topic Re: Can't get ADC interrupt to work in LPCXpresso IDE

Can't get ADC interrupt to work

lpcware — Wed, 15 Jun 2016 22:41:05 GMT

Content originally posted in LPCWare by g4bch on Mon Jun 14 05:15:25 MST 2010
Has anyone any ideas what I'm not doing that is stopping the A/D converter from working.
I'm trying to get the A/D to trigger from 32 bit counter 0 as it resets on MR0 match. I also want to use a PWM output at the same period with ON/Off ratio set by match register 2.
By monitoring the peripheral registers I can see that the counter and the PIO0, 1 PWM output are active, but not the A/D.
The A/D seems to be set up to start on the rising edge of CT32B0_MAT0, but the program just hangs waiting for interrupt with the A/D register stuck at 0.
The code snip shows the timer and A/D set up.
Any ideas as to what I'm missing?
Peter

Code snip
/******************************************************************/
    //set up counter timer
    // clock already set to 48MHz by CMSIS set up

    //CT32B0 Using Match register 0 to trigger ADC and generate PWM timing
    //Trigger ADC at 250kHz
    LPC_SYSCON->SYSAHBCLKCTRL |= (1<<9); //turn on timer clock
    //set up 32 bit counter timer TMR32B0 as follows:
    //period 250kHz set by match register 0 to allow triggering of A/D
    //PWM output on match 2
    LPC_TMR32B0->MR0 = Period;      //250kHz in Match register 0
    LPC_TMR32B0->MR2 = Period/2;    //set PWM to half scale to start
    LPC_TMR32B0->PWMC = 0x1<<2;     //enable PWM output CT32B0_MAT2
    LPC_TMR32B0->MCR = 0x1<<1;        // Reset on MR0
    LPC_TMR32B0->TCR = 0x1;         //Enable 32 bit timer 0
    //enable PWM output on match 2, copied from timer32.c lines 380/1
    LPC_IOCON->PIO0_1   &= ~0x07;
    LPC_IOCON->PIO0_1   |= 0x02;    // enable Timer0_32 MAT2

/******************************************************************/
    //Set up ADC   copied & modified from adc.c
    //Input on channel 7 triggered from match 0 on 32 bit timer 0
    //read by interrupt
      /* Disable Power down bit to the ADC block. */
      LPC_SYSCON->PDRUNCFG &= ~(0x1<<4);

      /* Enable AHB clock to the ADC. */
      LPC_SYSCON->SYSAHBCLKCTRL |= (1<<13);

      LPC_IOCON->PIO1_11   = 0x01;    // Select AD7 pin function

      //Select AD input 7 for conversion
      LPC_ADC->CR = 0x1<<7;
      //set up ADC clock divider bits 8 - 15
      LPC_ADC->CR |= ((SystemCoreClock/LPC_SYSCON->SYSAHBCLKDIV)/ADC_CLK-1)<<8;
      // BURST = 0, CLKS = 000 10 bit resolution
      //ADC conversion starts on rising edge of CT32B0_MAT0
      LPC_ADC->CR |= (0b0100<<24);

       //enable ADC interrupt
      NVIC_EnableIRQ(ADC_IRQn);
      LPC_ADC->INTEN = 0x1<<7;        /* Enable interrupt for channel 7 */
/**************************************************************************/

Re: Can't get ADC interrupt to work

lpcware — Wed, 15 Jun 2016 22:41:06 GMT

Content originally posted in LPCWare by domen on Mon Jun 14 05:35:20 MST 2010
NVIC_EnableIRQ(TIMER_32_0_IRQn); ?

Re: Can't get ADC interrupt to work

lpcware — Wed, 15 Jun 2016 22:41:06 GMT

Content originally posted in LPCWare by g4bch on Mon Jun 14 09:18:44 MST 2010
I'll give it a try, but I want the interrupt to be generated by the ADC when it has completed conversion after being triggered from the timer. I would expect that enabling the timer interrupt would cause an interrupt when the timer resets as well as the A/D.
Peter

Re: Can't get ADC interrupt to work

lpcware — Wed, 15 Jun 2016 22:41:07 GMT

Content originally posted in LPCWare by Brinkand on Tue Jun 15 07:32:05 MST 2010
Seems to me You are missing the connection between the timer and the ADC, which is not very clear from the manual. I suggest, You add PWM to MR0; this works for me. The problem is that the timer match bit is not directly coupled to the ADC, but via some functionality, which is also used if You pin out the signal. I have succeded using one of three solutions:
- Setting EMC0 in the timer EMR register to 0x3 toggle (You get half ADC rate)
- Setting EMC0 to 0x2 and then reset EM0 from the ISR (Adds overhead)
- Setting PWMC to 0x1. This cheats the timer to believe You want PWM, but the get the rigth waveform at the ADC trigger input.

I include code snippets from my code. Excuse if comments are not all up to date.

void ADCInit( void )
{
  //uint32_t i;

  /* Disable Power down bit to the ADC block. */  
  LPC_SYSCON->PDRUNCFG &= ~(0x1<<4);

  /* Enable AHB clock to the ADC. */
  LPC_SYSCON->SYSAHBCLKCTRL |= (1<<13);

  LPC_IOCON->JTAG_TDO_PIO1_1  &= ~0x9F;    // was 0x8F
  LPC_IOCON->JTAG_TDO_PIO1_1  |= 0x02;  /* ADC IN2 */
  LPC_IOCON->JTAG_nTRST_PIO1_2 &= ~0x9F; // was 0x8F
  LPC_IOCON->JTAG_nTRST_PIO1_2 |= 0x02; /* ADC IN3 */

  LPC_ADC->CR = 0x5200a04;  // Implies CT32B0 MAT1 triggers sampling on rising edge and channel 2 is only channel used. 
  NVIC_EnableIRQ(ADC_IRQn);
  LPC_ADC->INTEN = 0x04;        /* Enable interrupt on channel 2 only. */

  return;
}


// CT32B0 setup. This timer is clocked from CT16B0 MAT1 via external connection to CT32B0_CAP0.
    LPC_SYSCON->SYSAHBCLKCTRL |= (1<<9);
    LPC_IOCON->PIO1_5 &= ~0x07;    /*  Timer0_32 I/O config */
    LPC_IOCON->PIO1_5 |= 0x02;    /* Timer0_32 CAP0 */
    //LPC_IOCON->PIO1_6 &= ~0x07;
    //LPC_IOCON->PIO1_6 |= 0x02;    /* Timer0_32 MAT0 */
    LPC_IOCON->PIO1_7 &= ~0x07;
    LPC_IOCON->PIO1_7 |= 0x02;    /* Timer0_32 MAT1 */
    //LPC_IOCON->PIO0_1 &= ~0x07;
    //LPC_IOCON->PIO0_1 |= 0x02;    /* Timer0_32 MAT2 */
    //LPC_IOCON->JTAG_TDI_PIO0_11 &= ~0x07;
    //LPC_IOCON->JTAG_TDI_PIO0_11 |= 0x03;    /* Timer0_32 MAT3 */
    GPIOSetDir( 1, 5, 0 );  // Set as input for clock
    GPIOSetDir( 1, 7, 1 );  // Set as output - just to measure ADC trigger signal


    LPC_TMR32B0->MCR = 0x0400; /* Reset at MR3*/
    
    LPC_TMR32B0->MR3 = 4; /* Match register 3 - cycle length - divide by 4 */
    
    LPC_TMR32B0->MR1 = 3;          // Turn on at third pulse in sequence of 4 
    LPC_TMR32B0->PWMC = 0x02;             /* PWMC register -MAT1 is PWM. */
    LPC_TMR32B0->CTCR = 0x02;   // Update on falling edge of CAP0.
    LPC_TMR32B0->TCR = 1;

Re: Can't get ADC interrupt to work

lpcware — Wed, 15 Jun 2016 22:41:07 GMT

Content originally posted in LPCWare by g4bch on Tue Jun 15 09:26:34 MST 2010
Thanks for the pointers.
I'll give it a try this evening when I get home. I'm using most of the output pins but I'm sure I can work around losing one to get the ADC working.
Peter

Re: Can't get ADC interrupt to work

lpcware — Wed, 15 Jun 2016 22:41:08 GMT

Content originally posted in LPCWare by Brinkand on Tue Jun 15 23:28:53 MST 2010
You do not need to loose an output pin. I pinned out the trigger signal, as it is nice to track the timing on my oscilloscope. Just leave the IOconfig as it is. According to my investigations, the connection is as shown below:

MRx -> some logic -> MATx register -> IOconfig -> output pin.

My main message is that ADC looks at CTxxBx_MATx, which is not same as MRx. In between is some logic, which must be configured before ADC sees the trigger. And PWM makes the most logical choice here when it comes to functionality, even though the PWM term is unfamiliar for ADCs.

Note that I clock from CAP; You need to switch to main clock to make timer run.

Re: Can't get ADC interrupt to work

lpcware — Wed, 15 Jun 2016 22:41:09 GMT

Content originally posted in LPCWare by g4bch on Tue Jun 15 23:55:02 MST 2010
Thanks for all the help Brinkand
I've got the ADC working now, it was that extra link to the hardware that I was missing and could not see in the handbook.
Thank you
Peter