Porting Paulus on NXP Kinetis K2x

File structure

After installation of Paulus the source code is stored in the file structure shown in Table 1 describes the contents.

Table 1: File structure

The initialization of the CAN controller is done in module k2x / k2x_can.c.

In module k2x / k2x_init.c the I/O pins for the CAN interface have to be initialized.

In module k2x / k2x_init.c there must be the functions getBitRate() and getNodeId() available. Usually the CANopen network parameters are provided by reading jumpers or by loading from flash memory.

Development environment

Paulus on the platform of Freescale Kinetis K2x was developed with the Kinetis Design Studio v2.0.0 and alternatively IAR Workbench for ARM v8.50.9. As Hardware environment Freescale evaluation board TWR-K20D72M with a K20DX256x as target CPU.

Paulus configuration

In general the initialization function initializes only the absolutely necessary peripherals like clock system, CAN controller, memory management as needed by Paulus and a timer for Heartbeat or LSS. Nevertheless, there might be situations where it makes sense that Paulus initializes other functionalities which are later used by the application as well. As an example consider the serial interface for debug messages.

CAN bit rate

The CAN bit rate is coded by the index of the CAN bit timing table according to /CiA-305/. The index of the default CAN bit rate is specified about the compiler-define BITRATE_INDEX_<bit_rate> in /k2x/bl_config.h:

#define BL_USED_BITRATE_INDEX   BITRATE_INDEX_125K

The default CAN bit rate is 125 kbit/s and can be changed by LSS services. The LSS services are described in /Paulus_man/ and base on /CiA-305/. The supported CAN bit rates are depending on the clock of the CAN controller and are listed in / k2x/ k2x_can.c. The value FFh for segment3 marks unsupported CAN bit rates. The clock for the activation of the CAN bit rate is generated by timer Systick with a period of 1 ms.

Heartbeat producer

Timer Systick is also used for the generation of Heartbeat producer messages.

Debug output

By the compiler-define DEBUG a debug output can be activated about the serial interface UART1. The compiler-define is set in file / k2x /bl_config.h:

#define DEBUG 1

In general the initialization function will initialize only the absolutely necessary peripherals like clock system, CAN controller, memory management as needed by Paulus. Nevertheless, there might be situations where it makes sense that Paulus initializes other functionalities which are later used by the application as well. As an example consider the serial interface for debug messages.

Generating application software

The application software consists of an application header and an application program.

Open

The application program has to be prepared for download by the following steps:

•     build the application program in binary format

•     calculate the CRC of the application program, build the application header and generate the application software to download

•     configure the start address of the application software in Paulus

Paulus checksum

The program paulus_cksum calculates the CRC checksum of the binary application program generates the application header and stores the application header and the application program in a new file. This file can be loaded in the device by Paulus.

Unused bytes in the application header are set to 0x00 with the K2x. The length of the application header is 256 bytes.

Example: The download file for the application program s1_download.bin is generated about Windows console:

Besides checking the CRC Paulus checks also the size of the application header. A size of 0 is invalid. An application may destroy the ’valid’ information by overwriting the size with 0. That is always possible on the K2x FLASH, because the byte content is 0xFF after erasing.

More detailed information from this tool can find in /Paulus_CRC/.

To prepare: In order to produce a usable binary file from the Intel hex file output of the IDE you can use the free software tool HEX2BIN.

See example in Windows console:

Start address

It is important that the start address of the application software in the flash memory and the information in the Paulus configuration in k2x/k2x_flash.h are identical. The application software is stored as a separate program in the flash memory additionally to the bootloader program. Therefore the application software is flashed to:

#define FLASH_PROGRAM_START_ADR   0x00008000

The length of the application header is 256 byte. The program start of the application is at address (FLASH_PROGRAM_START_ADR + 256 bytes).

Memory

Shared RAM

The shared RAM for data exchange between bootloader and application starts at address 0x20000000. The size of the shared RAM is specified in k2x/bl_interface.h by the compiler-define BL_JUMPCODE_SIZE. The shared memory is installed in k2x/bl_interface.h as follow:

The keyword for the re-start of the application program is set in byte 0-3 of jumpcode. Paulus uses the keyword “APPL” or “BOOT”  to start the application program, see /Paulus_man/.

Flash

The total size of the K20DX256x flash is 256Kb. The current implementation of Paulus occupies a memory area of 32Kb from this. Therefore 224 Kb (less 0x100 byte crc header) flash memory area available for the application software.

The flash area for configuration data of Paulus is located at address 0x00000800. On this address and the following Paulus stores the node-ID and the CAN bit rate index during the execution of the LSS service “LSS store configuration“. The addresses are configurable in k2x/bl_interface.h:

After the next re-start Paulus uses this node-ID and this CAN bit rate index for communication. The new CAN bit rate cannot be activated by NMT-Command Reset Application. If the LSS services are not used, Paulus uses the node-ID and CAN bit rate index configured in k2x/bl_config.h.

Example application

CANopenSlave1 is an example for an application program. The directory example/ CANopenSlave1 contain the compiler project and the application-specific functions. For compilation the CANopen Library and the suitable driver package is necessary. The CANopen Library and the driver package belong not to the delivery scope of Paulus. The example serves as a template for your own application. The binary application software in example/ CANopenSlave1/bin/s1_download.bin can be used for a quick start.

The linker file of this example project is adapted on these memory requirements (flash addresses and shared RAM section).

See settings in linker file (..\examples\CANopenSlave1_K2x\examples\s1MK20DX256xxx10_flash.ld):

This example has included source files bl_interface.c, bl_interface.h from bootloader. The application program can request an update by jumping back into Paulus by writing of the program control command start application program (value 1) on object 1F51h/1. The application program calls the macro BOOTLOADER_JUMP(APPL). This call is implemented in usr_301.c /sdoWrInd(). The application program stores the keyword “APPL” in the shared RAM and jumps into Paulus. Paulus is re-started and stays running until the application program is started by command.

If the example application program is running the CANopen slave starts with his bootup followed by heartbeat messages over the CAN-bus.

References

Table 2: References