SYSAHBCLKCTRL bit 16 (IOCON) problem - lpcware

PWM for LPC1114 - tombond Fri, 2012-03-16 08:12

http://www.lpcware.com/content/forum/pwm-for-lpc1114

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Hi,

I'm a student from germany and atm I'm doing a little project using the LPC1114/302. Therefore I need a 2730Hz 50% PWM.

Now what I did was:

LPC_SYSCON->SYSAHBCLKCTRL |=  (1<<8);             // Enable Clock for TMR1
LPC_IOCON->PIO1_9 |=  (1<<0);                     // PIN1_9 = CT16B1_MAT0
LPC_TMR16B1->MR0 = 2200;                          // 50% Duty Cycle
LPC_TMR16B1->MR3 = 4400;                          // Cycle Length
LPC_TMR16B1->MCR |= (1<<10);                      // TC Reset on MR3 Match
LPC_TMR16B1->PWMC |= (1<<0);                      // PWM Mode          
LPC_GPIO1->DIR |= (1<<9);                         // Output
LPC_TMR16B1->TCR |= (1<<0);                       // GO

but the Pin1_9 stays 3,3V without any changes.

Even LPC_TMR16B1->EMR &= ~(1<<0); didn't change a thing, it still is high.

Does anybody know what I'm doing wrong?

EDIT: While debugging, I just found out that writing the IOCON->PIO1_9 isn't working. Any ideas?

Thanks,
Thomas


Fri, 2012-03-16 08:46 #1 Ex-Zero

This part of your code is working 

    LPC_SYSCON->SYSAHBCLKCTRL |=  (1<<8);             // Enable Clock for TMR1
    LPC_IOCON->PIO1_9 |=  (1<<0);                     // PIN1_9 = CT16B1_MAT0
    LPC_TMR16B1->MR0 = 2200;                          // 50% Duty Cycle
    LPC_TMR16B1->MR3 = 4400;                          // Cycle Length
    LPC_TMR16B1->MCR |= (1<<10);                      // TC Reset on MR3 Match
    LPC_TMR16B1->PWMC |= (1<<0);                      // PWM Mode
    LPC_TMR16B1->TCR |= (1<<0);                       // GO

and doing exactly what it should: generating 50% 10909 Hz PWM (at 48MHz).

If you don't see PIO1_9 changing, use your debugger to check all registers you've used. Probably you've changed some settings (SystemInit() ?) and now that's surprising you 

Edit: If IOCON isn't working SYSAHBCLKCTRL bit 16 (IOCON) is reset :rolleyes:


Fri, 2012-03-16 09:05 #2 tombond

Thank you very very much!

Enabling the IOCON bit solved the problem, but still I don't get why 

Do I have to set this bit to make changes in IOCON possible?

I never thought of this because in aaaall the threads around here no one ever said anything about enabling this bit xD

Could you please explain to me why I had to do this?

Thanks for your time,

Thomas

Fri, 2012-03-16 09:22 #3 

Do I have to set this bit to make changes in IOCON possible?

Yes 

Usually CMSIS is doing that for you (therefore that's not mentioned in samples) in system_LPC11xx.c:

#define AHBCLKCTRL_Val        0x0001005F

...

LPC_SYSCON->SYSAHBCLKCTRL = AHBCLKCTRL_Val;

If you don't use CMSIS or set AHBCLKCTRL yourself, default value is used and bit 16 is reset 

Fri, 2012-03-16 09:37 #4 tombond

Thanks again for the explanation.

I'm not using CMSIS because I use IBM Rational Rhapsody to create a UML model, the Strauss bridge by Willert and µVision from Keil. 

A professor here at my school gave me a short introduction to all this stuff but I have a really hard time getting into it. 

I copied my system_lpc11xx.c from a Keil demo project called "RTX_Blinky", so I don't know if it's possible to use CMSIS with µVision instead of LPCXpresso.

.END

// ***********************************************************************
// Program     - PWM Blinky
// Description - Blink Somy Board LED PIO0_8 using PWM 
// Build       - 2013.08.08.02
// Date        - 2013aug09hkt1259
// Author      - TL Fong (fongmcu.blogspot.hk, tlfong01hongkong@google.com)
// Hardware    - NXP ARM Cortex M0 LPC1114FBD48/302   
// IDE         - MDK-Lite/uVision 4.71, CoLinkEx 1.1, Flash Magic v7.51 
// References  - 
// 1. UM10398 LPC111x/LPC11Cxx User manual R12 2012sep24
// 2. LPC11xx.h CMSIS Cortex-M0 Core Peripheral Access Layer Header File
//    for NXP LPC11xx/LPC11Cxx V1.10 2010nov24
// Notes       -
// 1. PWM pin configuration 
//      PIO0_8/MISO0/CT16B0_MAT0 = Somy LPC1114 Eval Board P4 Pin 3 
// ***********************************************************************

void testXiaBoardPwmBlinky03()
{
  // Enable System AHB clock for CT16B0 timer (Table 21 bit 7 CT16B0)
  LPC_SYSCON->SYSAHBCLKCTRL |= (1 << 7); // CT16B0 = 1 enables CT16B0

  // Enable System AHB clock for IOCON block (Table 21 bit 16 IOCON)
  LPC_SYSCON->SYSAHBCLKCTRL |= (1 << 16); 

  // Set function of PIO0_8 pin (UM10398 Table 79 bits 2:0 FUNC) 
  LPC_IOCON->PIO0_8 &= ~0x7; // FUNC = 0x2 selects function
  LPC_IOCON->PIO0_8 |=  0x2; //   CT16B0_MAT0 
                
  // Set PWM mode for CT16B0_MAT0,3 (Table 293 bit 0 PWMEN0, bit3 PWMEN3)
  LPC_TMR16B0->PWMC |= 0x9; // PWMENO, PWMEN3 = 1 enables MR0, MR3

  // Set External Match Register (Tables 290, 291)
  LPC_TMR16B0->EMR = (0x3 | 0x1); // bits 4, 5 = 11 toggle, bit 0 = 1 ?
  
  // Resets timer counter on a match (Table 286 bit 10 MR3R)
  LPC_TMR16B0->MCR |= 0x400; // MR3R = 1 resets counter on MR3 match

  // Set prescale 12000 count of AHB clock  = 240 uS (Table 279 TMR16B0PR)
  LPC_TMR16B0->PR = 12000; // (1/(50,000,000/2) x 12000 = 240 uS

  // Set cycle length (Table 279 TMR16B0MR3, Figure 68)
  LPC_TMR16B0->MR3 = 4000; //  240uS x 4000 = 0.96 == 1 second

  // Set duty cycle (Table 279 TMR16B0MR0, Figure 68)
  LPC_TMR16B0->MR0 = 2000; // 240uS x 2000 == 0.5 second (50% duty cycle)

  // Start timer (Table 279 TMR16B0CTCR bit0 CEn)
  LPC_TMR16B0->TCR |= 0x1; // CEn = 1 enables timer 

  while (1)
{
// loop forever
}

}