.
`USE_EXTERNAL_FLASH`	Autogenerated	Value is 1 when an external flash is used for either primary or secondary slot.
`USE_XIP`	Autogenerated	Value is 1 when the primary image is placed on external memory.
`KEY_FILE_PATH`	../<application>/keys	Path to the private key file. Used with the imgtool for signing the image.
`APP_VERSION_MAJOR` `APP_VERSION_MINOR` `APP_VERSION_BUILD`	1.0.0 if `IMG_TYPE=BOOT` 2.0.0 if `IMG_TYPE=UPGRADE`	Passed to the imgtool with the `-v` option in MAJOR.MINOR.BUILD format, while signing the image. Also available as macros to the application with the same names.

Usage of external flash

This section provides a quick overview of external flash support with MCUboot for PSoC™ 6 MCU. External flash support refers to placing the primary/secondary/both slots into an external flash. This helps to increase the available internal flash for the primary slot or to support update operation on MCUs with lower internal flash size.

MCUboot accesses the external NOR flash using the serial memory interface (SMIF) aka 'QSPI peripheral block' in PSoC™ 6 MCU. The SMIF block supports interfacing with QSPI devices; most of the PSoC™ 6 MCU development kits include a QSPI NOR flash. For example, the CY8CPROTO-062-4343W kit includes the S25FL512S, which is a 64-MB (512-Mbit) QSPI NOR flash. MCUboot for PSoC™ 6 MCU uses the serial flash discoverable parameter (SFDP) standard to auto-discover the flash read/write commands and other parameters. Ensure that the NOR flash on your board supports this standard. See ExternalMemory.md for more information on working with the external flash.

During post-build steps, the image address is relocated to begin from the external flash address using the following command:

arm-none-eabi-objcopy --change-addresses=HEADER_OFFSET -O ihex <input.elf> <output.hex>

Note: If you are placing more than one image in the external flash, ensure that the starting address of the images is aligned to the erase sector size of the NOR flash. For S25FL512S, the erase sector size is 256 KB (0x40000).

External flash programming

The programmer tool for PSoC™ 6 MCU (based on OpenOCD) programs the external flash with the data from the HEX file when the address of the data is 0x18000000 or higher. The programmer tool requires the configuration information (e.g., erase/read/program commands) about the external flash present on the board to be able to program the flash. This configuration is placed into the user area of the internal flash, and the address pointing to the configuration is placed into the TOC2 section of the supervisory flash (SFlash) area of the internal flash. The programmer tool understands the TOC2 structure and knows where to look for the address that points to the external flash configuration. See PSoC™ 6 MCU programming specifications for more information on SFlash and TOC2.

The mtb_shared/mcuboot/<tag>/boot/cypress/MCUBootApp/cy_serial_flash_prog.c file defines the TOC2 structure and the cycfg_qspi_memslot.c./h files under bsps/TARGET_< BSP-NAME >/config/GeneratedSource hold the external flash configuration structures. These files are autogenerated from design.cyqspi under bsps/TARGET_< BSP-NAME >/config using the QSPI configurator tool.

Note: Initially the customized configuration files like - design.cyqspi, design.cycapsense, design.modus are present in the folder templates/TARGET_< BSP-NAME >/config and are copied automatically from this folder to bsps/TARGET_< BSP-NAME >/config during the library updates. The build system reads all these configurations from the bsps/TARGET_< BSP-NAME >/config.

Note: Although the bootloader app uses SFDP to autodiscover the external flash configuration, a static configuration must be present in the internal flash for programming to work. It is possible to program without storing the configuration in the internal flash. However, in that case, external memory programming is limited only to the PSoC™ 6 MCU + NOR flash device combinations that are on the PSoC™ 6 MCU development kits.

Security

Note: This example simply demonstrates the image-signing feature of MCUboot. It does not implement root of trust (RoT)-based secured services such as secured boot and secured storage (to securely store and retrieve the keys). You must ensure that adequate security measures are implemented in your end product. See the PSoC™ 64 line of secured MCUs that offer those advanced security built-in features, and read this whitepaper that compares the security features between PSoC™ 64 'secure' MCU and PSoC™ 62/63 MCUs.

MCUboot checks the image integrity with SHA256, and image authenticity with digital signature verification. Multiple signature algorithms are supported; this example enables ECDSA SECP256R1 (EC256) by default. MCUboot uses the Mbed TLS library for cryptography.

PSoC™ 6 MCU supports hardware-accelerated cryptography based on the Mbed TLS library via a shim layer. The cy-mbedtls-acceleration library implements this layer. Hardware-accelerated cryptography shortens the boot time by more than four times compared to the software implementation (observation results).

Note: In the current version of the MCUBoot library (v1.8.1-cypress), hardware crypto acceleration is not supported.

MCUboot verifies the signature of the image in the primary slot every time before booting when MCUBOOT_VALIDATE_PRIMARY_SLOT is defined. In addition, it verifies the signature of the image in the secondary slot before copying it to the primary slot.

This example enables image authentication by uncommenting the following lines in the bootloader/libs/mcuboot/boot/cypress/MCUbootApp/config/mcuboot_config/mcuboot_config.h file:

#define MCUBOOT_SIGN_EC256
#define NUM_ECC_BYTES (256 / 8)
.
.
.
#define MCUBOOT_VALIDATE_PRIMARY_SLOT

When these options are enabled, the public key is embedded within the bootloader app. The blinky app is signed using the private key during the post-build steps. The imgtool Python module included in the MCUboot repository is used for signing the image.

This example includes a sample key pair under the <application>/keys directory. You must not use this key pair in your end product. See Generating a key pair for generating a new key pair.

Generating a key pair

You can use the imgtool Python module to generate the keys.

Generate the private key:

python imgtool.py keygen -k priv_key.pem -t ecdsa-p256

Extract the public key in the form of a C array:

python imgtool.py getpub -k priv_key.pem >> pub_key.pub

Pre- and post-build steps

Bootloader app: Pre-build steps

The pre-build steps are specified through the PREBUILD variable in bootloader_app/Makefile.

Initialize the Git submodules for MCUboot: This is required because the library manager updates currently does not support initializing Git submodules while cloning a repo. This step executes only if the libs/mcuboot/ext/mbedtls directory (a submodule) does not exist or if the content of the directory is empty.
Generate the external flash configuration files: This step generates the cycfg_qspi_memslot.c./h files under the bsps/TARGET_< BSP-NAME >/config/GeneratedSource directory. This step is required because QSPI is not enabled in design.modus. This is done to avoid initializing the QSPI block in the generated source because it is initialized in the SFDP mode by the bootloader app in main.c. psoc6make autogenerates the source files from the configurator tools only if the peripheral is enabled in design.modus.

Blinky app: Post-build steps

The post-build steps are specified through the POSTBUILD variable in blinky_app/Makefile. These steps generate the signed version of the image in HEX format using the imgtool Python module. The SIGN_ARGS variable holds the arguments passed to the imgtool. The final image is in HEX format so that PSoC™ 6 MCU programmer tools can directly program the image into the device. If you are generating the image to use with a firmware update application running on the device, you may need to convert the image into binary (BIN) format.

Make a copy of the *.hex file into a *_raw.hex file.
Delete the *.hex file because the final signed image will be generated with the same filename so that you can directly program the file either using the make program_proj command or using the launch configurations in the Eclipse IDE for ModusToolbox™ software.
Relocate the address and generate a new *_unsigned.hex file from the *.elf file using the arm-none-eabi-objcopy tool.
Sign the image using imgtool and generate the *.hex file.

Bootloader app: Custom device configuration

Initially the customized configuration files like - design.cyqspi, design.cycapsense, design.modus are present in the folder templates/TARGET_< BSP-NAME >/config and are copied automatically from this folder to bsps/TARGET_< BSP-NAME >/config during the library updates. The build system reads all these configurations from the bsps/TARGET_< BSP-NAME >/config. The custom configuration just enables the serial communication block (SCB) in the UART mode with the alias CYBSP_UART. libs/mcuboot/boot/cypress/MCUbootApp/cy_retarget_io_pdl.c uses this block to implement redirecting printf to UART.

Design notes

Both the bootloader app and the blinky app implement redirecting printf to the serial port (UART). Both apps use the same SCB (UART) block to communicate with the USB-to-UART bridge provided by KitProg3. The bootloader app runs first, initializes the UART block, prints the messages, and then boots the blinky app which then again initializes the same UART block and prints messages. There is no conflict currently because the apps do not print simultaneously.
HAL drivers do not support CM0+. All codes written for the bootloader app use the PDL drivers only.
Bootloader app does not initialize the system clocks and resources; call init_cycfg_system() to let CM4 initialize them.

Resources and settings

Table 1. Bootloader app

Resource	Alias/object	Purpose
SCB UART (PDL)	CYBSP_UART	Used for redirecting printf to UART port.
SMIF (PDL)	QSPIPort	Used for interfacing with QSPI NOR flash.

Table 2. Blinky app

Resource	Alias/object	Purpose
UART (HAL)	cy_retarget_io_uart_obj	UART HAL object used by retarget-IO for debug UART port
GPIO (HAL)	CYBSP_USER_LED	User LED

Related resources

Resources	Links
Application notes	AN228571 – Getting started with PSoC™ 6 MCU on ModusToolbox™ software AN215656 – PSoC™ 6 MCU: Dual-CPU system design
Code examples	Using ModusToolbox™ software on GitHub Using PSoC™ Creator
Device documentation	PSoC™ 6 MCU datasheets PSoC™ 6 technical reference manuals
Development kits	Select your kits from the Evaluation board finder page
Libraries on GitHub	mtb-pdl-cat1 – PSoC™ 6 peripheral driver library (PDL) mtb-hal-cat1 – Hardware abstraction layer (HAL) library retarget-io – Utility library to retarget STDIO messages to a UART port
Middleware on GitHub	MCUboot – Open-source library enabling the development of secure bootloader applications for 32-bit MCUs capsense – CAPSENSE™ library and documents psoc6-middleware – Links to all PSoC™ 6 MCU middleware
Tools	Eclipse IDE for ModusToolbox™ software – ModusToolbox™ software is a collection of easy-to-use software and tools enabling rapid development with Infineon MCUs, covering applications from embedded sense and control to wireless and cloud-connected systems using AIROC™ Wi-Fi and Bluetooth® connectivity devices. PSoC™ Creator – IDE for PSoC™ and FM0+ MCU development

Other resources

Infineon provides a wealth of data at www.infineon.com to help you select the right device, and quickly and effectively integrate it into your design.

For PSoC™ 6 MCU devices, see How to design with PSoC™ 6 MCU - KBA223067 in the Infineon community.

Document history

Document title: CCE236897 - MCUboot based Basic Bootloader for PSoC 61

Version	Description of change
1.0.0	New code example
1.0.1	Custom BSP for PSoC61: Updates on README
1.0.2	Minor README Updates
1.0.3	Changes in deps folder
2.0.0	Included support for mcubootv1.9.1

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cce-mtb-psoc61-mcuboot-bootloader/README.md

MCUboot based Basic Bootloader for PSoC 61

Requirements

Supported toolchains (make variable 'TOOLCHAIN')

Supported Kit

Software setup

Using the code example

Custom BSP for PSoC61

Operation

Step-by-step instructions

Debugging

Design and implementation

Resources and settings

Customizing and selecting the flash map

Configuring make variables

Common make variables

Bootloader app make variables

Blinky app make variables

Usage of external flash

External flash programming

Security

Generating a key pair

Pre- and post-build steps

Bootloader app: Pre-build steps

Blinky app: Post-build steps

Bootloader app: Custom device configuration

Design notes

Resources and settings

Related resources

Other resources

Document history