Goals. Grading Rubrics (Total = 20 points) Pre-lab assignment

Transcription

1 Lab : Interfacing Push-button and LED Instructor: Prof. Yifeng Zhu Spring Goals. Get familiar with the Keil uvision software development environment. Create a C project for STML discovery kit and program the kit. Learn basics of GPIO input and output configuration. Perform simple digital I/O input (interfacing push button) and output (interfacing LED). Understand polling I/O (busy waiting) and its inefficiency Grading Rubrics (Total = points). Pre-lab assignment ( points). Documentation and Maintainability ( points). Functionality and Correctness ( points). Lab Demonstration ( points). Something cool ( points) NOTE: Do NOT connect the discovery kit into your PC or laptop before installing the software. Windows might associate the kit with an incorrect USB device driver. Pre-lab assignment. Windows operation system is required. Our development software, Keil uvision, can only run in Windows. If your computer runs Linux or Mac OS, you can install virtual machines.. Download free Keil uvision (MDK-Lite Edition) and install it. It is free but limits your data and code to KB, which is not an issue for all homework and lab assignments in this course.. Follow the tutorial of setting up Gitlab sever. Set up your public and private keys. Read Textbook Chapter. to review bitwise operations.. Read Textbook Chapter GPIO. Lab assignment Following Book Chapter and implement a C program that toggles both Blue and Green LED when the user button is pressed. Do something cool. The following gives a few examples but you are not limited to this. Creative ideas are always encouraged. o Using an oscilloscope to show the voltage output of LED and the voltage signal of the pin connected to the pushbutton. Find out the latency between the button pressed and LED lighting up. o Using the software logic analyzer provided in MDK-KEIL to analyze the digital input and output signals. o Using an oscilloscope to show the GPIO output signal difference when the GPIO have different output speeds. Using GPIO a LED to send out SOS in Morse code ( ) if the user button is pressed. DOT, DOT, DOT, DASH, DASH, DASH, DOT, DOT, DOT. DOT is on for ¼ second and DASH is on for ½ second, with ¼ second between these light-ons.

2 LEDs on the Board There are two LEDs on the STML discovery board, which are connected to the GPIO Port B Pin (PB) and the GPIO Port E Pin (PE) pin of the STML processor, respectively. To light up a LED, software must at least perform the following three operations:. Enable the clock of the corresponding GPIO port. (By default, the clock to all peripherals, including GPIO ports, are turned off in order to improve the energy efficiency.). Set the mode of the corresponding GPIO pin must be set as output, (By default, the mode of all GPIO pin is analog). Set the output value of the corresponding GPIO pin to. (When the output value is, the voltage on the GPIO pin is V. When the output value is, the voltage is V.) The joystick (MT-A) has five keys, including up, down, left, right, and select. Each key has an output pin and all of them are connected to a common pin, as shown below. The joystick is connected to the GPIO pins PA, PA, PA, PA, and PA. A capacitor and a resister are added for each GPIO pin to perform hardware debouncing. Note: At ambient temperature, the GPIOs (general purpose input/outputs) can sink or source up to ± ma.

3 PIN Connections STMLVGT microcontroller featuring Mbyte of Flash memory, and Kbytes of RAM in LQFP package (with pins). The onboard peripherals are connected as follow. Peripheral Peripheral s Peripheral s Pin Peripheral Interface Interface Pin Center PA VLCD PC Left PA COM PA Joystick Right PA COM PA (MT-A) Up PA COM PA Down PA COM PB User LEDs LD Red PB SEG PA LD Green PE SEG PC SAI_MCK PE SEG PB CSL SAI_FS PE SEG PB Audio DAC SAI_SCK PE SEG PB Stereo SAI_SD PE SEG PD IC address IC_SCL PB SEG PD x IC_SDA PB SEG PD Audio_RST PE SEG PD MPDT Audio_DIN PE LCD SEG PC MEMS MIC Audio_CLK PE SEG PA LSMC ecompass LGD Gyro ST-Link V Quad SPI Flash Memory MAG_CS PC SEG PB MAG_INT PC SEG PB MAG_DRDY PC SEG PC MEMS_SCK PD ( SPI_SCK) SEG PC MEMS_MOSI PD ( SPI_MOSI) SEG PD XL_CS PE SEG PD XL_INT PE SEG PD MEMS_SCK PD ( SPI_SCK) SEG PD MEMS_MOSI PD ( SPI_MOSI) SEG PB MEMS_MISO PD ( SPI_MISO) SEG PB GYRO_CS PD SEG PB GYRO_INT PD SEG PC GYRO_INT PB SEG PA USART_TX PD OTG_FS_PowerSwitchOn PC USART_RX PD OTG_FS_OverCurrent PC SWDIO PA OTG_FS_VBUS PC USB OTG SWCLK PA OTG_FS_ID PC SWO PB OTG_FS_DM PA V_REG_ON PB OTG_FS_DP PA QSPI_CLK PE(QUADSPI_CLK) OSC_IN PC QSPI_CS PE(QUADSPI_NCS) OSC_OUT PC Clock QSPI_D PE(QUADSPI_BK_IO) OSC_IN PH QSPI_D PE(QUADSPI_BK_IO) OSC_OUT PH QSPI_D PE(QUADSPI_BK_IO) QSPI_D PE(QUADSPI_BK_IO)

4 Clock Configuration There are two major types of clocks: system clock and peripheral clock. System Clock In order to meet the requirement of performance and energy-efficiency for different applications, the processor core can be driven by four different clock sources, including, HSI (high-speed internal) oscillator clock, HSE (high-speed external) oscillator clock, PLL clock, and MSI (multispeed internal) oscillator clock. A faster clock provides better performance but usually consumes more power, which is not appropriate for battery-powered systems. Peripheral Clock All peripherals require to be clocked to function. However, clocks of all peripherals are turned off by default in order to reduce power consumption. The following figure shows the clock tree of STMLVGT, the processor used in the STML Discovery kit. The clock sources in the domain of Advanced High-performance Bus (AHB), low-speed Advanced Peripheral Bus (APB) and high-speed Advanced Peripheral Bus (APB) can be switched on or off independently when it is not used. Software can select various clock sources and scaling factors to achieve desired clock speed, depending on the application s needs. The software provided in this lab uses the MHz HSI as the input to the PLL clock. Appropriate scaling factors have been selected to achieve the maximum allowed clock speed ( MHz). See the function void System_Clock_Init() for details. void System_Clock_Init(void){... // Enable the Internal High Speed oscillator (HSI) RCC->CR = RCC_CR_HSION; while((rcc->cr & RCC_CR_HSIRDY) == ); RCC->CR &= ~RCC_CR_PLLON; while((rcc->cr & RCC_CR_PLLRDY) == RCC_CR_PLLRDY); // Select clock source to PLL RCC->PLLCFGR &= ~RCC_PLLCFGR_PLLSRC; RCC->PLLCFGR = RCC_PLLCFGR_PLLSRC_HSI; // = No clock, = MSI, = HSI, = HSE // Make PLL as MHz // f(vco clock) = f(pll clock input) * (PLLN / PLLM) = MHz * / = MHz // f(pll_r) = f(vco clock) / PLLR = MHz/ = MHz RCC->PLLCFGR = (RCC->PLLCFGR & ~RCC_PLLCFGR_PLLN) U << ; RCC->PLLCFGR = (RCC->PLLCFGR & ~RCC_PLLCFGR_PLLM) U << ; RCC->PLLCFGR &= ~RCC_PLLCFGR_PLLR; // : PLLR =, : PLLR =, : PLLR =, : PLLR = RCC->PLLCFGR = RCC_PLLCFGR_PLLREN; // Enable Main PLL PLLCLK output RCC->CR = RCC_CR_PLLON; while((rcc->cr & RCC_CR_PLLRDY) == ); // Select PLL selected as system clock RCC->CFGR &= ~RCC_CFGR_SW; RCC->CFGR = RCC_CFGR_SW_PLL; // : MSI, :HSI, : HSE, : PLL // Wait until System Clock has been selected while ((RCC->CFGR & RCC_CFGR_SWS)!= RCC_CFGR_SWS_PLL);

5 Connected to. KHz external crystal oscillator MCOSEL[:] in RCC_CFGR MCOPRE[:] in RCC_CFGR Not populated on the kit HPRE[:] in RCC_CFGR Should be /, MHz MHz SW[:] in RCC_CFGR PPRE[:] in RCC_CFGR MSIRANGE[:] in RCC_CR: : khz : MHz (reset value) : khz : MHz : khz : MHz : khz : MHz : M Hz : MHz : MHz : MHz RCC_PLLCFGR MHz PLLN = MHz PLLSRC[:] in RCC_PLLCFGR PLLM = MHz PLLR = MHz PPRE[:] in RCC_CFGR RCC_PLLSAICFGR MHz PLLSAIN = MHz PLLSAIP =. MHz CLKSEL[:] in RCC_CCIPR RCC_PLLSAICFGR. MHz ADCSEL[:] in RCC_CCIPR SAISEL[:] in RCC_CCIPR SAISEL[:] in RCC_CCIPR Figure modified from STMLxx Datasheet SAI = Serial Audio Interface

6 Each of the GPIO pins can be configured by software as output (push-pull or open-drain), as input (with or without pull-up or pull-down) or as peripheral alternate function. In this lab, we will configure PB and PE as push-pull output. Each general-purpose I/O port x (x = A, B, C,, H) has four -bit configuration registers o GPIOx_MODER (mode register) o GPIOx_OTYPER (output type register) o GPIOx_OSPEEDR (output speed register) o GPIOx_PUPDR (pull-up/pull-down register) two -bit data registers o GPIOx_IDR (input data register) o GPIOx_ODR (output data register) a -bit set/reset register (GPIOx_BSRR). a -bit locking register (GPIOx_LCKR) two -bit alternate function selection registers o GPIOx_AFRH (alternative function high register) o GPIOx_AFRL (alternative function low register)

7 MODE : Input : General purpose output mode : Alternate function mode : Analog mode (Default) OSPEED : Very low speed : Low speed : High speed : Very high speed The data present on the I/O pin are sampled into IDR every AHB clock cycle. PUPDIR : No pull-up, pull-down (Default) : Pull-up : Pull-down : Reserved BSRR allows to set and reset each individual bit in ODR. (atomic bitwise handling) IDR High, if Input > a high threshold Output = Low, if Input < a lower threshold Unchanged, otherwise BSRR ODR Write to BSRR(i): set ODR(i) Write to BSRR(i+SIZE): reset ODR(i) Write to BSRR has no effect on ODR Open drain: A output activates N-MOS whereas a output leaves the port in Hi-Z (P-MOS is never activated) Push-pull: A output register activates N-MOS whereas a output activates P-MOS OTYPE : Output push-pull (Default) : Output open-drain Code Comments and Documentation Program comments are used to improve code readability, and to assist in debugging and maintenance. A general principal is Structure and document your program the way you wish other programmers would (McCann, ). The book titled The Elements of Programming Style by Brian Kernighan and P. J. Plauger gives good advices for beginners.. Format your code well. Make sure it's easy to read and understand. Comment where needed but don't comment obvious things it makes the code harder to read. If editing someone else's code, format consistently with the original author.. Every program you write that you intend to keep around for more than a couple of hours ought to have documentation in it. Don't talk yourself into putting off the documentation. A program that is perfectly clear today is clear only because you just wrote it. Put it away for a few months, and it will most likely take you a while to figure out what it does and how it does it. If it takes you a while to figure it out, how long would it take someone else to figure it out?

8 . Write Clearly - don't be too clever - don't sacrifice clarity for efficiency.. Don t over comment. Use comments only when necessary.. Format a program to help the reader understand it. Always Beautify Code.. Say what you mean, simply and directly.. Don't patch bad code - rewrite it.. Make sure comments and code agree.. Don't just echo code in comments - make every comment meaningful.. Don't comment bad code - rewite it.. The single most important factor in style is consistency. The eye is drawn to something that "doesn't fit," and these should be reserved for things that are actually different.

9 Comparison between STML (used by book) and STML (used in our lab) The book was based on STML board but we are using STML board this semester. They are slightly different. The following table compares the RCC clock setting and GPIO. STML STML Core MHz MHz with FPU and DSP MSI khz, khz, khz, khz,. MHz,. MHz (default value),. MHz khz, khz, khz, khz, MHz, MHz, MHz (default value), MHz, MHz, MHz, MHz and MHz LSI khz khz RC RCC_AHBENR RCC RCC_AHBLPENR (LP = Low Power) RCC_APBENR RCC_APBLPENR (LP = Low Power) RCC_AHBENR (AHB) RCC_AHBENR (AHB) RCC_AHBENR (AHB) RCC_AHBSMENR (AHB) RCC_AHBSMENR (AHB) RCC_AHBSMENR (AHB) (SM = Sleep Mode) RCC_APBENR RCC_APBENR RCC_APBSMENR RCC_APBSMENR (SM = Sleep Mode) RCC_APBENR RCC_APBENR RCC_APBLPENR (LP = Low Power) RCC_APBSMENR (SM = Sleep Mode) GPIO Default mode is Digital Input Default mode is Analog Alternative functions are different. Alternative functions are different. AF SYSTEM AF TIM AF TIM/TIM/TIM AF TIM/TIM/TIM AF IC/IC AF SPI/SPI AF SPI AF USART/ USART/ USART AF UART/UART AF AF USB AF LCD AF FSMC AF AF RI AF EVENTOUT AF SYSTEM AF TIM/TIM/TIM/TIM/LPTIM AF TIM/TIM/TIM/TIM/TIM AF TIM AF IC/IC/IC AF SPI/SPI AF SPI/DFSDM AF USART/USART/ USART AF UART/UART/LPUART AF CAN/TSC AF OTG_FS/QUADSPI AF LCD AF SDMMC/COMP/COMP/FMC/SWPMI AF SAI/SAI AF TIM/TIM/TIM/TIM/LPTIM AF EVENTOUT Add a new register GPIO_ASCR (Analog Switch Control ) : Disconnect analog switch to the ADC input

10 : Connect analog switch to the ADC input typedef struct { IO uint_t MODER; IO uint_t OTYPER; IO uint_t OSPEEDR; IO uint_t PUPDR; IO uint_t IDR; IO uint_t ODR; IO uint_t BSRR; IO uint_t LCKR; IO uint_t AFR[]; IO uint_t BRR; IO uint_t ASCR; } GPIO_TypeDef; For example, to use PA. as analog input: GPIOA->ASCR = U<<;

11 Lab : Pre-Lab Assignment ( points) Spring Student Name: TA: Time & Date:. Enable the clock of GPIO Port A (for joy stick ), Port B (for Red LED) and Port E (for Green LED) AHBENR RNGEN AESEN ADCEN OTGFSEN GPIOPHEN GPIOPGEN GPIOPFEN GPIOPEEN GPIOPDEN GPIOPCEN GPIOPBEN GPIOPAEN Note: Why do we need the mask? When we toggle, set, or reset specific bits of a word ( bytes), we have to keep the other bits of the word unchanged. For example, we want to set bit of the variable aword, the following code is incorrect because it resets all the other bits in this word. aword = ; The correct approach is: aword = ; Typically we use mask to facilitate the operations of toggling, setting or resetting a group of bits in a variable. = x; aword = ; // Set bit and bit aword &= ~; // Reset bit and bit aword ^= ; // Toggle bit and bit

12 . Pin Initialization for Red LED (PB ) a. Configure PB as Output GPIO Mode: Input (), Output (), Alternative Function (), Analog (, default) MODER MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] GPIOB Mode MASK = x (in HEX) GPIOB Mode = x (in HEX) b. Configure PB Output Type as Push-Pull Push-Pull (, reset), Open-Drain () OTYPER OT OT OT OT OT OT OT OT OT OT OT OT OT OT OT OT Reserved GPIOB Output Type MASK = x (in HEX) GPIOB Output Type = x (in HEX) c. Configure PB Output Type as No Pull-up No Pull-down NO PUPD (, reset), Pullup (), Pulldown (), Reserved () PUPDR PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] GPIOB Pull-up Pull-down MASK = x (in HEX) GPIOB Pull-up Pull-down = x (in HEX)

13 . Pin Initialization for Green LED (PE ) a. Configure PE as Output GPIO Mode: Input (), Output (), Alternative Function (), Analog (, default) MODER MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] GPIOE Mode MASK = x (in HEX) GPIOE Mode = x (in HEX) b. Configure PE Output Type as Push-Pull Push-Pull (, reset), Open-Drain () OTYPER OT OT OT OT OT OT OT OT OT OT OT OT OT OT OT OT Reserved GPIOE Output Type MASK = x (in HEX) GPIOE Output Type = x (in HEX) c. Configure PE Output Type as No Pull-up No Pull-down NO PUPD (, reset), Pullup (), Pulldown (), Reserved () PUPDR PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] GPIOE Pull-up Pull-down MASK = x (in HEX) GPIOE Pull-up Pull-down = x (in HEX)

14 . Pin Initialization for Joy Stick a. Configure PA (Center), PA (Left), PA (Right), PA (Up), and PA (Down) as Input GPIO Mode: Input (), Output (), Alternative Function (), Analog (, default) MODER MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] MODER[:] GPIOA Mode MASK = x (in HEX) GPIOA Mode = x (in HEX) b. Configure PA (Center), PA (Left), PA (Right), PA (Up), and PA (Down) as Pulldown NO PUPD (, reset), Pullup (), Pulldown (), Reserved () PUPDR PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] PUPDR[:] GPIOE Pull-up Pull-down MASK = x (in HEX) GPIOE Pull-up Pull-down = x (in HEX)

15 Lab : Lab Demo You should be able to correctly answer the following questions to TAs.. Why did we configure the pins that drive the LEDs (PB and PE ) as push-pull instead of open-drain?. What is GPIO speed? What is the default speed? Did you notice any difference of you choose different speeds in this lab assignment?. Show TA that you can toggle a LED in the debug environment by directly changing the value of the Output Data (ODR) of a GPIO port. Lab : Lab Code Submission. Submit and maintain your code in gitlab server. Make sure to comment your codes appropriately. Make sure to complete the Readme.Md file Lab : Post-Lab Assignment ( point). The joy stick on the STML board has a hardware debouncing circuit. The following is one example debouncing circuit. Explain briefly how the hardware debouncing circuit works. Find out a typical solution for software debouncing. Vdd nf Push Button PA Ω KΩ Place your answer to this question in the file Readme.md Submit it to the Gitlab Server. If you have figures/images, you can put your answer in a word document, and put a note in Readme.md. Make sure to perform git add to the word document.