how to change frequency from 1MHz to 4,8 or 16MHZ?

[mady 0]

Hello.

I have a new problem,if somebody can help me.How can I change the frequency to a msp430g2231 from 1MHz to 4,8 or 16MHz? I want to use 19200 baudrate and I understand that this is the problem...

Thanks.

 

Code example:

/******************************************************************************

* Half Duplex Software UART on the LaunchPad

*

* Description: This code provides a simple Bi-Directional Half Duplex

* Software UART. The timing is dependant on SMCLK, which

* is set to 1MHz. The transmit function is based off of

* the example code provided by TI with the LaunchPad.

* This code was originally created for "NJC's MSP430

* LaunchPad Blog".

*

* Author: Nicholas J. Conn - http://msp430launchpad.com

* Email: webmaster at msp430launchpad.com

* Date: 08-17-10

******************************************************************************/

 

#include "msp430g2231.h"

#include "stdbool.h"

#include "stdint.h"

 

 

#define TXD BIT1 // TXD on P1.1

#define RXD BIT2 // RXD on P1.2

 

#define Bit_time 104 // 9600 Baud, SMCLK=1MHz (1MHz/9600)=104

#define Bit_time_5 52 // Time for half a bit.

 

unsigned char BitCnt; // Bit count, used when transmitting byte

unsigned int TXByte; // Value sent over UART when Transmit() is called

unsigned int RXByte; // Value recieved once hasRecieved is set

 

bool isReceiving; // Status for when the device is receiving

bool hasReceived; // Lets the program know when a byte is received

 

// Function Definitions

void Transmit(uint8_t);

void Enter(void);

 

void main(void)

{

char response[2]={0};

char transmitted=1;

int i=0;

 

 

WDTCTL = WDTPW + WDTHOLD; // Stop WDT

 

BCSCTL1 = CALBC1_1MHZ; // Set range

DCOCTL = CALDCO_1MHZ; // SMCLK = DCO = 1MHz

 

P1SEL |= TXD;

P1DIR |= TXD;

 

P1IES |= RXD; // RXD Hi/lo edge interrupt

P1IFG &= ~RXD; // Clear RXD (flag) before enabling interrupt

P1IE |= RXD; // Enable RXD interrupt

TACCR0 = 30; // Delay to allow Ref to settle

TACCTL0 |= CCIE; // Compare-mode interrupt.

TACTL = TASSEL_2 | MC_1;

isReceiving = false; // Set initial values

hasReceived = false;

 

__bis_SR_register(GIE); // interrupts enabled\

 

while(1)

{

if (transmitted)

{

//Transmit(response[0]); //transmit AT command and wait for OK response

//Transmit('a');

// Transmit('T');

// Transmit('I');

// Transmit('1');

/*

Transmit('D'); //call to number, it works good(is just for to send to phone)

Transmit('+');

Transmit('4');

Transmit('2');

Transmit('1');

Transmit('9');

Transmit('0');

Transmit('4');

Transmit('8');

Transmit('6');

Transmit('7');

Transmit('1');

Transmit('9');

Transmit('4');

Transmit(';');

Transmit(0x0D);*/

Enter();

 

transmitted=0;

// __bis_SR_register(CPUOFF + GIE);

}

 

if (hasReceived) // If the device has recieved a value

{

hasReceived = false; // Clear the flag

response=RXByte+1;

//i++;

__bis_SR_register(CPUOFF + GIE);

transmitted=1;

//i=0;

 

Transmit(RXByte+1);

}

//if (~hasReceived) // Loop again if another value has been received

// __bis_SR_register(CPUOFF + GIE);

// LPM0, the ADC interrupt will wake the processor up. This is so that it does not

// endlessly loop when no value has been Received.

}

}

 

void Enter()

{

Transmit(0x0A);

Transmit(0x0D);

}

 

// Function Transmits Character c

void Transmit(uint8_t c)

{

TXByte=c;

while(isReceiving); // Wait for RX completion

CCTL0 = OUT; // TXD Idle as Mark

TACTL = TASSEL_2 + MC_2; // SMCLK, continuous mode

 

BitCnt = 0xA; // Load Bit counter, 8 bits + ST/SP

CCR0 = TAR; // Initialize compare register

 

CCR0 += Bit_time; // Set time till first bit

TXByte |= 0x100; // Add stop bit to TXByte (which is logical 1)

TXByte = TXByte << 1; // Add start bit (which is logical 0)

 

CCTL0 = CCIS0 + OUTMOD0 + CCIE; // Set signal, intial value, enable interrupts

while ( CCTL0 & CCIE ); // Wait for previous TX completion

}

 

// Port 1 interrupt service routine

#pragma vector=PORT1_VECTOR

__interrupt void Port_1(void)

{

isReceiving = true;

 

P1IE &= ~RXD; // Disable RXD interrupt

P1IFG &= ~RXD; // Clear RXD IFG (interrupt flag)

 

TACTL = TASSEL_2 + MC_2; // SMCLK, continuous mode

CCR0 = TAR; // Initialize compare register

CCR0 += Bit_time_5; // Set time till first bit

CCTL0 = OUTMOD1 + CCIE; // Dissable TX and enable interrupts

 

RXByte = 0; // Initialize RXByte

BitCnt = 0x9; // Load Bit counter, 8 bits + ST

}

 

// Timer A0 interrupt service routine

#pragma vector=TIMERA0_VECTOR

__interrupt void Timer_A (void)

{

if(!isReceiving)

{

CCR0 += Bit_time; // Add Offset to CCR0

if ( BitCnt == 0) // If all bits TXed

{

TACTL = TASSEL_2; // SLK, timer off (for power consumption)

CCTL0 &= ~ CCIE ; // Disable interrupt

}

else

{

CCTL0 |= OUTMOD2; // Set TX bit to 0

if (TXByte & 0x01)

CCTL0 &= ~ OUTMOD2; // If it should be 1, set it to 1

TXByte = TXByte >> 1;

BitCnt --;

}

}

else

{

CCR0 += Bit_time; // Add Offset to CCR0

if ( BitCnt == 0)

{

TACTL = TASSEL_2; // SMCLK, timer off (for power consumption)

CCTL0 &= ~ CCIE ; // Disable interrupt

 

isReceiving = false;

 

P1IFG &= ~RXD; // clear RXD IFG (interrupt flag)

P1IE |= RXD; // enabled RXD interrupt

 

if ( (RXByte & 0x201) == 0x200) // Validate the start and stop bits are correct

{

RXByte = RXByte >> 1; // Remove start bit

RXByte &= 0xFF; // Remove stop bit

hasReceived = true;

}

__bic_SR_register_on_exit(CPUOFF); // Enable CPU so the main while loop continues

}

else

{

if ( (P1IN & RXD) == RXD) // If bit is set?

RXByte |= 0x400; // Set the value in the RXByte

RXByte = RXByte >> 1; // Shift the bits down

BitCnt --;

}

}

}

[P!-Ro 4]

First you need to buy that 4 or 8 or 16mhz crystal, because the msp doesn't have one built in. Have you done this yet?

[mady 0]

I have a 12 MHz crystal.

[mady 0]

I can work with 12 MHz if it can be made....

[nobody 47]

1) You do not need a 12MHz crystal. Use 32kHz crystal added to your Launchpad.

 

2) Is it possible that you do not need a crystal at all. You have two options:

- Calibrate your msp430g2231 (instructions is issued here in the forum)

- Use of uncalibrated frequency and manually adjust and change BCSCTL1 and/or DCOCTL.

 

In any case, I suggest you read slau144h.pdf Chapter 5 (pages 273-287).

[none 7]

Beware, AFAIK the Launchpad only supports 9600 baud.

[zeke 693]

Hey Guys,

 

Take a look at this thread for all the nitty gritty details on how to setup the DCO constants.

 

These parts can run at 16MHz no problem.

These parts can also do better than 9600 baud.