TMP102 Configuration Register Read/Write fail

[rasem]

I need help to setup TMP102 alarm function. My board is NUCLEO-F439ZI

Reading the temperature is working fine.

uint8_t TMP102_ADDR = 0x48 << 1;

uint8_t REG_TEMP = 0x00;

uint8_t buf[12];

buf[0] = REG_TEMP;

ret = HAL_I2C_Master_Transmit(&hi2c2, 0x90, buf, 1, 10);    // OK

ret = HAL_I2C_Master_Transmit(&hi2c2, 0x90, 0x00, 1, 10);   //OK

ret = HAL_I2C_Master_Receive(&hi2c2, 0x90, buf, 2 , 10);    //OK

reads the temperature correctly. Buf[0] and buf[1]has correct temperature data.

I am trying to setup the alarm function. Reading/writing the Limit registers are failing.

Datasheet states that Thigh=80C, and Tlow=70C. After Reset.

I am reading the Thigh registers, with the following code:

uint8_t reghi = 0x03;

ret = HAL_I2C_Master_Transmit(&hi2c2, TMP102_ADDR, reghi, 1, 10); // fail

is sending 0x00 on reghi. I verified by scope.

ret = HAL_I2C_Master_Transmit(&hi2c2, TMP102_ADDR, 0x03, 1, 10);  //fail     

it is sending 0x00 to configuration register.

The only way to send the right value accomplished by:

Unit8_t reghi = 0x03;

buf[0] = reghigh;

ret = HAL_I2C_Master_Transmit(&hi2c2, TMP102_ADDR, buf, 1, 10); OK.

Sending 0x03 to select the Thigh register. Verified by scope.

Now I want to read the value of Thigh.

ret = HAL_I2C_Master_Receive(&hi2c2, TMP102_ADDR, buf, 2 , 100);

The value in buf[0] = 0x00;

The value in buf{1] = 0x00;

I verified it in Debug mode.

The same problem when I write two bytes to Thigh and read it back

It gives 0x00 for both bytes.

If anybody tried to set the alarm successfully in TMp102, please help.

Thanks,

Rasem

[Tesla DeLorean]

Yeah, because it want a POINTER, the address of variable, and not the number/constant itself..

uint8_t reghi = 0x03;

ret = HAL_I2C_Master_Transmit(&hi2c2, TMP102_ADDR, reghi, 1, 10); // fail

is sending 0x00 on reghi. I verified by scope.

ret = HAL_I2C_Master_Transmit(&hi2c2, TMP102_ADDR, 0x03, 1, 10);  //fail     

it is sending 0x00 to configuration register.

The only way to send the right value accomplished by:

uint8_t reghi = 0x03;
ret = HAL_I2C_Master_Transmit(&hi2c2, TMP102_ADDR, (void *)&reghi, 1, 10); // pass via pointer

[rasem]

Hi Tesla DeLorean,

Thank you very much for your quick reply. It was great. I am able to read the High Temperature setting of

80C correctly.

I still need your help setting my own limits:

The following did not work.

uint8_t reghi = 0x03;

uint8_t  temphi[2];

uint8_t lowlimit [2];

temphi[0] = 0x1A;

temphi[1] = 0x00; // set high temp alarm at 26C.

ret = HAL_I2C_Master_Transmit(&hi2c2, TMP102_ADDR, (void *)&reghi, 1, 10); //OK

ret = HAL_I2C_Master_Transmit(&hi2c2, TMP102_ADDR, (void*)&temphi,2, 100);

ret = HAL_I2C_Master_Receive(&hi2c2, TMP102_ADDR, lowlimit, 2 , 100);

// reads lowlimit[0]=0x00, lowlimit[1]=0x00

Coffee on it's way.Thanks.

Rasem

[padawan · Accepted solution]

Hi Rasem

try this:

change 

temphi[0] = 0x1A;

temphi[1] = 0x00; // set high temp alarm at 26C.
to 
temphi[1] = 0x1A;

temphi[0] = 0x00; // set high temp alarm at 26C.

better

uint8_t temphi[3]= {0};
temphi[0] = 0x03; // register
temphi[1] = 0x00; // HiByte
temphi[2] = 0x1A; // LowByte

ret = HAL_I2C_Master_Transmit(&hi2c2, TMP102_ADDR, temphi,3, 100);

Hint: An array is always passed as an address.

hth

padawan

[rasem]

Hi Padawan.

Great solution. It is working now after sending 3 bytes togther.

Thank you very much.

Rasem

[GOB]

Hi ,

Can some explain the below please ?

uint8_t temphi[3]= {0};
temphi[0] = 0x03; // register
temphi[1] = 0x00; // HiByte
temphi[2] = 0x1A; // LowByte

ret = HAL_I2C_Master_Transmit(&hi2c2, TMP102_ADDR, temphi,3, 100);

Not sure why these 3 registers are transmitted at the same time ? in my understanding should we just Transmit 0x03 and then use the _Receive function to read 2 registers. Do any one have sample code please ?

thanks

[padawan]

Hi GOB,

The code snipped shows how to write the registers.

The "ret" is the HAL Stat (HAL_OK)

if you want to read the Resiter you are right.

uint8_t temphi_reg[1]= {0};
uint8_t temphi[2]= {0};
uint16_t temphi_val = 0xFFFF; // If the I²c fails 

temphi_reg[0] = 0x03; // register

ret = HAL_I2C_Master_Transmit(&hi2c2, TMP102_ADDR, temphi_reg,1, 100);
if (ret== HAL_OK)
{
    ret= HAL_I2C_Master_Receive (&hi2c2, TMP102_ADDR,temphi,2 ,100);
}
// in temphi the val of the reg
if (ret== HAL_OK)
{
    temphi_val= (temphi[0]<<8)+ temphi[1];
}

 padawan

[GOB]

Thankyou Padawan,

ref datasheet "The temperature limits are stored in the T(LOW) and T(HIGH) registers in the same format as the temperature result, and the values are compared to the temperature result on every conversion." 

Does this mean only 12 bits carry useful data ?

in this case should we use the below:

// Combine the bytes

value = ((int16_t)temphi[0] << 4) | (temphi[1] >> 4);

// Convert the float value temperature value to Celcious, then to decimal format

value_THigh_C = value * 0.0625 * 100;

sprintf((char*)buf, "%u.%02u C\r\n", ((unsigned int)value_THigh_C), ((unsigned int)value_THigh_C % 100));

but i am getting 8000.00 C instead of 80.00C

Then i tried 

temphi_val= (temphi[0]<<8)+ temphi[1];

its giving me 80.80 C

any help is much appreciated please ?

[padawan]

HI GOB,

your are right. 

I don't have access to the sensor, so my code is more theoretical.

After checking the data sheet again, it should work as described below. As I said, in theory.

int16_t temp_val= (((temphi[0])<<8)+ temphi[1]);
int16_t temp_val12 = temp_val / 16
float temp = (temp_val12 *0.0625);

We shift the Highbyte to the upper byte of the 16Bit val, Add the low byte and dived by 16 (12Bit).

so we are care about negativ values

 theoretical ;)

This shows the 12Bit conversion.  

hth

padawan