MSP430G2231: MSP430 and Zero Crossing Detector

Hi James, I´m really impressed with MSP430 and the rich technical material available. Thanks a lot!

I explore extensively TI material, to study, and I found at Air conditioner Indoor Unit a subsystem module that has a Zero Crossing Detector in a Motor Driver. As you can see PIC bellow:

But I cant find a specific code, in Air Conditioner Indoor Unit Reference Design, with the Zero Crossing Detector code to study. Would you can help me to find a .c file that has the ZCD code part?

www.ti.com/.../ductless_aircon_indoor_system

Hi Guys, I'm working on configuring my device to implement a ZCD.

I already understood how to configure comparator_A and interrupt, but at this moment I have a basic doubt: How to configure in the MSP430G2211 with 16Mhz clock. 

I saw in the datasheet on DCO settings frequency (15, 3) that represent 15,25 MHz and I didn't find available lib that has 16MHZ frequency, as we have for 1 MHz ( BCSCTL1 = CALBC1_1MHZ);

- Is possible to reach 16MHz in the MSP430G2211?

- some body can help with a code example, how can I configure it using BCSCTL1 and DCOCTL special registers?

Best Regards,

Alex

HI Bruce, how are you.

I still working in my dimmer device, I already have success to:

> setup clock (16MHz),

> To building a ZCD circuit, using a LVTT (3,3V)

> To building a PWM mechanism to trigger TRIAC

But I working define a comparator_a for prepare a delay stage necessary for start a sincronysm between sin wave and PWM square wave. 

But I have a problem to with comparator_A, I defined: external signal (P1.1) CARSEL, internal reference as 0,5VCC CAREF_2 and interrupt.CAIE. I using on P1.1 (P2CA4)  to tests, +VCC or GND and always the interrupt is reached (P1.0 LED toggled).

Can you help to fix it?

#include <msp430g2452.h>


void main(void)
{
// Comaparator A settings - Set P1.0 if P1.1 > 0.5*Vcc
WDTCTL = WDTPW +WDTHOLD; // Stop WDT
CACTL1 = CAON +CARSEL +CAREF_2; // CAON = Enable comp , CAREF_2 = 0.5*Vcc, CARSEL1 => CAREF_2= -comp, on
CACTL2 = P2CA4; // P1.1/CA1 = +comp
CACTL2 |= CAF; // enable output filter
P1DIR |= 0x01; // P1.0 output, necessary to define P1OUT
// setup interrupts
CACTL1 |= CAIE; // Setup interrupt for Comparator
_BIS_SR(LPM3_bits + GIE); // Enter LPM3, interrupts enabled
}

// Comp_A interrupt service routine -- toggles LED
#pragma vector=COMPARATORA_VECTOR
__interrupt void Comp_A_ISR (void)
{
//CACTL1 ^= CAIES; // Toggles interrupt edge borda de subida ou descida.
//CACTL1 |= CAIES; // Set up for falling (descendente) edge
CACTL1 &= ~CAIES; // Set up for rising (ascendente) edge
CACTL1 &= ~CAIFG; // Clear Interrupt flag
//__delay_cycles(200000);
P1OUT ^= 0x01; // Toggle P1.0
}

Hi James, thanks a lot for your assistance.

I using digital input signal (5v or 0v) to test before my comparator A code, and after it working I planing to connect in the same PIN my ZCD output PIN,  But as I said I didn´t have a success!

My ZCD circuit, It is similar that what I included in the first post here, but i made some adjust to work with 3,3V.

I have planning to use follow algorithm to synchronize PWM Signal w/ sine wave form signal:

 > timer is set up but disabled

> Zero crossing detected on pin

> timer starts counting from zero

> comparator set to "delay to on" value

> counter reaches comparator value

> comparator turns on TRIAC gate

...etc....

If you have another way to synchronize PWM signal w/ sine wave form signal, without use Comparator A,  please would you can share it w/ me?

BR,
Alex

Hi James, thanks a lot for your assistance. 

I got success, as you advise me, to implement ZCD detection using only Interrupts (Port P1 Vector) and a specific electronic circuit. I working right now to adjust the clock and delay to the TRIAC gets turned off inside of the period of ½ wave.

But right now it is my problem, I using MSP430G2452 and SMCLK clock method to ran MSP430 with 16Mhz. But I have some inconsistency when setting it together timer A used also to generate PWM wave signal. As you can see bellow the SMCLK mode uses the same registers (used to form PWM wave) TA0CTL and others.

I need to change my MSP430G2452 to other MSP430 that has DCO inside with 16Mhz,l like MSP430G2553, or I can change capture mode and related registers to another channels like TA0CCTL2?

 // clock settings to form PWM wave

TA0CCR0 = 1000; //The timer counts up to this.
TA0CCTL1 = OUTMOD_7;
TA0CCR1 = 0; //The PWM period, which is 0 uS.
TA0CTL = TASSEL_2 + MC_1;

/* Configure the clock module - MCLK = 1MHz */

for (i = 0; i < 0xfffe; i++); // Delay for XTAL stabilization
j = 0; // Reset pointer

Set_DCO(DELTA_16MHZ); // Set DCO and obtain constants
CAL_DATA[j++] = DCOCTL;
CAL_DATA[j++] = BCSCTL1;

Flash_ptrA = (char *)0x10C0; // Point to beginning of seg A
FCTL2 = FWKEY + FSSEL0 + FN1; // MCLK/3 for Flash Timing Generator
FCTL1 = FWKEY + ERASE; // Set Erase bit
FCTL3 = FWKEY + LOCKA; // Clear LOCK & LOCKA bits
*Flash_ptrA = 0x00; // Dummy write to erase Flash seg A
FCTL1 = FWKEY + WRT; // Set WRT bit for write operation
Flash_ptrA = (char *)0x10F8; // Point to beginning of cal consts
for (j = 0; j < 8; j++)
*Flash_ptrA++ = CAL_DATA[j]; // re-flash DCO calibration data
FCTL1 = FWKEY; // Clear WRT bit
FCTL3 = FWKEY + LOCKA + LOCK; // Set LOCK & LOCKA bit

void Set_DCO(unsigned int Delta) // Set DCO to selected frequency
{
unsigned int Compare, Oldcapture = 0;

BCSCTL1 |= DIVA_3; // ACLK = LFXT1CLK/8
TACCTL0 = CM_1 + CCIS_1 + CAP; // CAP, ACLK
TACTL = TASSEL_2 + MC_2 + TACLR; // SMCLK, cont-mode, clear

while (1)
{
while (!(CCIFG & TACCTL0)); // Wait until capture occured
TACCTL0 &= ~CCIFG; // Capture occured, clear flag
Compare = TACCR0; // Get current captured SMCLK
Compare = Compare - Oldcapture; // SMCLK difference
Oldcapture = TACCR0; // Save current captured SMCLK

if (Delta == Compare)
break; // If equal, leave "while(1)"
else if (Delta < Compare)
{
DCOCTL--; // DCO is too fast, slow it down
if (DCOCTL == 0xFF) // Did DCO roll under?
if (BCSCTL1 & 0x0f)
BCSCTL1--; // Select lower RSEL
}
else
{
DCOCTL++; // DCO is too slow, speed it up
if (DCOCTL == 0x00) // Did DCO roll over?
if ((BCSCTL1 & 0x0f) != 0x0f)
BCSCTL1++; // Sel higher RSEL
}
}
TACCTL0 = 0; // Stop TACCR0
TACTL = 0; // Stop Timer_A
BCSCTL1 &= ~DIVA_3; // ACLK = LFXT1CLK
}

alexander argollo said:

I got success, as you advise me, to implement ZCD detection using only Interrupts (Port P1 Vector) and a specific electronic circuit. I working right now to adjust the clock and delay to the TRIAC gets turned off inside of the period of ½ wave.

Great! Looking at your code, I would not adjust your DCO frequency on the fly. Instead, I would highly recommend fixing the DCO frequency and using a timer to adjust how long the TRIAC gets turned on/off inside the input period from the ZCD. This approach should be much easier and more stable.

I'm happy to see you've got the port interrupts working to detect the ZCD detection - nice work! Now, let's assume that you want the output signal to the TRIAC to equal exactly half the ZCD period. Using your port interrupts, you could start by configuring the port interrupt to fire on rising edge. Then, when this happens, turn on the TRIAC. In your code immediately after this, you'd reconfigure the port interrupts to fire on falling edge. Then, when that interrupt fires, you'd turn off the TRIAC.

Assuming you'd like the pulse-width to be less than half the input ZCD period, then you'd want to use a timer. After configuring the port interrupt to fire on rising interrupts from the ZCD input, start the timer when the interrupt fires and turn on the TRIAC. Then, when the timer interrupt fires after a certain delay, turn off the TRIAC output. Then, start over waiting for the next rising edge input.

Does this make sense? Maybe I'm missing something. See the figure below illustrating what I've described. Again, I would recommend using a fixed DCO frequency.

alexander argollo said:

I need to change my MSP430G2452 to other MSP430 that has DCO inside with 16Mhz,l like MSP430G2553, or I can change capture mode and related registers to another channels like TA0CCTL2?

If you're at a point in your design where you can change your MCU, I'd highly recommend switching from G2xx to our newer FRAM devices. Specifically, the similar MSP430FR2311, which is also 16MHz and has two Timer modules. If this device isn't the best for your application, there's a nice comparison table in Table 1 in the Migrating From the MSP430F2xx and MSP430G2xx Families to the MSP430FR4xx and MSP430FR2xx Family app note.

Fundamentally, your approach won't change but there will be small changes described in this app note. As discussed in Section 3.1, some FRAM advantages include that it's inherently non-volatile memory (so it retains its content even during a power loss), doesn't require an erase before a write, and has far greater write endurance.

Regards,

James