Initialize TIM2 Channel 2 for PWM Output in Assembly

[shaw205k]

Posted on March 15, 2014 at 04:00

Hello,

I have a STM32F100RB discovery board and I am trying to setup up TIM2 Channel 2 to output a PWM signal using assembly language, but I am having trouble sorting through the reference manual. The code I have so far to initialize the TIM2 registers is below. This code is part of a larger program that works, so I know my TIM2 initialization is the problem. If someone can point out where I have went wrong it would be greatly appreciated!;TIM2 - Base Addr: 0x4000 0000TIM2_CR1 EQU 0x40000000 ; TIM1 Control Register 1TIM2_CR2 EQU 0x40000004 ; TIM1 Control Register 2TIM2_SMCR EQU 0x40000008 ; TIM1 Slave Mode Control RegisterTIM2_DIER EQU 0x4000000C ; TIM1 DMA/Interrupt Enable RegisterTIM2_SR EQU 0x40000010 ; TIM1 Status RegisterTIM2_EGR EQU 0x40000014 ; TIM1 Event Generation RegisterTIM2_CCMR1 EQU 0x40000018 ; TIM1 Compare/Capture Mode Register 1TIM2_CCMR2 EQU 0x4000001C ; TIM1 Compare/Capture Mode Register 2TIM2_CCER EQU 0x40000020 ; TIM1 Compare/Capture Enable RegisterTIM2_CNT EQU 0x40000024 ; TIM1 CounterTIM2_PSC EQU 0x40000028 ; TIM1 PrescalerTIM2_ARR EQU 0x4000002C ; TIM1 Auto-reload RegisterTIM2_RCR EQU 0x40000030 ; TIM1 Repetition Counter RegisterTIM2_CCR1 EQU 0x40000034 ; TIM1 Capture/Compare Register 1TIM2_CCR2 EQU 0x40000038 ; TIM1 Capture/Compare Register 2TIM2_CCR3 EQU 0x4000003C ; TIM1 Capture/Compare Register 3TIM2_CCR4 EQU 0x40000040 ; TIM1 Capture/Compare Register 4TIM2_BDTR EQU 0x40000044 ; TIM1 Break and Dead-time RegisterTIM2_DCR EQU 0x40000048 ; TIM1 DMA Control RegisterTIM2_DMAR EQU 0x4000004C ; TIM1 DMA Address Register;Registers for config and enabling the clocks;Use Reset and Clock Control Register (RCC) base address = 0x40021000RCC_APB2ENR EQU 0X40021018RCC_APB1ENR EQU 0X4002101C clock_init   ;Enable peripheral clocks for various ports and subsystems ldr R6,=RCC_APB2ENR mov R0, #0x00000A1D ;Enable Alt Fcn IO, GPIO ABC, ADC1, and TIM1 str R0,[R6] ldr R6,=RCC_APB1ENR mov R0, #0x00000001 ;Enable TIM2 Clock str R0,[R6]

gpio_init

ldr R6,= GPIOA_CRL ldr R0,= 0x4444BBB4 ;A1, A2, A3 are alt fcn (PWM)  str R0,[R6] tim2_init ldr R6, = TIM2_CR1 mov R0, #0x01 ;set CEN bit high to start up system str R0, [R6] ldr R6, = TIM2_EGR mov R0, #0x01 ;initialize registers str R0, [R6] ldr R6, = TIM2_CCMR1 mov R0, #0x6C00 ;set OC2M = 110 and OC2PE = 1 and OCPFE = 1 str R0, [R6] ldr R6, = TIM2_CCER mov R0, #0x0001 ;CC2E = 1 str R0, [R6] ldr R6, = TIM2_PSC mov R0, #799 ;divide value to get 10kHz clock into counter str R0, [R6] ldr R6, = TIM2_ARR mov R0, #200 ;Period so that it is 20ms str R0, [R6] ldr R6, = TIM2_CCR2 mov R0, #100 ;PW value  str R0, [R6] ldr R6, = TIM2_CR1 mov R0, #0x01 ;set CEN bit high to start up system str R0, [R6]main PROC ;other code that works... B main ENDP

[Tesla DeLorean]

Posted on March 15, 2014 at 14:33

799? 8 MHz processor?

20 ms from 10 KHz, 200 - 1 You probably want to configure the speed/direction of the pins.

[shaw205k]

Posted on March 17, 2014 at 02:18

Yes the processor is set to 8MHz, and thanks for the adjustment on the period.

When I set the CC2E bit in the TIM2_CCER register I left the CC2P bit (in the same register) as zero to set the polarity to active high. Is this what you mean by the direction of the pin?When you refer to setting the speed of the pin are you referring to the Mode bits that are set when I write to the GPIOB_CRH register? When I write to this register I set the PWM output pin to output mode with a max speed of 50MHz. I can't find any other register that refers to the speed of the pin.