MSP432P401R: MSP432P401R Launchpad and TMP100 temperature sensor issue

David,

  My suggestion below for using a known-working program to read I2C assumes that you are working from a LaunchPad. If this is not correctly, the below may not work for you. If that's the case let me know and we can try something else.

 First I might try running one of the TI Driver (uses a TI-RTOS) example that's known to exercise the I2C to read a temperature. The "i2ctmp007" example under TI Resource Explorer / Software / SimpleLink  reads an I2C temperature sensor (TMP007) from the TI Sensor Hub boosterpack. It uses a different EUSCI instance and I2C address (the latter you can change by editing the variable  TMP007_OBJ_TEMP in the i2ctmp007.c source file).

This program simply reads the temperature and outputs the values to the backchannel UART.

This should at least allow you to see if the hardware or software is at fault. (Though it's suspicious that you are not getting an ACK, which suggests a connection problem or perhaps addressing issues.)  Running the above program at least gives you a known-working starting point. 

FOR MORE INFORMATION, see the SimpleLink Academy  "Multi-threaded RTOS Thermostat" module to learn how to use the Sensor Hub boosterpack and read temperatures via I2C. 

Regards,

  Bob

Hi Bob,

I changed my SCL and SDA pullup resistors and the TMP100 initialization works.

My next problem is reading the temperature data using driverlib APIs.

I had a look at non-rtos examples  (tmp006 code for the educational booster mkii, and  the simplelink drivelib example 'i2c_master_rw_repeated_start-master_code.c')

I tried 2 code implementations: (Added lines numbers for clarity)

Code 1 is  lines 1-12 and does not work.

This hungs up  the 2nd time i execute on line 3. I have noticed that

SDA is low on the 2nd run. The only way i can get around this is to power cycle the TMP100 IC.

Code 2  is just lines 1, 4-12. (i.e lines 2 and 3 are not included).

This sort off works  however when i use 2 TMP100 devices with different addresses,

when the code is run targeting one TMP100 , it reports the temperature of the other device. It seems the

values in lines 5 and 7 are from the previously read TMP100.

Note: I perform the following:

Read_Sensor1->Read_Sensor2->Read_Sensor1.....etc

Where Read_SensorX runs the code  for the specified TMP100.

The lines 6 and 7 are in that order due to a comment in the 'i2c_master_rw_repeated_start-master_code.c' code which uses that order.

This is the comment:

           /*

            * Switch order so that stop is being set during reception of last

            * byte read byte so that next byte can be read.

            */

Actually when i switch lines 6 and 7, the temperature reading does not change even when i heat or cool the TMP100

Code :

float TMP100ReadTemperature( uint_fast16_t  SlaveAddress)

{

   volatile uint16_t temp = 0;

   volatile uint16_t val = 0;

   volatile uint16_t valscratch = 0;

   float tempval;

1.     MAP_I2C_setSlaveAddress(EUSCI_B2_BASE, SlaveAddress);

2.   MAP_I2C_setMode(EUSCI_B2_BASE,EUSCI_B_I2C_TRANSMIT_MODE);

       /* Send start and the first byte of the transmit buffer. */

3.       MAP_I2C_masterSendMultiByteStart(EUSCI_B0_BASE,  0x00]); // Point  to Temperature register

4.    MAP_I2C_masterReceiveStart(EUSCI_B2_BASE);

5.    val = MAP_I2C_masterReceiveMultiByteNext(EUSCI_B2_BASE);// Get MSByte

6.    MAP_I2C_masterReceiveMultiByteStop(EUSCI_B2_BASE);// Send STOP

7.    valscratch = MAP_I2C_masterReceiveMultiByteNext(EUSCI_B2_BASE);// Get LSByte

8.    val = (val << 8) & 0xFF00;  // Shift to top MSB

9.   valscratch = valscratch & (0x00FF);

10.  temp = val | valscratch;

11.   temp = temp >> 4;

 12.    tempval = (float)temp* 0.0625;

}

Hi David,

Looks like you replied when i was posting my problem with reading temperatures. I will look at the tmp007 driverlib example. Thanks

David

I have tried to use some of the concepts employed in his post link  (tmp007 with interrupt mode) with my tmp100 (non- interrupt mode) and run into problems indicated in my September 14, 2017 post.  The 'i2c_driver.c' code performs  some of the i2C status checks (e.g NAK, START, STOP) and i would like to know how i can implement similar checks in my non-interrupt mode of operation.