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Why STM32F100RBT6B is Not Starting After Power On

Troubleshooting: Why STM32F100RBT6B Is Not Starting After Power On

Possible Causes for the Issue

When an STM32F100RBT6B microcontroller fails to start after power on, the issue can be caused by several factors, including hardware or software-related problems. Here are some common reasons:

Power Supply Issues: Inadequate Voltage: If the power supply voltage is insufficient or unstable, the microcontroller may fail to boot. The STM32F100RBT6B typically requires 2.0V to 3.6V. Power Ripple: A noisy power supply with voltage ripples can cause unreliable operation or prevent the MCU from starting. Clock Configuration Problems: Incorrect Clock Source: The microcontroller may fail to initialize if the clock source is not correctly configured. The STM32F100RBT6B uses an internal or external clock source (HSE or HSI). A failure to select or configure the correct clock source can prevent the MCU from starting. Watchdog Timer Timeout: The Watchdog Timer (WDT) might be enabled and not reset by software during startup. If the WDT is not cleared within the expected timeframe, it can cause the MCU to reset continuously, making it appear as though it’s not starting. Boot Configuration Pins: The STM32F100RBT6B has specific boot configuration options controlled by the BOOT0 and BOOT1 pins. If these pins are not correctly configured, the MCU may fail to boot from Flash Memory . Faulty Firmware or Incorrect Startup Code: If the firmware is corrupted or incorrectly configured, the MCU might not reach its main application code and therefore will not start as expected. Reset Pin Issues: If the reset pin (NRST) is not properly handled, either due to noise, faulty connection, or improper pull-up/pull-down configuration, the MCU might stay in a reset state or fail to reset correctly. External Peripheral Interference: External components, such as sensors, actuators, or communication module s, may cause interference with the MCU’s operation. Ensure that there is no short-circuit or misconfigured peripheral that could prevent the MCU from starting. Step-by-Step Troubleshooting and Solutions Verify Power Supply: Check Voltage Levels: Ensure that the power supply provides a stable voltage between 2.0V and 3.6V (check datasheet for exact values). Measure Ripple: Use an oscilloscope to check for excessive noise or voltage fluctuations on the power supply line. A clean and stable voltage is crucial. Check Clock Source Configuration: Internal vs. External Clock: Verify if the microcontroller is configured to use the correct clock source (HSI for internal or HSE for external). If using HSE, ensure that the external crystal or oscillator is connected and functional. Use Debugging Tools: If unsure, use a debugger or serial interface to check the clock source selection and correct any issues. Inspect Watchdog Timer (WDT): Disable WDT (for Testing): Temporarily disable the Watchdog Timer in the code to see if the MCU starts properly. If the MCU works after disabling the WDT, check that the software properly resets the WDT during startup. Configure WDT Correctly: If WDT is necessary for your application, ensure it is being handled correctly in the code, with appropriate timeout settings. Verify Boot Configuration Pins (BOOT0 and BOOT1): Check Pin Status: The BOOT0 and BOOT1 pins should be configured according to your desired boot mode (from Flash, System Memory, or SRAM). Typically, BOOT0 should be low (0) for booting from Flash memory, while BOOT1 should be low (0) for normal boot operation. Correct Pin Settings: Make sure that the pins are not floating or incorrectly pulled up/down. Examine Firmware and Startup Code: Check Firmware Integrity: Ensure the firmware is correctly programmed into the Flash memory. You can try re-flashing the MCU with known-good firmware to rule out corrupted code. Debug the Startup Code: If using a debugger, step through the startup code (from the reset vector) to confirm the MCU is correctly initializing its system. Verify Reset Pin (NRST): Check for Proper Reset Handling: Ensure that the NRST pin is connected properly to the reset circuitry. If there is a weak or noisy reset signal, the MCU may fail to start. Check for External Reset Sources: If using external reset ICs, verify that they are functioning correctly. Check for External Peripheral Interference: Remove External Components: Disconnect external peripherals or sensors to rule out interference or a short circuit. Check Peripheral Initialization: If peripherals are causing issues, ensure that the initialization sequence is correct and that no peripheral is incorrectly blocking the system from starting. Conclusion

By systematically checking the power supply, clock configuration, watchdog settings, boot mode, firmware integrity, reset handling, and external components, you can narrow down the cause of the issue and resolve it effectively. Always proceed with caution when modifying hardware configurations or firmware to avoid causing further issues.