Using the Library to jump from the User Code to the Bootloader Code in the HT66FB5x0 and HT68FB5x0

Transcription

1 Using the Library to jump from the User Code to the Bootloader Code in the HT66FB5x0 and HT68FB5x0 D/N : AN0322E Introduction Holtek s USB Flash MCU series devices, the HT66FB5x0 and HT68FB5x0, include a Bootloader function. The devices can jump from the user s code to the Bootloader Code to implement a Flash Program Memory update. This application note uses the HT66FB550 to describe how to implement this function using the Library. Operating Principles The HT66FB5x0 and HT68FB5x0 series devices include a Bootloader function which can be used to implement Flash Program Memory updates using the ISP. When the user code is running, if there is a call to the subroutine provided by the library file to enable the Bootloader, then after a reset or power-on reset, the MCU will begin to execute the Bootloader Code. At this point the MCU downloads the new program from the PC via the USB interface to update the Flash Program Memory. By using the appropriate settings, the MCU can then restart and run the new program. In the HT-IDE3000 Program setting, select with Bootloader. After compiling, an MTP file will be generated. Then program the Bootloader Code and the current user program into the IC using the latest version of the HOPE3000. The user can choose to use the ISP provided by the Holtek IDE or a self-developed IAP program. If the ISP provided by Holtek IDE is chosen, it will take 0.5K words of Flash Program Memory space. The HT66FB550 Flash size is 8K 16 bits, which after deducting the ISP space, leaves 7.5K 16 bits available for user developed programs. The structure is shown below: 1

2 To jump to the Bootloader Code, users have to add a library file Enable_BootLoader v1.3.lib to their project. When the condition that jump to the Bootloader in the program is met, call the subroutine provided by the library file to determine the success of the enable Bootloader Mode action. If it is successful, reset the MCU by an external reset, restart or intentionally allow the WDT to overflow to execute the Bootloader Code. When the MCU is connected to the PC via the USB interface, and the USB enumeration is successful, users can then use the I3000.exe provided by Holtek or use a self-developed AP to communicate with the Bootloader Code and transfer the new program, to complete the user program update. The specific steps are as follows: 1. Create a project, check with Bootloader in the Project Settings and select Start at User mode. Add the library file Enable_BootLoader v1.3.lib in the Linker Options Libraries. The library file can be obtained as shown in the attached program. 2. Write, compile the program and call the subroutine ENABLE_BL provided by the library file at the place where it is required to jump to the bootloader code. In the library file Enable_BootLoader v1.3.lib there are four byte variables (temp1~temp4) and one bit flag (B_ENABLE_BL_OK) which must be declared as Extern in the User code. The flag B_ENABLE_BL_OK is used to indicate the success or failure to enable the Bootloader Mode. A value of 1 indicates success, 0 indicates failure. 3. Using the latest version of the HOPE3000, program the project s MTP file into the HT66FB550 using the e-writerpro programmer. 4. Along with the peripheral circuit, including the USB interface, the HT66FB550 will operate normally after power on. When the pre-set conditions are met, such as having some keys pressed at the same time, the Bootloader mode will be enabled. After a restart or reset operation, the MCU will jump from user code to the Bootloader Code. 5. Run the I3000.exe program on the PC. The HT66FB550 is connected to PC via the USB interface and powered via the USB. When the USB is connected, the Download Mode is selected and displayed on the I3000.exe interface, indicating that the HT66FB550 USB interface has been connected successfully and that the 2

3 new program s MTP file can be programed into the HT66FB550 using the I3000.exe program without the programmer. 6. Program new program s MTP file. In the I3000.exe, open the new program s MTP file. Click Erase button on the right side of the I3000.exe interface, select Select All, press OK button erase all. Then click the Program button to program to the MCU. Click the Verify button to verify whether the code has been programmed to the IC successfully. 7. Select the MCU start mode. Click the MCU Start button and a dialogue box as follows will appear. Select the MCU starts at the user firmware, then click OK. 8. After select the start mode, a process bar appears as follows Execute Program, some time later, the I3000.exe prompts the machine needs to be rebooted!. At this point, disconnect the USB connection and re-power the MCU. Now the HT66FB550 will start to execute the updated program based on the selected mode. 3

4 Application Circuit The application circuit includes a USB communication interface, a reset circuit, LED 8 circuit, single key circuit and the HT66FB550 etc. The USB interface circuit provides the power supply for the entire application circuit and communicates with the USB host. The resistors and capacitors connected to the USB signal line D+ D- are primarily used to match the impedance of the signal line, which can reduce interference and improve the communication reliability as well as reduce the probability of Data Errors during transmission. Using a Ferrite Bead, the USB host can provide a stable power supply for the application circuit. However, if the device is being programmed using by the e-writerpro, the USB cable should be removed. The program example user code before being updated is used to implement an 8 LED incrementing light function. Each pin on the PC port is used as an output to control an LED. PB6 is set as input to detect whether a key is pressed. If the valid key pressed status is detected, the Bootloader Mode is enabled. After the MCU restarts or wait for the WDT to overflow, the MCU will be reset and the system will jump to the Bootloader Code. At this point, using the I3000.exe, download the new program and update the Flash Program Memory. The updated program implements an 8 LED cyclic shift light function. To obtain the specific program code, refer to the attached files. Finally select the MCU Start mode and the MCU will restart to execute the new program. 4

5 S/W Flowchart Program Description After power on, firstly the program starts with a system initialisation, including clearing the USBCKEN bit, disabling the USB clock, clearing RAM Bank0, enabling the WDT and configuring the PC port as an output to drive 8 LEDs. PB6 is used as an input to enable the action that jumps to the Bootloader Code. When the initialisation has finished, the device begins to execute the user code, to implement the PC0~PC7 LEDs illumination pattern. The system examines if the PB6 input is low at intervals of about 340 s. If it detects continuous 25 low levels, which means the low status exists for about 8.5ms, the key press action is taken as effective, to which it then implements the enable Bootloader action. Call the subroutine ENABLE_BL in the Enable_BootLoader v1.3.lib library file to detect whether the flag B_ENABLE_BL_OK is 1 to determine whether the enable action is successful. If successful, the program enters a loop. Then the MCU will power up again or wait for the WDT to overflow to reset the MCU. The system has then moved from the user code to the Bootloader Code. After entering the Bootloader Code, the MCU, via the I3000.exe, downloads the new program which can implement a PC0~PC7 LEDs cyclic shift light. The system also needs to determine whether the key is pressed at of about 340 s to enable the Bootloader. Then select the program to start from the User Mode. After re-powering on, the MCU begins to execute the User Code to achieve the 8 LEDs cyclic shift operation. 5

6 Program Example configuration option: High Freq.OSC: Low Freq.OSC: LIRC Fsub clock source: ;other option select by user. HIRC LIRC The subroutine, variables and flag of the calling library file are declared as follows in the program extern ENABLE_BL : near extern B_ENABLE_BL_OK : bit extern temp1 : byte extern temp2 : byte extern temp3 : byte extern temp4 : byte Program code and description: refer to the attached files Conclusions Using the HT66FB550 device, this application has described how to implement the jump from the user code to the Bootloader Code using the Library. In the Bootloader Code, it was also shown how new programs can be downloaded using the I3000.exe and how to make related settings and execute programs in the User Mode. Attachments Source Code file: HT66FB550_EFromBL_1.rar Source Code file for update: HT66FB550_EFromBL_2.rar 6