Other Parts Discussed in Thread: TM4C123GH6PM
Hi,
I am trying to control a EV3 Lego motor uning the TIVA Launchpad. I want to use the PWM functionality of the microcontroler. I am folllowng instructions from page 1230 from TM4C123GH6PM_April2013.
I have seen some discussion regarding the issue, but none of the solutions seem to work. Here is my code:
//====PWM.c file===
// PWM.c
// Runs on TM4C123
// A Software function to configure the M0PWM0 in PB6, to be used to control a single motor using L298 using
// implemented PWM in microcontroler
// Port B is also initialized in order to control other features in L298
// Wiring to L298
// PB6 is PWM signal to control motor velocity
// Motor A truth table
// PB6 PB1 PB0 Microcontroler pins
// ENA IN1 IN2 Description
// 0 N/A N/A Motor A is off
// 1 0 0 Motor A is stopped (brakes)
// 1 0 1 Motor A is on and turning backwards
// 1 1 0 Motor A is on and turning forwards
// 1 1 1 Motor A is stopped (brakes)
// Joan Sans
// 31 May 2016
#include "PWM.h"
#include "C:/Keil/Joan/JOAN_UTILS/tm4c123gh6pm.h"
void PortB_Init(void){ volatile unsigned long delay;
SYSCTL_RCGC2_R |= 0x00000002; // 1) activate clock for Port B: Already activated in PWM init
delay = 0x00000020; //SYSCTL_RCGC2_R;//When initializing port F we write a 0x20 but now it would be a0x02, so I set to 0x20. allow time for clock to start
GPIO_PORTB_LOCK_R = 0x4C4F434B; // 2) unlock GPIO Port B. To unlock all ports send 0x4C4F434B.
GPIO_PORTB_CR_R = 0x3F; // allow changes to PB5-0
GPIO_PORTB_AMSEL_R = 0x00; // 3) disable analog on PB
GPIO_PORTB_PCTL_R = 0x04000000; //PMC6 = 4 to configure M0PMW0
GPIO_PORTB_DIR_R = 0x3F; // 5) PB5 to PB0 out
GPIO_PORTB_AFSEL_R = 0x40; //Enable alternate functions for PB6. Dissable for the rest
GPIO_PORTB_PUR_R = 0x00; // disable pull-up on PB5-0
GPIO_PORTB_DEN_R = 0x3F; // 7) enable digital I/O on PB5-0
}
void PWM_Init(void){
// Initialization and Configuration
// The following example shows how to initialize PWM Generator 0 with a 25-kHz frequency, a 25%
// duty cycle on the MnPWM0 pin, and a 75% duty cycle on the MnPWM1 pin. This example assumes
// the system clock is 20 MHz.
// 1. Enable the PWM clock by writing a value of 0x0010.0000 to the RCGC0 register in the System
// Control module (see page 452). ATENTION: RCGCO is legacy. RCGCPWM should be used instead.
SYSCTL_RCGCPWM_R &= 0x00000001; //activate PWM0
// 2. Enable the clock to the appropriate GPIO module via the RCGC2 register in the System Control
// module (see page 460).
SYSCTL_RCGC2_R |= 0x00000002; //activate clock for Port B
// 3. In the GPIO module, enable the appropriate pins for their alternate function using the
// GPIOAFSEL register. To determine which GPIOs to configure, see Table 23-4 on page 1334.
GPIO_PORTB_AFSEL_R = 0x40; // Enable alternate functions for PB6. Dissable for the rest
// 4. Configure the PMCn fields in the GPIOPCTL register to assign the PWM signals to the appropriate
// pins (see page 682 and Table 23-5 on page 1341).
GPIO_PORTB_PCTL_R |= 0x04000000; //PMC6 = 4 to configure M0PMW0
// 5. Configure the Run-Mode Clock Configuration (RCC) register in the System Control module
// to use the PWM divide (USEPWMDIV) and set the divider (PWMDIV) to divide by 2 (000).
SYSCTL_RCC_R |=0x00100000; //RCC bit20=1(USEPWMDIV)
SYSCTL_RCC_R &=0xFFF1FFFF; //RCC bit17-19=000PWMDIV) to divide by 2 (000)
// 6. Configure the PWM generator for countdown mode with immediate updates to the parameters.
// ¦ Write the PWM0CTL register with a value of 0x0000.0000.
PWM0_0_CTL_R = 0x00000000; //
// ¦ Write the PWM0GENA register with a value of 0x0000.008C.
PWM0_0_GENA_R = 0x0000008C; //
// ¦ Write the PWM0GENB register with a value of 0x0000.080C.
PWM0_0_GENB_R = 0x0000080C;
// 7. Set the period. For a 25-KHz frequency, the period = 1/25,000, or 40 microseconds. The PWM
// clock source is 10 MHz; the system clock divided by 2. Thus there are 400 clock ticks per period.
// Use this value to set the PWM0LOAD register. In Count-Down mode, set the LOAD field in the
// PWM0LOAD register to the requested period minus one.
// ¦ Write the PWM0LOAD register with a value of 0x0000.018F.
// For 80 MHz, clock source is 40 MHz. Then there is 1600 clock ticks per period
PWM0_0_LOAD_R = 0x63F; //0x63F = 1599
// 8. Set the pulse width of the MnPWM0 pin for a 25% duty cycle.
// ¦ Write the PWM0CMPA register with a value of 0x0000.012B.
PWM0_0_CMPA_R = 0x4AF; //0x4AF = 1199
// 9. Set the pulse width of the MnPWM1 pin for a 75% duty cycle.
// ¦ Write the PWM0CMPB register with a value of 0x0000.0063.
PWM0_0_CMPB_R = 0x18F; //0x18F = 399
// 10. Start the timers in PWM generator 0.
// ¦ Write the PWM0CTL register with a value of 0x0000.0001.
PWM0_0_CTL_R = 0x00000001;
// 11. Enable PWM outputs.
// ¦ Write the PWMENABLE register with a value of 0x0000.0003.
// PWM0_ENABLE_R = 0x00000003;
};
I get trouble when line starting with PWM0_0_GENA_R is executed.
Does anybody have an idea on what is going on?
Thanks in advance
Joan S.
