LPCXpresso IDE中的主题 Re: Inverse PWMs

Inverse PWMs

lpcware — Wed, 15 Jun 2016 21:48:56 GMT

Content originally posted in LPCWare by magnetronus on Thu Aug 27 01:24:35 MST 2015
How can I do 2 inverse PWMs in the same timer?

I mean, for example, I configured CT32B0_MAT1 for counter reset, PWM mode is enabled for CT32B0_MAT0 and CT32B0_MAT3 with 50% duty-cycle (half period of MAT1).
CT32B0_MAT0 and CT32B0_MAT3 have the same waveform.
My question is, how can I get inverse waveform for CT32B0_MAT3 for example (anti-phase)?

Re: Inverse PWMs

lpcware — Wed, 15 Jun 2016 21:48:56 GMT

Content originally posted in LPCWare by R2D2 on Thu Aug 27 01:30:03 MST 2015
What about using interrupts?

Re: Inverse PWMs

lpcware — Wed, 15 Jun 2016 21:48:57 GMT

Content originally posted in LPCWare by magnetronus on Thu Aug 27 02:34:13 MST 2015
When I use interrupt (where I toggle GPIOs) I get undesirable time shift (because PIO1_6/MAT0 and R_PIO0_11/MAT3 use different ports).
See attached screenshot from scope.

Re: Inverse PWMs

lpcware — Wed, 15 Jun 2016 21:48:58 GMT

Content originally posted in LPCWare by R2D2 on Thu Aug 27 02:56:11 MST 2015

Quote: magnetronus
...(because PIO1_6/MAT0 and R_PIO0_11/MAT3 use different ports).

:quest:

Sorry, can't follow you. Could be useful to post a sample (if we are talking about LPCXpresso) to show what you are doing in detail (optimization, inlining...) and which MCU you are using...

Re: Inverse PWMs

lpcware — Wed, 15 Jun 2016 21:48:58 GMT

Content originally posted in LPCWare by magnetronus on Thu Aug 27 03:17:14 MST 2015
O'k.

I use LPCXpresso, my code optimize for size (-Os).
I use LPC1343 MCU.

Timer0 32bit initialization:

/* Enable the clock for CT32B0 */
LPC_SYSCON->SYSAHBCLKCTRL |= (0x01 << 9);

/* Selects function PIO1_6 */
LPC_IOCON->PIO1_6 &= ~0x07;

GPIO_SetDir(GPIO_PORT1, GPIO_BIT6, GPIO_DIR_OUT);
GPIO_SetValue(GPIO_PORT1, GPIO_BIT6, GPIO_LEVEL_LOW);

/* Selects function R_PIO0_11 */
LPC_IOCON->R_PIO0_11 &= ~0x07;
LPC_IOCON->R_PIO0_11 |= 0x01;

GPIO_SetDir(GPIO_PORT0, GPIO_BIT11, GPIO_DIR_OUT);
GPIO_SetValue(GPIO_PORT0, GPIO_BIT11, GPIO_LEVEL_HIGH);

                /* Set period */
                LPC_TMR[CT32B0]->MR[MAT1] = SysTick_GetPeriod(120000);    // 120 KHz
                
/* Set interrupt and reset on CT32B0_MAT1 */
LPC_TMR32B0->MCR = LPC_TIMER_MCR_MR1I | LPC_TIMER_MCR_MR1R;

/* Enable interrupt vector for 32-bit Timer 0 */
NVIC_EnableIRQ(TIMER_32_0_IRQn);

Interrupt (for GPIOs toggle):

if (LPC_TMR32B0->IR & LPC_TIMER_IR_MR1INT)
{
LPC_TMR32B0->IR |= LPC_TIMER_IR_MR1INT;/* clear interrupt flag */

volatile uint8_t math1_6 = GPIO_TestValue(GPIO_PORT1, GPIO_BIT6, GPIO_LEVEL_LOW) ? GPIO_LEVEL_HIGH : GPIO_LEVEL_LOW;
volatile uint8_t math0_11 = GPIO_TestValue(GPIO_PORT0, GPIO_BIT11, GPIO_LEVEL_LOW) ? GPIO_LEVEL_HIGH : GPIO_LEVEL_LOW;

                assert(math1_6 != math0_11);

GPIO_SetValue(GPIO_PORT1, GPIO_BIT6, math1_6);
GPIO_SetValue(GPIO_PORT0, GPIO_BIT11, math0_11);
}

Re: Inverse PWMs

lpcware — Wed, 15 Jun 2016 21:48:59 GMT

Content originally posted in LPCWare by R2D2 on Thu Aug 27 03:23:56 MST 2015
I'm not sure which toolchain and libraries you are using in detail (code snippets are not very informative :(( ), but of course functions like GPIO_TestValue() and GPIO_SetValue() are damned slow and should be replaced...

Re: Inverse PWMs

lpcware — Wed, 15 Jun 2016 21:48:59 GMT

Content originally posted in LPCWare by magnetronus on Thu Aug 27 03:51:22 MST 2015
You right.

Re: Inverse PWMs

lpcware — Wed, 15 Jun 2016 21:49:00 GMT

Content originally posted in LPCWare by R2D2 on Thu Aug 27 04:56:47 MST 2015
Another option (without interrupts) is to use PWM and toggle MATCH outputs via EMR.

Of course you have to preset MATCH outputs high / low (via EMR) before...

Re: Inverse PWMs

lpcware — Wed, 15 Jun 2016 21:49:00 GMT

Content originally posted in LPCWare by lpcxpresso-support on Thu Aug 27 06:11:29 MST 2015
If your part has an SCT (a.k.a. SCTimer) you might look into using that.

There is the Red State tool in LPCXpresso to help configure it and the LPCOpen libraries have an API for some configurations.

Ciao,
LPCXpresso-Support

Re: Inverse PWMs

lpcware — Wed, 15 Jun 2016 21:49:01 GMT

Content originally posted in LPCWare by R2D2 on Thu Aug 27 06:14:10 MST 2015

Quote: lpcxpresso-support
If your part has an SCT (a.k.a. SCTimer) you might look into using that.

LPC1343 :D

Re: Inverse PWMs

lpcware — Wed, 15 Jun 2016 21:49:02 GMT

Content originally posted in LPCWare by R2D2 on Thu Aug 27 07:47:35 MST 2015
And with EMR your delay should disappear:

[img=640x480]https://www.lpcware.com/system/files/F0002TEK.JPG[/img]