STM32F0DISCOVERY peripheral firmware examples
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1. CT AN4062 YI a a Application note STM32FODISCOVERY peripheral firmware examples March 2013 Introduction This application note describes the peripheral firmware examples provided for the STM32FODISCOVERY Kit These ready to run examples are provided to help the user get started quickly with STM32F0xx peripherals and STM32FODISCOVERY board hardware Preconfigured projects for EWARM IAR Embedded Workbench for ARM MDK ARM Atollic TrueSTUDIO and Altium TASKING toolchains are provided for each example These examples are included in the firmware applications package available for download on www st com stm32f0discovery Users are advised to first read the document Getting started with software and firmware environments for the STM32FODISCOVERY Kit UM1523 to familiarize themselves with the STM32FODISCOVERY Kit Table 1 lists the microcontrollers and development tools concerned by this application note Table 1 Applicable products and tools Type Part numbers and product categories Microcontrollers STM32F0 series Development tools STM32FODISCOVERY Software STSW STM32049 DoclD022897 Rev 3 1 17 www st com Contents AN4062 Contents 1 Peripheral firmware examples structure overview 3 2 Glock Configuration lt 06 i2cececenetccek eevee eladebeeecdous 4 2 1 PLE SOURCE Sl 2vuceserure er tiene KA BALANGA DAG ae Yeas ANNA 4 2 2 PLL SOURCE HSE paien n ata e atl Beh ag2. the wakeup from low power mode is automatically generated by the RTC after 5s In Sleep mode and Standby mode press again the User button to exit the low power mode The different low power mode configurations are Sleep mode System running at PLL 48 MHz Flash 3 wait state Code running from Internal Flash All peripherals disabled Wakeup using EXTI Line User push button PA 00 Stop mode RTC clocked by LSI Regulator in LP mode HSI HSE OFF and LSI if not used as RTC clock source NoIWDG Flash in deep power down mode Automatic Wakeup using RTC clocked by LSI Standby mode RTC OFF IWDG and LSI OFF Wakeup using Wakeup Pin PA 00 Standby mode with RTC clocked by LSI RTC clocked by LSI IWDG OFF and LSI OFF if not used as RTC clock source Automatic Wakeup using RTC clocked by LSI Flash program example Purpose This example describes how to program the STM32FOxx internal Flash Description In this example After Reset the Flash memory Program Erase Controller is locked The FLASH_Unlock function is used to unlock it Before programming the desired addresses an erase operation is performed using the Flash erase sector feature The erase procedure starts with the calculation of the DoclD022897 Rev 3 ky AN4062 Peripheral firmware examples description number of sectors to be used These sectors are erased one by one by calling the FL
3. TIM1 CCR4 register value is equal to 431 so the TIM1 Channel 4 generates a PWM signal with a frequency equal to 17 57 kHz and a duty cycle equal to 12 5 TIM1 Channel4 duty cycle TIM1_CCR4 TIM1 ARR 1 100 12 5 The PWM waveform can be displayed using an oscilloscope Connect the TIM1 pins to an oscilloscope to monitor the different waveforms e TIM1 CH1 pin PA 08 e TIM1 CH2 pin PA 09 e TIM1 CH3 pin PA 10 e TIM1 CH4 pin PA 11 lt lt mH Timer ADC trigger example Purpose This example describes how to configure the TIM to trigger the ADC conversion Description In this example the TIM1 is configured in PWM mode the TIM1 CC4 event is used to trigger the ADC The ADC is configured to convert continuously the ADC_Channel_11 connected to an external voltage Each time the TIM1 CC4 event occurs the ADC converts the variable voltage Connect the external signal ranges between 0 and 3 3V to ADC pin PC 01 NVIC WFI mode example Purpose This example shows how to enter the WFI mode and wake up from this mode by the User key interrupt DoclD022897 Rev 3 hy AN4062 Peripheral firmware examples description Note 3 20 Description In the associated software the system clock is set to 48 MHz When the user presses the User Key Button the MCU enters the WFI mode If the user presses again the User Key Button LED3 is toggled with a frequency depending on the system clock This is u
4. chad a E eee E a a 4 2 3 PLL_SOURCE_HSE_BYPASS 0 ccie ices aa se a 4 3 Peripheral firmware examples description 5 3 1 GPIO toggle example oes cup weds cee Acar eee ee Pah eee ee ee 5 3 2 EXTI example 2 2 2222 eee 5 3 3 S s lick example sass aaiae ewok oe hEe BA beets eee ube ie Pha nG 5 3 4 Standby mode example cee ees 6 3 5 Stop mode example cece eee 7 3 6 Current consumption example 2 7 3 7 Flash program example 2222 00 eeeeeeeeeeeeee 8 3 8 IWDG independent watchdog example eee ee eee 9 3 9 ADC DMA example 0 0000 ce eee eens 9 3 10 ADC low power example 0000000 10 3 11 DMA Flash RAM example 22 2 000 e eee eee 10 3 12 DMA RAM DAC example 2 0c ee 11 3 13 DAC signal generation example a 11 3 14 TIM complementary signal example a 11 3 15 TIM time base example 00000 cee ee 12 3 16 TIM PWM input example 0 000000 13 3 17 TIMPWM output example 2 00000 eee 13 3 18 Timer ADC trigger example 02 es 14 3 19 NVIC WFI mode example 2 0000000 14 3 20 RCC reset and clock control example aa 15 4 Revision history 2473aaa kaaa a wu TERENA NGA wove bes BAKA AA 16 2 17 DoclD022897 Rev 3 ky AN4062 Peripheral firmware examples structure overview 1 Peripheral firmware examples structure overview The peripheral firmware exa
5. is toggled this is used to indicate whether the MCU is in STANDBY or RUN mode e The EXTI line O is configured to generate an interrupt on each rising falling edge detected on the PAO pin The external interrupt is generated every time the PAO changes levels GND or VDD When a falling or rising edge is detected on the EXTI line an interrupt is generated In the EXTI handler routine the RTC is configured to generate an Alarm event in 3 seconds after which the system enters the Standby mode and LED3 is Off After wake up from Standby mode the program execution restarts in the same way as after a reset the RTC configuration clock source prescaler is kept and LED3 is toggling again As a result there is no need to configure the RTC LED3 is used to monitor the system state as following e LED3 toggling system in RUN mode e LED3 off system in STANDBY mode e LED3 toggling system resumed from STANDBY mode These steps are repeated in an infinite loop DoclD022897 Rev 3 ky AN4062 Peripheral firmware examples description 3 5 Stop mode example Purpose This example shows how to enter the system to STOP mode and wake up using EXTI Line interrupts The EXTI Line sources are PA O and RTC Alarm Description In this example e The EXTI Line0 is configured to generate interrupt on falling edge e The EXTI line17 RTC Alarm is configured to generate interrupt on rising edge e The SysTick is programmed to generat
6. products with provisions different from the statements and or technical features set forth in this document shall immediately void any warranty granted by ST for the ST product or service described herein and shall not create or extend in any manner whatsoever any liability of ST ST and the ST logo are trademarks or registered trademarks of ST in various countries Information in this document supersedes and replaces all information previously supplied The ST logo is a registered trademark of STMicroelectronics All other names are the property of their respective owners 2013 STMicroelectronics All rights reserved STMicroelectronics group of companies Australia Belgium Brazil Canada China Czech Republic Finland France Germany Hong Kong India Israel Italy Japan Malaysia Malta Morocco Philippines Singapore Spain Sweden Switzerland United Kingdom United States of America www st com ky DoclD022897 Rev 3 17 17
7. 5 The channel 3 duty cycle is set to 12 5 so channel 3N is set to 87 5 The Timer pulse is calculated as follows e ChannelxPulse DutyCycle TIM1_Period 1 100 A dead time equal to 11 SystemCoreClock is inserted between the different complementary signals and the Lock level 1 is selected The break Polarity is used at High level The TIM1 waveform can be displayed using an oscilloscope e Connect the TIM1 pins to an oscilloscope to monitor the different waveforms TIM1_CH1 pin PA 08 TIM1 CHIN pin PB 13 TIM1_CH2 pin PA 9 TIM1_CH2N pin PB 14 TIM1_CHS3 pin PA 10 TIM1_CHS3N pin PB 15 e Connect the TIM1 break pin TIM1_BKIN pin PB 12 to the GND To generate a break event switch this pin level from OV to 3 3V TIM time base example Purpose This example shows how to configure the TIM peripheral in Output Compare Timing mode with the corresponding Interrupt requests for each channel in order to generate 2 different time bases Description The TIM3CLK frequency is set to SystemCoreClock Hz to get TIM3 counter clock at 6 MHz so the Prescaler is computed as follows e Prescaler TIM3CLK TIM3 counter clock 1 e SystemCoreClock is set to 48 MHz e The TIM3 CC3 register is equal to 13654 CC3 update rate TIM3 counter clock CCR3_Val 439 4 Hz Thus the TIM3 Channel 3 generates an interrupt every 2 27 ms e The TIM3 CC4 register is equal to 6826 CC4 update rate TI
8. ASH_EraseSector function e The programming operation is performed by using the FLASH ProgramWord function The written data is then checked and the result of the programming operation is stored in the MemoryProgramStatus variable 3 8 IWDG independent watchdog example Purpose This example shows how to update the IWDG reload counter at regular periods and how to simulate a software fault generating an MCU IWDG reset on expiry of a programmed time period Description In this example e The independent watchdog timeout is set to 250 ms e The system tick is configured to generate an interrupt every 250 ms e In the system tick interrupt service routine the independent watchdog counter is reloaded to prevent an independent watchdog reset and LED4 is toggled e The EXTI line O connected to PAO pin is configured to generate an interrupt on its falling edge e Inthe NVIC this EXTI line O corresponding interrupt vector is enabled with a priority equal to O and the systick interrupt vector priority is set to 1 EXTI interrupt is prior to systick interrupt e The EXTI line is used to simulate a firmware failure when the EXTI line event is triggered after pressing the User push button on the STM32FODISCOVERY board the corresponding interrupt is serviced In the ISR LED3 turns off and the EXTI line pending bit is not cleared The CPU executes the EXTI line ISR indefinitely and the system tick interrupt routine is never entered so th
9. M3 counter clock CCR4_Val 878 9 Hz Thus the TIM3 Channel 4 generates an interrupt every 1 13 ms When the counter value reaches the Output compare registers values the Output Compare interrupts are generated and in the handler routine 2 LEDs LED3 and LED4 connected to PC08 and PCO9 are toggled with the following frequencies LED3 PCO09 219 7 Hz CC3 LED4 PC08 439 4 Hz CC4 DoclD022897 Rev 3 hy AN4062 Peripheral firmware examples description 3 16 Note 3 17 TIM PWM input example Purpose This example shows how to use the TIM peripheral to measure the frequency and duty cycle of an external signal Description The TIMxCLK frequency is set to SystemCoreClock the Prescaler is 0 so the counter clock is SystemCoreClock SystemCoreClock is set to 48 MHz for STM32F0xx Devices TIM2 is configured in PWM Input Mode the external signal is connected to TIM2 Channel2 used as an input pin To measure the frequency and the duty cycle we use the TIM2 CC2 interrupt request so that the frequency and the duty cycle of the external signal are computed In the TIM2 IRQHandler routine The Frequency variable contains the external signal frequency e TIM2 counter clock SystemCoreClock e Frequency TIM2 counter clock TIM2 CCR2 in Hz The DutyCycle variable contains the external signal duty cycle DutyCycle TIM2_CCR1 100 TIM2_CCR2 in The minimum frequency value to measur
10. P2 to measure the Ipp current DMA Flash RAM example Purpose This example describes how to use a DMA channel to transfer a word data buffer from a Flash memory to an embedded SRAM memory Description DMA1 Channel1 is configured to transfer the contents of a 32 word data buffer stored in the Flash memory to the reception buffer declared in RAM e The start of transfer is triggered by software DMA1 Channel1 memory to memory transfer is enabled Source and destination address incrementing is also enabled e The transfer is started by setting the Channel enable bit for DMA1 Channel1 e Atthe end of the transfer a Transfer Complete interrupt is generated since it is enabled Once the interrupt is generated the remaining data to be transferred is read which must be equal to 0 The Transfer Complete Interrupt pending bit is then cleared A comparison between the source and destination buffers is done to check that all data have been correctly transferred DoclD022897 Rev 3 hy AN4062 Peripheral firmware examples description 3 12 DMA RAM DAC example Purpose This example provides a description of how to use a DMA channel to transfer data buffer from RAM memory to DAC Description DMA1 channels is configured to transfer continuously word by word a Half word buffer to the DAC register DAC_DHR12R The DAC channel conversion is configured to be triggered by TIM2 TRGO triggers and without noise triangle wave generation 12 bit right da
11. e an interrupt every 250 ms In the SysTick interrupt handler LED3 is toggled which indicates whether the MCU is in Stop or Run mode The system enters the Stop mode and waits for the RTC Alarm to be generated every 5s or when the User push button is pressed Ifthe RTC Alarm EXTI Line17 is the source of wakeup from Stop LED3 is toggled Ifthe User push button EXTI Line0 is the source of wakeup from Stop LED4 is on and LED3 is toggled LEDs are used to monitor the system state LEDS toggling system in Run mode system woken up from Stop using RTC ALARM LED4 on system woken up from Stop using EXTI Line0 User push button 3 6 Current consumption example Purpose This example shows how to configure the STM32F0xx system to measure different low power modes current consumption The low power modes are e Sleep mode e Stop mode with RTC e Standby mode with wake up pin without RTC e Standby mode with RTC To select the low power modes to be measured uncomment the corresponding line inside the stm32f0xx Ip modes h file Note STM32F0xx consumption can be measured on the STM32FODISCOVERY board by removing jumper JP2 labeled IDD and connecting an ammeter DoclD022897 Rev 3 7117 Peripheral firmware examples description AN4062 3 7 8 17 Description After reset the program waits for the User button connected to PA 00 to be pressed to enter the selected low power mode When the RTC is used
12. e independent watchdog counter is not reloaded As a result when the independent watchdog counter reaches 00 the independent watchdog generates a reset When the program is running and the independent watchdog reset is generated LED4 is turned on after the system resumes operation 3 9 ADC DMA example Purpose This example describes how to use ADC1 and DMA to transfer continuously converted data from ADC1 to memory DoclD022897 Rev 3 9 17 Peripheral firmware examples description AN4062 3 10 Note Note 3 11 10 17 Description In this example e ADC1 is configured to convert continuously the Voltage reference and the Temperature sensor Each time an end of conversion occurs the DMA transfers in circular mode the converted data from ADC1 DR register to the RegularConvData_Tab 2 table ADC low power example Purpose This example provides a short description of how to use the ADC peripheral with Auto delayed conversion mode and Auto poweroff modes Description The ADC is triggered by TIM3 TRGO which is connected to TIM3 Update Event Each time the ADC is triggered it converts the input voltage connected to PC 1 which corresponds to ADC channel 11 and then the ADC enter the delay mode no Overrun detect until the ADC data register has been read by pressing the USER button Connect the external signal ranges from O to 3 3V to the ADC1 pin PC 01 to be converted Connect an ammeter to J
13. e is 732 Hz TIM2 counter clock CCR MAX Connect the external signal to measure the TIM2 CH2 pin PA 01 TIM PWM output example Purpose This example shows how to configure the TIM1 peripheral to generate PWM signals with 4 different duty cycles 50 37 5 25 and 12 5 Description The TIMxCLK frequency is set to SystemCoreClock the Prescaler is 0 so the counter clock is SystemCoreClock SystemCoreClock is set to 48 MHz for STM32F0xx Devices DoclD022897 Rev 3 13 17 Peripheral firmware examples description AN4062 Note 3 18 Note 3 19 14 17 The objective is to generate a PWM signal at 17 57 KHz TIM1_Period SystemCoreClock 17570 1 TIM1 Frequency TIM1 counter clock ARR 1 48 MHz 2730 17 57 kHz e The TIM1 CCR1 register value is equal to 1364 so the TIM1 Channel 1 generates a PWM signal with a frequency equal to 17 57 kHz and a duty cycle equal to 50 TIM1 Channel duty cycle TIM1_CCR1 TIM1_ARR 1 100 50 e The TIM1 CCR2 register value is equal to 1023 so the TIM1 Channel 2 generates a PWM signal with a frequency equal to 17 57 kHz and a duty cycle equal to 37 5 TIM1 Channel2 duty cycle TIM1_CCR2 TIM1_ARR 1 100 37 5 e The TIM1 CCR3 register value is equal to 682 so the TIM1 Channel 3 generates a PWM signal with a frequency equal to 17 57 kHz and a duty cycle equal to 25 TIM1 Channel3 duty cycle TIM1_CCR3 TIM1_ARR 1 100 25 e The
14. lure You can monitor the system clock on MCO pin PA 8 Two LEDs are toggled with a timing defined by the Delay function DoclD022897 Rev 3 15 17 Revision history AN4062 4 16 17 Revision history Table 2 Document revision history Date Revision Changes 23 Mar 2012 1 Initial release 14 May 2012 2 Section 2 Clock configuration added 28 Mar 2013 3 Updated Table 1 Applicable products and tools and Section 3 1 GPIO toggle example DoclD022897 Rev 3 3 AN4062 Please Read Carefully Information in this document is provided solely in connection with ST products STMicroelectronics NV and its subsidiaries ST reserve the right to make changes corrections modifications or improvements to this document and the products and services described herein at any time without notice All ST products are sold pursuant to ST s terms and conditions of sale Purchasers are solely responsible for the choice selection and use of the ST products and services described herein and ST assumes no liability whatsoever relating to the choice selection or use of the ST products and services described herein No license express or implied by estoppel or otherwise to any intellectual property rights is granted under this document If any part of this document refers to any third party products or services it shall not be deemed a license grant by ST for the use of such third party product
15. mples are provided within the STM32FODISCOVERY firmware applications package and are located in the Project folder as shown in Figure 1 Figure 1 Hardware environment 5 B STM32FO Discovery PW VX Y Z O _htmresc O Libraries O Project E Demonstration O Master_Workspace a B Peripheral_Examples O ADC DMA O ADC_LowPower O DAC_SignalsGeneration O DM4_FLASH_RAM O DMA RAM DAC D ext O Flash Program O I0 Toggle O IWDG Reset O MIC WFI Mode O PWR_CurrentConsumption OO PWR_STANDBY O PWR STOP B Rec CD Systick O TIM ADC Trigger O TIM Complementary signals O TIM PWM Input O TIM PWM Output O TIM TimeBase O Utilities HEHEH HEHHE H DH HEHE 1 VX Y Z refer to the package version for example V1 0 0 To run an example open the project with your preferred toolchain compile load and run it Some examples may require additional hardware such as an oscilloscope For further detail about the required hardware refer to the readme file provided within each example 4 DoclD022897 Rev 3 3 17 Clock configuration AN4062 2 2 1 Note 2 2 2 3 4117 Clock configuration The peripheral examples provided within STM32F0 Discovery Kit Firmware package are configured to run at 48 MHz using HSI as the clock source However the user can modify this configuration to use HSE crystal or bypass mode as the clock source which needs some hardware modification on the discove
16. pressed e In the NVIC nested vectored interrupt controller the EXTI line O interrupt priority is configured and the interrupt is enabled When the program is executed and the user pushes on the User push button EXTIO interrupt routine LED3 and LED4 connected to PC9 and PC8 are toggled SysTick example Purpose This example shows how to configure the system tick timer and use it to generate a 1 ms time base DoclD022897 Rev 3 5 17 Peripheral firmware examples description AN4062 3 4 6 17 Description In this example e The system tick timer is initialized e The system tick timer interrupt is enabled in the NVIC e The system tick timer counter starts in free running mode to generate periodical interrupts e The system tick timer interrupt is triggered every 1 ms e A Delay function is implemented based on the system tick timer end of count event The two LEDs LED3 and LED4 are toggled with a timing defined by the Delay function Standby mode example Purpose This example shows how to put the system in Standby mode and wake it up from this mode using the external reset RTC Alarm A Description In this example e The system tick timer is initialized e The system tick timer interrupt is enabled in the NVIC e The system tick timer counter starts in free running mode to generate periodical interrupts The system tick timer interrupt is triggered every 250 ms In the SysTick interrupt handler LED3
17. ry kit hardware The system stm32f0xx c file provided within each example was customized for use with the discovery kit allowing the user to select one of the three configurations below by un commenting the adequate define PLL SOURCE HSI The HSI clock signal is generated from an internal 8 MHz RC Oscillator and can be used directly as a system clock or divided by 2 to be used as a PLL input The HSI RC oscillator has the advantage of providing a clock source at low cost no external components It also has a faster startup time than the HSE crystal oscillator However even with a calibration the frequency is less accurate than an external crystal oscillator or a ceramic resonator This is the default configuration PLL_SOURCE_HSE The high speed external clock signal HSE can be generated from two possible clock sources e HSE external crystal ceramic resonator e HSE user external clock The HSE crystal is not provided with the discovery kit Some hardware modifications are necessary to connect this crystal For more details refer to section 4 7 OSC clock in STM32F0 discovery kit User manual UM1525 PLL_SOURCE_HSE_BYPASS In this mode the HSE is bypassed with an external clock fixed at 8 MHz coming from ST Link circuit It is used to clock the PLL and the PLL is used as the system clock source Some hardware modifications are necessary to bypass the HSE with the clock coming from the ST Link circ
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19. sed to indicate whether the MCU is in WFI or RUN mode e Pressing the key push button generates a rising edge on EXTI Line0 will put the core in the WFI mode causing the LED3 to stop toggling e To wake up from the WFI mode you have to press again the button it generates an interrupt which exits the system from the WFI mode LED3 restarts toggling Press the User button to enter and exit the WFI mode RCC reset and clock control example Purpose This example shows how to e Configure the HSE High Speed Clock as an RCC clock e Use the Clock Security System CSS feature to generate an NMI interrupt e Output the system clock on MCO Description For debug purposes the RCC_GetClocksFreq function is used to retrieve the current status and frequencies of different on chip clocks You can see the RCC_ClockFreq structure content which holds the frequencies of different on chip clocks using your toolchain debugger This example also handles the High Speed External clock HSE failure detection when the HSE clock disappears broken or disconnected external Quartz HSE and PLL are disabled but no change to PLL configuration HSI is selected as a system clock source and an interrupt NMI is generated In the NMI ISR the HSE and HSE ready interrupt are enabled Once the HSE clock recovers the HSERDY interrupt is generated and in the RCC ISR routine the system clock is reconfigured to its previous state before HSE clock fai
20. ta alignment is selected since we choose to access the DAC_DHR12R register Note Connect PA 04 pin to an oscilloscope 3 13 DAC signal generation example Purpose This example provides a short description of how to use the DAC peripheral to generate several signals using the DMA controller Description When the user presses the push button DMA transfers the selected waveform to DAC e For each press on the push button one signal has been selected and monitored on the DAC Channel 1 e Escalator waveform Channel 1 e Sine waveForm Channel 1 Note Use the push button connected to PAO Note Connect PA4 DAC Channel1 pin to an oscilloscope to monitor the DAC out wave 3 14 TIM complementary signal example Purpose This example shows how to configure the TIM1 peripheral to generate three complementary TIM1 signals to insert a defined dead time value to use the break feature and to lock the desired parameters Description TIM1CLK is fixed to SystemCoreClock the TIM1 Prescaler is equal to 0 so the TIM1 counter clock used is SystemCoreClock 48 MHz The objective is to generate a PWM signal at 17 57 KHz e TIM1 Period SystemCoreClock 17570 1 DoclD022897 Rev 3 11 17 Peripheral firmware examples description AN4062 3 15 12 17 The Three Duty cycles are computed as follows The channel 1 duty cycle is set to 50 so channel 1N is set to 50 The channel 2 duty cycle is set to 25 so channel 2N is set to 7
21. uit For more details refer to section 4 7 OSC clock in STM32F0 discovery kit User manual UM1525 DoclD022897 Rev 3 hy AN4062 Peripheral firmware examples description 3 3 1 3 2 3 3 Peripheral firmware examples description GPIO toggle example Purpose This example describes how to use BSRR and BRR Port Bit Set Reset Register High and Low for maximum I O toggling GPIO ports are connected on the AHB bus using BSRR and BRR registers two cycles are required to set a pin and another two cycles to reset it So GPIO pins can toggle at AHB clock divided by 4 Description In this example PC8 and PC9 configured in push pull output mode toggle in a forever loop e Set PC8 and PC9 by setting corresponding bits in BSRR register e Reset PC8 and PC9 by setting corresponding bits in BRR register In this example HCLK is configured at 48 MHz so PC8 and PC9 toggle at 12 MHz To achieve the maximum I O toggling frequency you have to configure your compiler options for high speed optimization EXTI example Purpose This example shows how to configure an external interrupt line Description In this example e PAQ pin is configured in input floating e PAD is configured to be used as an external interrupt source line O EXTIO e The EXTI line O is configured to generate an interrupt on each rising edge detected on the PAO pin The interrupt is triggered every time the User push button is
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