TMP275 - when reading TLow, or THigh, second byte is always FF

Hello

I am attempting to read/write to a TMP275 using an MSP430G2553 (Launch Pad), using the IAR compiler.

The TMP275 has 8K pullups to Vcc on SDA and CLK, stealing power from the Launch Pad.

The TMP275 address pins are tied to Vcc.

I can write and read the control register just fine...

When writing, then reading either TLow or THigh, the 1st byte works as expected, but the second byte always returns 0xFF.

I am aware the G2553 has IC2 capabilities, but I want to use/save the uart for a comm link so I am bit banging the IC2 to run the TMP275

IAR Code:

    WriteTMP275IntToPointer( TMP275_7, TLOW_REG, 0x1230  );

    Temp2 =  ReadTMP275IntAtPointer(TMP275_7);

I have photos of my Oscope writting/reading the data, but at 25MB, zipped, it was to large to include here.

(I can email them individually to you, if you wish)

See the bottom of this file for the definitions of constants.

Thank you.

Where:

void WriteTMP275IntToPointer( unsigned char who, unsigned char DaPointer, unsigned int the_int )
{
    long longint = (((the_int & 0xFF00) << 2 ) | ((the_int & 0x00F0) << 1));
 
    MasterStart();
    
    // write address, writing to pointer
    for(unsigned char position = 0x80; position != 0; position = position >> 1 )    //A
    {
       if( 0 == ((who + WRITE) & position) )
       {
           SetSDALow
       }
       else
       {
           SetSDAHigh    
       }
       Wait100US();  
       SetSCLHigh  
       Wait100US();
       SetSCLLow  
       Wait100US();
    }
    SetSDALow
    Wait100US();
    SetSCLHigh  
    Wait100US();
    SetSCLLow  
    Wait100US();
    // Ack from TMP275 should show up here...

    // set the pointer to config
    for(unsigned char position = 0x80; position != 0; position = position >> 1 )    //B
    {
       if((DaPointer & position) == 0)
       {
           SetSDALow
       }
       else
       {
           SetSDAHigh    
       }
       Wait100US();  
       SetSCLHigh  
       Wait100US();
       SetSCLLow  
       Wait100US();
    }
    SetSDALow
    Wait100US();
    SetSCLHigh  
    Wait100US();
    SetSCLLow  
    Wait100US();
    Wait100US();
    Wait100US();
    // Ack from TMP275 should show up here...

    // send the std config data via pointer
    for(long position = 0x20000; position != 0x0000; position = position >> 1 )    //C
    {
       if(longint & position)
       {
           SetSDAHigh
       }
       else
       {
           SetSDALow    
       }
       Wait100US();  
       SetSCLHigh  
       Wait100US();
       SetSCLLow  
       Wait100US();
    }
    SetSDALow
    Wait100US();
    
    
    MasterStop();

    
    
    Wait100US();
}

unsigned int ReadTMP275IntAtPointer(unsigned char who )
{
    MasterStart();


    for(unsigned char position = 0x80; position != 0; position = position >> 1 )  //F
    {
       if( 0 == ((who + READ) & position) )
       {
           SetSDALow
       }
       else
       {
           SetSDAHigh    
       }
       Wait100US();  
       SetSCLHigh  
       Wait100US();
       SetSCLLow  
       Wait100US();
    }
    SetSDALow
    Wait100US();
    SetSCLHigh  
    Wait100US();
    SetSCLLow  
    Wait100US();
    Wait100US();
    Wait100US();

    
    // Ack from TMP275 should show up here...
    
   unsigned int ReturnValue = 0;
    
 
   SetSDADirectionInput
     
   for(unsigned char Counter = 0x80; Counter != 0; Counter = Counter >> 1)   //G
   {
       SetSCLHigh
       Wait100US();
       if(ReadSDA != 0)
       {
           ReturnValue |= (Counter << 8);
       }
       SetSCLLow;
       Wait100US();
   }
    SetSCLHigh
    Wait100US();
    SetSCLLow  
    Wait100US();

   for(unsigned char Counter = 0x80; Counter != 0; Counter = Counter >> 1)   //G
   {
       SetSCLHigh
       Wait100US();
       if(ReadSDA != 0)
       {
           ReturnValue |= Counter;
       }
       SetSCLLow;
       Wait100US();
   }
    SetSCLHigh
    Wait100US();
    SetSCLLow  
    Wait100US();
    SetSDALow
    Wait100US();

    SetSDADirectionOutput
    MasterStop();
    
    return ReturnValue;
}

void MasterStart( void )
{
    SetSCLHigh  
    SetSDAHigh
    Wait100US();  
    SetSDALow
    Wait100US();  
    SetSCLLow  
    Wait100US();    
}

void MasterStop (void )
{
   SetSCLHigh  
   Wait100US();
   SetSDAHigh
   Wait100US();  
}

//  WHO
#define TMP275_0   0x90
#define TMP275_1   0x92
#define TMP275_2   0x94
#define TMP275_3   0x96
#define TMP275_4   0x98
#define TMP275_5   0x9A
#define TMP275_6   0x9C
#define TMP275_7   0x9E

#define READ  1
#define WRITE 0

// Registers
#define TEMP_REG    0
#define CONFIG_REG  1
#define TLOW_REG    2
#define THIGH_REG   3

// Configuration
#define SHUTDOWN_OFF          0x00   // Enables TMP275
#define SHUTDOWN_ON           0x01   // Shuts down TMP275
#define COMPARE_MODE_0        0x00   // changes state on every excursion
#define COMPARE_MODE_1        0x02   // generates a new interrupt on each excursion
#define POLARITY_ACTIVE_LOW   0x00   // alert is active low
#define POLARITY_ACTIVE_HIGH  0x04   // alert is active high
#define FAULT_QUEUE_1         0x00   // number of excursions before tripping alert = 1
#define FAULT_QUEUE_2         0x08   // number of excursions before tripping alert = 2
#define FAULT_QUEUE_4         0x10   // number of excursions before tripping alert = 4
#define FAULT_QUEUE_6         0x18   // number of excursions before tripping alert = 6
#define RESOLUTION_DOT5C      0x00   // Resolution = 0.5    degrees C or  9 bits
#define RESOLUTION_DOT25C     0x20   // Resolution = 0.25   degrees C or 10 bits
#define RESOLUTION_DOT125C    0x40   // Resolution = 0.125  degrees C or 11 bits
#define RESOLUTION_DOT0625C   0x60   // Resolution = 0.0625 degrees C or 12 bits

#define STD_CONFIG RESOLUTION_DOT0625C + FAULT_QUEUE_1 + POLARITY_ACTIVE_HIGH + COMPARE_MODE_0 + SHUTDOWN_OFF


#define SCL        BIT3
#define SDA        BIT4
#define Temp       0
#define Config     1
#define TLow       2
#define THigh      3
#define ReadSDA    (P2IN & SDA)
#define SetSDAHigh (P2OUT |=  SDA);
#define SetSDALow  (P2OUT &= ~SDA);
#define SetSCLHigh (P2OUT |=  SCL);
#define SetSCLLow  (P2OUT &= ~SCL);
#define SetSDADirectionOutput (P2DIR |=  SDA);
#define SetSDADirectionInput  (P2DIR &= ~SDA);
#define SetSDAPullUp   (P2REN |=  SDA);
#define ResetSDAPullUp (P2REN &= ~SDA);