TMP117EVM: Writing data to the registers

Christopher Broderick

Part Number: TMP117EVM
Other Parts Discussed in Thread: CC3220SF, TMP117, TIDA-01624

Hello,

I have the TMP117EVM linked to my CC3320SF board to read ambient temperatures in a room. I cannot seem to find a way to write the to the registers on the TMP117EVM using the I2C drivers provided in the CC3220SF SDK. Can someone help?

I used this as a template to interface with the sensor:

http://dev.ti.com/tirex/#/?link=Software%2FSimpleLink%20CC32xx%20SDK%2FExamples%2FDevelopment%20Tools%2FCC3220SF-LAUNCHXL%2FTI%20Drivers%2Fi2ctmp006%2FTI-RTOS%2FCCS%20Compiler%2Fi2ctmp006

Snippet of my code:

/* setting the high limit temp */
HTWriteBuffer[0] = High_Lim_Reg;
HTWriteBuffer[1] = highliml;
HTWriteBuffer[2] = highlimh;
i2cTransaction2.slaveAddress = TMP117_address;
i2cTransaction2.writeBuf = HTWriteBuffer;
i2cTransaction2.writeCount = 2;
i2cTransaction2.readBuf = HTReadBuffer;
i2cTransaction2.readCount = 2;

^I am trying to write a 2 byte value to the High temp limit register and store the highest temp I want to see but when I read from the register to check if it was written correctly the value I sent is not returned and I get the default value of 8000h (0x8000).

over 5 years ago

0 Amit Ashara over 5 years ago

TI__Guru**** 244380 points

Hello Chris,

The correct method to write to the TMP117 using the SimpleLink MCU would be

HTWriteBuffer[0] = High_Lim_Reg;
HTWriteBuffer[1] = highliml;
HTWriteBuffer[2] = highlimh;
i2cTransaction2.slaveAddress = TMP117_address;
i2cTransaction2.writeBuf = HTWriteBuffer;
i2cTransaction2.writeCount = 3;
i2cTransaction2.readBuf = HTReadBuffer;
i2cTransaction2.readCount = 0;

We have the reference design TIDA-01624 which uses the BLE MCU to write to the TMP117 and you may use it as a reference code.

0 Christopher Broderick over 5 years ago in reply to Amit Ashara

Intellectual 910 points

Thank you for clarifying how to write the data now could you clarify how to read the data from this register. I though it would be similar to reading from the temperature register which was as follows:

txBuffer[0] = Temp_Reg;
i2cTransaction.slaveAddress = TMP117_address;
i2cTransaction.writeBuf = txBuffer;
i2cTransaction.writeCount = 1;
i2cTransaction.readBuf = rxBuffer;
i2cTransaction.readCount = 2;

if (I2C_transfer(i2c, &i2cTransaction)) {
temperature = (rxBuffer[0] << 8) | (rxBuffer[1]);
temp_p = temperature * 0.0078125; ;
Display_printf(display, 0, 0, "Temperature is: %0.1f [C]", temp_p);
}

what i wrote:

txBuffer[0] = High_Lim_Reg;
txBuffer[1] = highliml;
txBuffer[2] = highlimh;
i2cTransaction2.slaveAddress = TMP117_address;
i2cTransaction2.writeBuf = txBuffer;
i2cTransaction2.writeCount = 3;
i2cTransaction2.readBuf = rxBuffer;
i2cTransaction2.readCount = 2;

if (I2C_transfer(i2c, &i2cTransaction2)){
high_temp = (rxBuffer[0]) << 8 | (rxBuffer[1]);
Htemp_p = high_temp * 0.0078125;
Display_printf(display, 0, 0, "High is: %0.1f [C]", Htemp_p);
}

Unfortunatley I am not getting the value I am storing which would be 24 degrees C which in binary would be:
24 degrees C = 0000 1100 0000 0000
according to the data sheet. the number I am getting is 0.5 which is:
0000 0000 0100 0000

Calculation used to determine binary number based on TMP117 data sheet:
Temp desired / 0.0078125 = binary of that temperature

0 Amit Ashara over 5 years ago in reply to Christopher Broderick

TI__Guru**** 244380 points

Hello Christopher,

I don't have a setup to test it out, but it should look something like the following

txBuffer[0] = High_Lim_Reg;
txBuffer[1] = highliml;
txBuffer[2] = highlimh;
i2cTransaction2.slaveAddress = TMP117_address;
i2cTransaction2.writeBuf = txBuffer;
i2cTransaction2.writeCount = 3;
i2cTransaction2.readBuf = rxBuffer;
i2cTransaction2.readCount = 0;

I2C_transfer(i2c, &i2cTransaction2);

txBuffer[0] = High_Lim_Reg;
i2cTransaction2.slaveAddress = TMP117_address;
i2cTransaction2.writeBuf = txBuffer;
i2cTransaction2.writeCount = 1;
i2cTransaction2.readBuf = rxBuffer;
i2cTransaction2.readCount = 2;

if (I2C_transfer(i2c, &i2cTransaction2)) {
high_temp = (rxBuffer[0]) << 8 | (rxBuffer[1]);
Htemp_p = high_temp * 0.0078125;
Display_printf(display, 0, 0, "High is: %0.1f [C]", Htemp_p);
}

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TMP117EVM: Writing data to the registers