Project: create an analog signal using MSP430G2553

Hi,

Seems like you have the right idea.

When the micro starts up though, all general purpose input/output pin directions are set as inputs.  This is the 'safe' way, to prevent them perhaps driving things they shouldn't.  You don't need to set the pins as inputs as your first task.  Although it shouldn't hurt to do so.

Statements like 'x &= ~y' and 'x |= y' modify the current value of x.  If that were a port direction register, it would mean "take the value in the port direction register that it has now, and modify some of the bit values (although some might be all of them depending on what y is)"  If you know how you want the pins set up, you can just assign them with an equals sign:

P1DIR = 0x00;   //all port 1 as inputs, which they are anyway

P2DIR = 0x87;  //port 2 bits 0,1,2 and 7 as outputs - they will initially drive low as P2OUT starts up as 0x00

You haven't mentioned about the DAC - is it a parallel one?  You'll need to connect this to some port pins too.

For the heart of the code, you firstly need to read the DIP switch setting by reading the values on the input pins.

As the MSP is a 16 bit device and ports are only 8 bits wide, you'll have to do this in two chunks to read 12 bits, then stitch them together to get a 12 bit number:

unsigned int temp1, temp2, result;

temp1 = P1IN;   //read the value of the 8 pins on Port 1 into the lowest 8 bits of temp1

temp2 = P2IN;   //read the value of the pins on Port 2 (all of them including the output pins) into lowest bits of temp2

You'll then need to manipulate the bits in temp1 and temp2 to create 'result', which has the bits where you need them.  This will depend on whether the DIP switch Least Significant Bit is connected to Port1 or Port2, and whether it is the lowest number bit used in that port or the highest bit.  Something like:

result = (temp2 & 0x78);   //leave only the bits we are interested in set if they read high.  Zero non-used bits

result = result << 5; // the lowest bit of interest (bit 3) needs to become bit 8, to make room for lowest 8 bits

result = result | temp1;  //any bits in temp1 that read as set now go into the lowest 8 bits of the number.

You now have 'result' holding 12 bits of the DIP switch.  You can do all this in one line as:

result = ((temp2 & 0x78) << 6 ) | temp1;

But make sure you think through the individual actions of each part and use brackets to constrain the order of execution.

You can now start to increment or decrement 'result' and output the values to the DAC.

Hope that helps.

Hey Tony,

I apologise for not replying earlier,

Two days ago I tried your  commands

WDTCTL=WDTPW+WDTHOLD;

P1DIR = 0x00;  

P2DIR = 0x87; 

unsigned int temp1, temp2, result;

result = (temp2 & 0x78); 

result = result << 5;

result = result | temp1; 

//afterwards for decrement & increment

while(result >=0 && result<=4095){

         result++;

}

while(result >=0 && result<=4095){

         result--;

}

I used oscilloscope , but there was NO frequency of my circuit.

I connected the DIP switch - with MSP430g2553 - with the PARALLEL DAC7611p 

Output of that circuit was 3 Volt DC

Although I wanted an analog triangle 0-3 V. 

I believe that there must be some commands on frequency.

Maybe I made some mistakes on increasing/ decreasing the RESULT

What do you say ?

Thanks a lot

 Hi, some analysis necessary:

Antonios Katsikinis said:

1. input 12bit from deep switch ->use them as a StartingNumber

 You mean DIP switch? use program instead, is more simple to control.

Antonios Katsikinis said:

4. that digital signal goes to a DAC7611p , so to output an analog signal

 This appear as a serial SPI like expensive DAC, are you owning it? Otherwise another better  chip or PWM can be used instead.

 Nothing is defined about what are your goal, so resolution and bandwidth of signal, again some part like MSP430F26x carry two 12 bit DAC onboard and chip is costing less than DAC itself.

see there for a dev board

https://www.olimex.com/Products/MSP430/

 or launchpad using MSP430G2553

 If you own the dac a driving routine is needed SPI based or Bit banging to transfer data to DAC.

Thank you,

all of you for replying to my post, 

I own MSP430g2553 and DAC7611p. 

I made some mistakes. DAC7611p is a SERIAL DAC (12 bits- 8 pins) as Tony said.

I 'll leave the DIP switch and use program (a lot easier). So my program will change a little.

Before some years I did use the R2R (ladder), although now I prefer to use the DAC.

I used as input to the pin (SDI - Serial Data Input) of DAC7611p , the output of MSP430.

SO NOW my issue, what is needed, is to program MSP430 to create a signal 

my thinking is to create a digital signal which will move from 0 to 3 V and back (from 3 to 0)

 that will be inserted to the DAC and the result should be an analog signal , between 0 -3 V.

I don' t know about the frequency

also don' t know, while changing the bits from 0000 to 4095 (2^12), if the voltage changes from 0 to 3

thank you

Antonis

Antonios Katsikinis said:

I don' t know about the frequency

also don' t know, while changing the bits from 0000 to 4095 (2^12), if the voltage changes from 0 to 3

 Ok Try a step by step..

 What is the goal of your project so what you think to realize and what you expect to do? This can help us understand better solution.

 Other, Hardware SPI or Bit Bang?

 Bit bang

Use as much as possible predefined constant than number.

 On header BIT0 to BITxx are predefined as 01 02 04 08.... and are more readable than an hex number.

use shift left n bit  <<n  or shift right n bit >>n

 no time constraint never if cpu at full speed than data hold.

Init interface:

 Set CS high

Set Clk High

Set LD High

 Move data:

Set CS low

for (12 times)

       Set clock low

        copy bit 11 of DAC value to data pin

        set CLK High

        Shift Dac value left

Now set CS High

Set LD Low

Set LD High

//********************************* Code BIT BANG ************************************************************

/* enjoy this code and call as OCY show you.. Just customize for pin

 Biggest data or clock setup is 30nS, instruction time @16Mhz is 62.5nS so we don't worry about...

 Customize x, z etc to your port number, bit y k etc to bit number of your port and extend macro to all oher  CLR LD

*/

#define CS_LO (PxOUT&=~BITy)

#define CS_HI (PxOUT|=BITy)

#define SDI_LO (PzOUT&=~BITk)

#define SDI_HI (PzOUT|=BITk)

.........

void send_to_adc(value)

{ int i;

  CS_LO;

  for(i=0;i<12;i++)

  {

     CLK_LO;

     if(data&BIT11) // out MSB first

         SDI_HI;   // data bit is 1

      else

          SDI_LO;  // data bit is 0

      data<<1; // shift  left data

      CLK_HI;

  }

  CS_HI;

}

void load_adc(void)

{

  LD_LO;

  LD_HI;

}

// call this before the other just after setting Watchdog and port direction

void Initadc(void)

{

CS_HI;

 LD_HI;

}

 Hi again, i leave this separate to not overload...

Antonios Katsikinis said:

also don' t know, while changing the bits from 0000 to 4095 (2^12), if the voltage changes from 0 to 3

Inserrt function code before main or use forrward header declaration

init_ADC(); // set adc pin level...

 // this set dac value to 0

    send_to_adc(0);
    load_adc();
// this set dac value to full scale

    send_to_adc(4095); // oxffff set full scale too but limited to 0X0FFF by resolution
    load_adc();

// this set to middle of FS value

    send_to_adc(2047);
    load_adc();

Other value set to

  FS*value/4095

 FS is 2¹²-1 and not 2¹²

unsigned MAxint in general is 2ⁿ-1

if singed MAXINT is 2^n-1-1 accounting the sign bit.
 

I wanted to upload my "plan"

I'm planning NOT to use the DIP switch, as you proposed me.

So everything I need is to 

CREATE AN ANALOG SIGNAL. It would be better if that signal will be triangle.

Roberto, thank you for uploading your thinking.

But I don' t know the differences between bit bang and SPI and I'm a little confused.

And really need to finish this project till Wednesday.

Thanks alot

Antonis

I did whatever you told me

I debugged it on CCS. There' s 1 mistake 

here : if(data&BIT11) // out MSB first

it says -> undefined data and undefined bit11

Antonios Katsikinis said:

it says -> undefined data and undefined bit11

 When is solved please tell us and mark post as verified to give thank for time to your problem.

thank you very much

well, code had no mistake although while debugging, there are 3 errors

I couldn't load our code to msp430

Now I need to study 2 courses.

I will continue with this project after 26 June

I' ll let you know here thanks a lot

Hello

I' m back again to build this project right !!!

The program is "due to" Roberto Romano

#include <msp430.h>

#define CS_LO (P2OUT&=~BIT3)

#define CS_HI (P2OUT|=BIT3)

#define SDI_LO (P2OUT&=~BIT1)

#define SDI_HI (P2OUT|=BIT1)

#define CLK_LO (P2OUT&=~BIT2)

#define CLK_HI (P2OUT|=BIT2)

#define LD_LO (P2OUT&=~BIT0)

#define LD_HI (P2OUT|=BIT0)

void send_to_adc(int value)

{ int i;

CS_LO;

for(i=0;i<12;i++)

{

CLK_LO;

if(value&BITB) // out MSB first

SDI_HI; // data bit is 1

else

SDI_LO; // data bit is 0

value<<1; // shift left data

CLK_HI;

}

CS_HI;

}

void load_adc(void)

{

LD_LO;

LD_HI;

}

// call this before the other just after setting Watchdog and port direction

void Initadc(void)

{

CS_HI;

LD_HI;

}

int main(void)
{
WDTCTL = WDTPW | WDTHOLD; // Stop watchdog timer

P1DIR = 0; //input Port1

P2DIR = BIT0 | BIT1 | BIT2 | BIT3; //input P2.3-P2.6, Out bit 0..3

P1OUT = 0xff; // required by next instruction to pullup/pulldown

P1REN =0xFF; //enable pull-up resistor

P2OUT = 0xff; // required by next instruction to pullup/pulldown and init SPI too

P2REN |= 0xf0;

Initadc(); // set adc pin level

// this set dac value to 0

send_to_adc(0);
load_adc();
// this set dac value to full scale

send_to_adc(4095); // oxffff set full scale too but limited to 0X0FFF by resolution
load_adc();

// this set to middle of FS value

send_to_adc(2047);
load_adc();

}

my plan is this

6786.TELIKO_PLANO.pdf

I run this on Code Composer Studio v5.5 

build -no errors -few warnings

debug -> run ... 

checked the oscillator for frequency, but I only got Voltage ( DC Voltage before my DAC, no freq)

any idea ???

Should I change the "thesis" of any Jumper ?

Should I solve the warnings ?

On my MSP430G2553, my experience is poor. I run the example programs, without a problem, BUT need your help here !

Antonios Katsikinis said:

value<<1; // shift left data

 Antonios, a lot of time elapsed but still you are at same BEGINNER LEVEL!!!!

 YOU MUST LEARN PROGRAMMING BEFORE TO DO SIMPLE THINGS!!!!!!!

 again the warning come from a mistyped line:

Antonios Katsikinis said:

value<<1; // shift left data

this must be

value=value<<1;

or in compact form

value>>=1; edit :  value<<=1;

 Without this data don't load on dac and just bit 11 set all bit. This must output at almost a square wave

 I cannot help you solving your problem, you got too much so PLEASE learn c programming at a decent level otherwise you cannot get nothing and automation require good knowledge of both Mathematics and programming!

You are right

I' m using 3 rectifier diodes IN0001

So no to have voltage over 4.1

Although I Forgot to draw it in my plan !!! 

The problem with rectifier diodes is that their forward voltage depends on current. MSP is low current, so diode voltage drop is low too. Well, as soon as the MSP starts to break down, current will increase and so does the diode voltage, keeping the MSP at the edge between life and death :)