CC2538 -- PWM Generator

Michael Dupont

Prodigy 50 points

Other Parts Discussed in Thread: CC2538

Greetings,

Trying to configure one of the GP Timers on CC2538 to function as a PWM Generator. So far, absolutely no success.

Tried to configure as follows:

Timer 0, Section A

Mapped to I/O port A, Pin 0

Port A Pin 0 mapped to Input Capture 1

Nothing real fancy here.

Here is the test code (derived from TI Example Project GPTimer -- periodic_prescaler_16bit

found in the cc2538_foundation_firmware_1_0_1_0 driverlib stuff) :

====================================================================

int

main(void)

{

int delayIndex;

unsigned int pwmDutyCycle = 0x0000;

// Initialize the interrupt counter.

g_ui32Counter = 0;

// Set the clocking to run directly from the external crystal/oscillator.

// (no ext 32k osc, no internal osc)

SysCtrlClockSet(false, false, SYS_CTRL_SYSDIV_32MHZ);

// Set IO clock to the same as system clock

SysCtrlIOClockSet(SYS_CTRL_SYSDIV_32MHZ);

// The Timer0 peripheral must be enabled for use.

SysCtrlPeripheralEnable(SYS_CTRL_PERIPH_GPT0);

// Set up the serial console to use for displaying messages. This is

// just for this example program and is not needed for Timer operation.

InitConsole();

// Display the example setup on the console.

UARTprintf("16-Bit Timer PWM ->");

UARTprintf("\n Timer = Timer0B");

UARTprintf("\n Mode = PWM with variable duty cycle");

// Configure GPTimer0A as a 16-bit PWM Timer.

TimerConfigure(GPTIMER0_BASE, GPTIMER_CFG_SPLIT_PAIR |

GPTIMER_CFG_A_PWM | GPTIMER_CFG_B_PWM);

// Set the GPTimer0B load value to 1sec by setting the timer load value

// to SYSCLOCK / 255. This is determined by:

// Prescaled clock = 16Mhz / 255

// Cycles to wait = 1sec * Prescaled clock

TimerLoadSet(GPTIMER0_BASE, GPTIMER_A, SysCtrlClockGet() / 4000);

TimerControlLevel(GPTIMER0_BASE, GPTIMER_A, false);

// Configure GPIOPortA.0 as the Timer0_InputCapturePin.1

IOCPinConfigPeriphOutput(GPIO_A_BASE, GPIO_PIN_0, IOC_MUX_OUT_SEL_GPT0_ICP1);

// Tell timer to use GPIOPortA.0

// Does Direction Selection and PAD Selection

GPIOPinTypeTimer(GPIO_A_BASE, GPIO_PIN_0);

// Enable processor interrupts.

IntMasterEnable();

// Enable GPTimer0B.

TimerEnable(GPTIMER0_BASE, GPTIMER_A);

UARTprintf("\n");

// Loop forever while the Timer0B runs.

while(1)

{

for (delayIndex = 0; delayIndex < 100000; delayIndex++);

pwmDutyCycle += 0x0F;

pwmDutyCycle &= 0xFFFF;

TimerMatchSet(GPTIMER0_BASE, GPTIMER_A, pwmDutyCycle);

UARTprintf("PWM DC Value: %04X -- %04X -- %04X\r",

pwmDutyCycle,

TimerValueGet(GPTIMER0_BASE, GPTIMER_A),

TimerMatchGet(GPTIMER0_BASE, GPTIMER_A) );

}

====================================================================

Thanks in advance.

mDupont

over 12 years ago

0 Michael Dupont over 12 years ago

Prodigy 50 points

Ok, I solved this.

The issue is that the function, void GPIOPinTypeTimer(uint32_t ui32Port, uint8_t ui8Pins) in gpio.c sets the output that I'm trying to drive to DISABLED (IOC_OVERRIDE_DIS). To enable the output, I used IOC_OVERRIDE_OE instead. Voila. It works.

Cheers,

M.Dupont

0 Michael Dupont over 12 years ago in reply to Michael Dupont

Prodigy 50 points

Further disclosure for anyone who wants to use the example code above:

Use PORTC.0 instead of PORTA.0 as the output. This will map to LED-1 on the SmartRF06 board.

M.Dupont

0 Pe Lopez over 11 years ago in reply to Michael Dupont

Expert 1040 points

Hi,

I have a problema when i define the prescale diferent from 0 ... " TimerPrescaleSet(GPTIMER0_BASE, GPTIMER_A, 4); "

Because the DutyCycle time isn't it proprotional.

Why? anyone can help?

0 Pe Lopez over 11 years ago in reply to Pe Lopez

Expert 1040 points

please... anyone can help...

0 Giuseppe Giancola over 10 years ago in reply to Pe Lopez

Prodigy 40 points

hi, i'm trying to make the pwm work, i've followed the topic, changed the port A.0 to C.0 and used IOC_OVERRIDE_OE in void GPIOPinTypeTimer(uint32_t ui32Port, uint8_t ui8Pins) in gpio.c, but i have no led1 effects, how should i change the interrupt handler to make it work?

thanks in advance

0 Paul White95 over 10 years ago in reply to Michael Dupont

Prodigy 120 points

Instead of modifying gpio.c, just add

IOCPadConfigSet(GPIO_C_BASE, GPIO_PIN_0, IOC_OVERRIDE_OE);

after call to GPIOPinTypeTimer

0 PB_21 over 10 years ago

Intellectual 370 points

HI, I have been using the same code to generate a PWM signal with the changes made accordingly , yet I am not able to generate a 38 khz signal. ( I have removed all the Serial Console messages to be displayed) .

#include <stdbool.h>
#include <stdint.h>
#include <hw_ints.h>
#include <hw_memmap.h>
#include <gpio.h>
#include <ioc.h>
#include <hw_ioc.h>
#include <sys_ctrl.h>
#include <gptimer.h>

int
main(void)
{

int delayIndex;

unsigned int pwmDutyCycle = 0x0000;

SysCtrlClockSet(false, false, SYS_CTRL_SYSDIV_32MHZ);

SysCtrlIOClockSet(SYS_CTRL_SYSDIV_32MHZ);

SysCtrlPeripheralEnable(SYS_CTRL_PERIPH_GPT0);
TimerConfigure(GPTIMER0_BASE, GPTIMER_CFG_SPLIT_PAIR | GPTIMER_CFG_A_PWM | GPTIMER_CFG_B_PWM );
TimerLoadSet(GPTIMER0_BASE, GPTIMER_A, SysCtrlClockGet() / 38000);
TimerControlLevel(GPTIMER0_BASE, GPTIMER_A, false);
IOCPinConfigPeriphOutput(GPIO_C_BASE, GPIO_PIN_0,IOC_MUX_OUT_SEL_GPT0_ICP1);

GPIOPinTypeTimer(GPIO_A_BASE, GPIO_PIN_0);

IOCPadConfigSet(GPIO_A_BASE, GPIO_PIN_0, IOC_OVERRIDE_OE);

GPIOPinTypeGPIOOutput(GPIO_A_BASE, GPIO_PIN_0);

IntMasterEnable();
TimerEnable(GPTIMER0_BASE, GPTIMER_A);

while(1)

{

for (delayIndex = 0; delayIndex < 100000; delayIndex++);

{
pwmDutyCycle += 0x0F;

pwmDutyCycle &= 0xFFFF;

TimerMatchSet(GPTIMER0_BASE, GPTIMER_A, pwmDutyCycle);

}

}

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CC2538 -- PWM Generator