Hi,
I'm a third year triple E student who's decided to try and learn the M4/stellaris architecture. I've had some experience with the motorola HCS08 but I find the API approach for this processor a bit confusing. I've only had the launchpad board for a couple of days but I've been following the TI labs and after completing lab4 - interrupts decided to try and drive the RGB led with PWM.
I've got the following code which almost works - all I'm trying to do at the minute is fade in each of the colours. I can get each of the colours to fade in individually, if i comment out all of the timer setup for the colours I'm not using, but if I try to fade all three in at the same time I get some weird behaviour - the colour is an off green (looking through the header files for the qs-rgb I've realised this is because "true white" is not 100% R,G,B) and there is no discernable fading - the LED is just instantly on.
Also, red and blue fade in reasonably reliably by themselves, but the green will fade in once, and if I reset the board the LED will not turn on again. I can fix this problem by uncommenting all of the timer setup, running it, and then commenting out the colours I don't want to use again, which leads me to think there must be something inherently wrong with my understanding of how to set up the timers - I remember reading a few times in the datasheet things like you must make sure to set x bit before writing to y register, or do not enable a peripheral before you've configured it - so I'm assuming I may be missing some critical understanding in an area such as this. The code I'm using is below - can anyone see any glaring errors in my approach?
#include "inc/hw_ints.h"
#include "inc/hw_memmap.h"
#include "inc/hw_types.h"
#include "driverlib/sysctl.h"
#include "driverlib/interrupt.h"
#include "driverlib/gpio.h"
#include "driverlib/timer.h"
#include "driverlib/pin_map.h"
int main(void)
{
unsigned long ulPeriod;
unsigned long dutyCycleRed;
unsigned long dutyCycleBlue;
unsigned long dutyCycleGreen;
ulPeriod = 1000;
dutyCycleRed = ulPeriod;
dutyCycleBlue = ulPeriod;
dutyCycleGreen = ulPeriod;
SysCtlClockSet(SYSCTL_SYSDIV_5|SYSCTL_USE_PLL|SYSCTL_XTAL_16MHZ|SYSCTL_OSC_MAIN);
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
GPIOPinTypeGPIOOutput(GPIO_PORTF_BASE, GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3);
GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3, 0 ); //added this because green led was on regardless of PWM configuration
//red pin setup
SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER0);
TimerConfigure(TIMER0_BASE, TIMER_CFG_SPLIT_PAIR|TIMER_CFG_B_PWM);
TimerLoadSet(TIMER0_BASE, TIMER_B, ulPeriod);
TimerMatchSet(TIMER0_BASE, TIMER_B, dutyCycleRed);
TimerEnable(TIMER0_BASE, TIMER_B);
GPIOPinConfigure(GPIO_PF1_T0CCP1);
GPIOPinTypeTimer(GPIO_PORTF_BASE, GPIO_PIN_1);
//blue pin setup
SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER1);
TimerConfigure(TIMER1_BASE, TIMER_CFG_SPLIT_PAIR|TIMER_CFG_A_PWM);
TimerLoadSet(TIMER1_BASE, TIMER_A, ulPeriod);
dutyCycleBlue=ulPeriod;
TimerMatchSet(TIMER1_BASE, TIMER_A, dutyCycleBlue);
TimerEnable(TIMER1_BASE, TIMER_A);
GPIOPinConfigure(GPIO_PF2_T1CCP0);
GPIOPinTypeTimer(GPIO_PORTF_BASE, GPIO_PIN_2);
//green pin setup
TimerConfigure(TIMER1_BASE, TIMER_CFG_SPLIT_PAIR|TIMER_CFG_B_PWM);
TimerLoadSet(TIMER1_BASE, TIMER_B, ulPeriod);
TimerMatchSet(TIMER1_BASE, TIMER_B, dutyCycleGreen);
TimerEnable(TIMER1_BASE,TIMER_B);
GPIOPinConfigure(GPIO_PF3_T1CCP1);
GPIOPinTypeTimer(GPIO_PORTF_BASE,GPIO_PIN_3);
while(1){
dutyCycleRed--;
dutyCycleBlue=1000; //attempt to turn off green and blue LEDs
dutyCycleGreen=1000;
TimerMatchSet(TIMER0_BASE,TIMER_B, dutyCycleRed);
//TimerMatchSet(TIMER1_BASE,TIMER_A, dutyCycleBlue);
//TimerMatchSet(TIMER1_BASE,TIMER_B, dutyCycleGreen);
SysCtlDelay(100000);
}
}
Also, when using the HCS08 I got used to reading the datasheet, finding the registers I needed to modify to achieve my desired behaviour, and writing to those memory addresses directly. I quite like this approach because I can follow what's actually going on at a hardware level - the API just feels like an extra layer of abstraction to learn. The datasheet does seem to reference how to set up PWM in this way - page 677-678 have instructions like "Write the GPTM Configuration (GPTMCFG) register with a value of 0x0000.0004". How do you actually achieve this in code composer? The HCS08 used CodeWarrior and if I remember rightly you just had to say
GPTMCFG = 0x0000.0004
but I tried this in CCS and it didn't work.
Any help anyone could give me would be massively appreciated!
