ECE 271 Microcomputer Architecture and Applications University of Maine. Lab 7: Pulse Width Modulation Instructor: Prof. Yifeng Zhu Spring 2016

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1 Lab : Pulse Width Modulation Instructor: Prof. Yifeng Zhu pring Goals. Understand the concept of Pulse Width Modulation (PWM). Use PWM to control the LED brightness Pre-Lab Assignment. Read Chapter. PWM Output. Complete the pin and timer configuration tables Lab Demo. Periodically dimming a LED. Use an oscilloscope to measure duty cycles.. omething cool. Note that dimming another LED does not count as something cool. The following gives a few example of something cool. a. Use PWM to control stepper motors to perform micro-stepping b. Use PWM to generate a music tone (a -Hz sine wave, tone A), or play a song Post-Lab Assignment. Complete the post lab report and write your answer in Readme.md Timer Control for Channel of Timer X: The above diagram shows the functions of each pin. The green LED is connected to the pin PE. The following table shows the alternative functions available for these two pins.

2 LED Pin Available Alternative Functions Green PE TIM_CHN/DFDM_CKIN/FMC_D/AI_CK_B/EVENTOUT Migrating from TML to TML: When you use the flowchart in Figure - (Page of textbook) to program a timer as PWM output, pay attention to the following when configuring the timer. Output Enable OCxN TML OCx output is enabled by the CCxE bit in the TIMx_CCER register. Only has main output OCx but no complementary output OCxN TML OCx output is enabled by a combination of the CCxE, CCxNE, MOE, OI and OR bits (TIMx_CCER and TIMx_BDTR registers). Has both OCx and OCxN. Refer to the following Table for controlling the outputs OCx and OCxN.

3 Play a ong with PWM You can play a song by using a speaker, such as PKMEPP. Murata Electronics PKMEPPH-B peaker (Digikey # --ND) Comments about comments Properly documenting is especially important for assembly programs. Thumb of Rule: If you are able to easily and quickly modify your codes one year after your initial development, then your code comments are excellent. When writing comments, you can assume that readers of your codes know the assembly syntax but do not know your program goals, logic, and methodology. Give meaningful name to registers Recommend to using corresponding C code to make comment Instruction Bad comment Good comment add r, r, # ; add one to a register ; array_index++ sub r, r, # ; r = r - ; counter++ mul r, r, r ; r = r * r ; distance = speed * time pecific Requirements For each subroutine (also called function or procedure), your program should have a comment header. Your program should include a register usage page. Give each register a meaningful name. Here is an example. ; Name: strcat ; Description: Concatenate two strings ; Input: r pointer to the first string ; r pointer to the second string ; Returns: r pointer to the resulting string ; usage: ; r array index i of the second string ; r array index j of the resulting string ; r temporary to hold a char loaded from memory strcat PROC... ENDP

4 Lab : Pre-Lab Assignment NOTE: The Green LED (PE ) is connected the Channel N of Timer.. Configure RCC_AHBENR to enable the clock of GPIO Port E tudent Name: AHBENR RNGEN AEEN ADCEN OTGFEN GPIOPHEN GPIOPGEN GPIOPFEN GPIOPEEN GPIOPDEN GPIOPCEN GPIOPBEN GPIOPAEN Mask Write your assembly code below to enable the GPIO B clock:. Configure RCC_APBENR to enable the clock of Timer APBENR DFDMEN AIEN AIEN TIMEN TIMEN TIMEN UARTEN TIMEN PIEN TIMEN DMMCEN FIREWALLEN TIMEN YCFGEN Mask Write your assembly code below to enable the Timer clock:

5 . Configure PE (Green LED) as Alternative Function Mode GPIO Mode: Input (), Output (), AlterFunc (), Analog () GPIO MODER MODER MODER MODER MODER MODER MODER MODER MODER MODER MODER MODER MODER MODER MODER MODER MODER Mask GPIOE Mode MAK = x (in HEX) GPIOE Mode = x (in HEX). Configure and elect the Alternative Function for PE (Green LED) GPIO AFR[] AFRL[:] AFRL[:] AFRL[:] AFRL[:] AFRL[:] AFRL[:] AFRL[:] AFRL[:] MAK VALUE GPIO AFR[] AFRH[:] AFRH[:] AFRH[:] AFRH[:] AFRH[:] AFRH[:] AFRH[:] AFRH[:] MAK VALUE GPIOE Alternative Function [] MAK = x (in HEX) GPIOE Alternative Function [] = x (in HEX) GPIOE Alternative Function [] MAK = x (in HEX) GPIOE Alternative Function [] = x (in HEX)

6 . Complete the following table to configure the PWM output for Channel N of Timer Note that the alternative function of PE is TIMN, not TIM. You need to set the CCNE bit in the TIM_CCER register. Refer to the table given on Page of the lab handout for controlling OCN. Note that you need to make minor changes to the flow chart given in Figure - (Page of textbook). Offset x TIM_CR UIFREMAP CKD ARPE CM DIR OPM UR UDI CEN x TIM_CR MM[:] OI OI OI OIN OI OIN OI OIN OI TI MM [:] CCD CCU CCPC x TIM_MCR M[] ETP ECE ETP ETF[:] MM T[:] OCC M[:] xc TIM_DIER TDE COMDE CCDE CCDE CCDE CCDE UDE BIE TIE COMIE CCIE CCIE CCIE CCIE UIE x TIM_R CIF CIF BIF CCOF CCOF CCOF CCOF BIF BIF TIF COMIF CCIF CCIF CCIF CCIF UIF x TIM_EGR BG BG TG COM CCG CCG CCG CCG UG TIM_CCMR Output Compare mode OCM[] OCM[] OCCE OCM [:] OCPE OCFE CC OCCE OCM [:] OCPE OCFE CC x TIM_CCMR Input Capture mode ICF[:] IC PC CC ICF[:] IC PC CC TIM_CCMR Output Compare mode OCM[] OCM[] OCCE OCM [:] OCPE OCFE CC OCCE OCM [:] OCPE OCFE CC xc TIM_CCMR Input Capture mode ICF[:] IC PC CC ICF[:] IC PC CC

7 Offset x TIM_CCER CCP CCE CCP CCE CCP CCE CCNP CCNE CCP CCE CCNP CCNE CCP CCE CCNP CCNE CCP CCE x TIM_CNT UIFCPY CNT[:] x TIM_PC PC[:] xc TIM_ARR ARR[:] x TIM_RCR REP[:] x TIM_CCR CCR[:] x TIM_CCR CCR[:] xc TIM_CCR CCR[:] x TIM_CCR CCR[:] x TIM_BDTR BKP BKE BKF[:] BKF[:] MOE AOE BKP BKE OR OI LOC K DT[:] x TIM_DCR DBL[:] DBA[:] xc TIM_DMAR DMAB[:] x TIM_OR TI_RMP ETR_ADC_RMP ETR_ADC_RMP

8 Offset x TIM_CCMR Output Compare mode OCM[] OCM[] OCCE OCM [:] OCPE OCFE OCCE OCM [:] OCPE OCFE x TIM_CCR GCC GCC GCC CCR[:] xc TIM_CCR CCR[:] x TIM_OR ETREL [:] BKCMPP BKCMPP BKINP BKDFBKE BKCMPE BKCMPE BKINE x TIM_OR BKCMPP BKCMPP BKINP BKDFBKE BKCMPE BKCMPE BKINE

9 ECE Microcomputer Architecture and Applications Lab : Pulse Width Modulation Lab Demo Demo : Diming an LED Demo : Use an oscilloscope to measure duty cycles. Keep TIM_ARR fixed but set TIM_CCR to three different s. TIM_ARR = TIM_PC = tudent Name: Case TIM_CCR Pulse Width Measured # TIM_CCR = /* TIM_ARR Pulse Period Measured Duty Cycle Measured # TIM_CCR = /* TIM_ARR # TIM_CCR = /* TIM_ARR ECE Microcomputer Architecture and Applications Lab : Pulse Width Modulation Post-Lab Assignment uppose the HE (high-speed external clock) of MHz is selected the clock of a timer. In order to generate Hz square wave with duty cycle of %, how would set up the timer? Indicate your counting mode and show the of ARR, CRR, and PC registers.

ECE 271 Microcomputer Architecture and Applications University of Maine

ECE 271 Microcomputer Architecture and Applications University of Maine ECE Microcomputer Architecture and Applications Lab : Pulse Width Modulation Instructor: Prof. Yifeng Zhu Spring Goals. Understand the concept of Pulse Width Modulation (PWM). Use PWM to control the LED