AN4759
STM32L4 API and tamper detection application example
3STM32L4 API and tamper detection application example
3.1STM32CubeL4 firmware libraries for tamper detection
The RTC comes with:
•a firmware driver API abstracting the RTC features for the end user
Refer to stm32l4xx_hal_rtc.c and stm32l4xx_hal_rtc_ex.c files in \STM32Cube_FW_L4_Vx.y.z\Drivers\STM32L4xx_HAL_Driver\
•a set of example projects in \STM32Cube_FW_L4_Vx.y.z\Projects\STM32L476RG-Eval\Examples\RTC
3.2X-CUBE-RTC for tamper detection
X-CUBE-RTC shows an example where a real-time clock must be maintained alive while using as low power
as possible (STM32CubeExpansion_AN4759_RTC_STM32L_Vx.y.z\Projects\STM32L476G_EVAL\RTC_ TamperVBATT).
The firmware implements:
•a few hints in order to ensure a low current consumption
•a display in the debugger (date and time, timestamp date and time) and on LEDs (power-up events, reset events, tamper events, error)
•a display on the TFT screen, using STemWin library
•tampering detection capability, both when the main power supply (VDD) is present and when the RTC is battery powered
•ability to timestamp the tampering event
•ability to erase the backup registers that may contain sensitive data upon tamper detection
AN4759 - Rev 8 |
page 35/60 |
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AN4759
X-CUBE-RTC for tamper detection
The application flowchart is shown in the figure below.
Figure 18. Application example flowchart
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Initialization |
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Configure RTC |
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Tamper interrupt |
clock and |
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handler |
prescalers |
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Green LED on |
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Tamper |
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Green LED on |
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(LED1) |
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detection during |
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Yes |
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(LED1) |
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power-down ? |
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No
Rise flag for main
program
Configure tamper detection on PA0
Return to main program
Always executed (upon system reset)
Executed upon power-on reset
Executed upon back-up domain reset
Backup |
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Write backup |
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registers |
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Yes |
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register |
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erased? |
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No |
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Power-oN |
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Red LED on |
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reset |
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Yes |
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(LED2) |
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occurred ? |
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No
End of initialization
Display date and time
Power-oN reset occurred ?
Yes
Configure
calendar
No
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Enter low-power |
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No |
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Display timestamp date and time |
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mode (Stop 2) |
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Check backup registers are cleared |
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Tamper |
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detected in IT |
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Yes |
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Deactivate tamper |
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? |
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AN4759 - Rev 8 |
page 36/60 |
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