TMP 117 read incorrect data occasionally.

Hi mingzhao ma,

Could you please show us the I2C transactions on oscilloscope?

thanks,

ren

I could not provide the capture on oscilloscope for the time being. I'll upload it when it is ready.

but our hardware engineer have had a test on Electrical characteristics and they are inline with datasheet.

I will attach the test data.

On software side, we use One-shot mode, and wait for 18ms for reading data after send a read request.

Best

Hi mingzhao ma,

Are you using AVG=00? By default, AVG=01 which corresponds to 125ms conversion time.

I look forward to seeing the oscilloscope pictures.

thanks,

ren

let's check software firstly.

At the beginning of communication, MCU send 0x0C04 to 0x01(Configuration Register)

and then wait for 18ms to read TMP 117 data.

so I think

MOD is one-shot mode, 11

AVG is No averaging 00. 

CONV is 000.

and the conversion time is 15.5ms according to "Table7.ConversionCycleTimein CCMode".

any other points I should pay attention to?

Hi mingzhao ma,

Yes, I agree that 0x0C04 configuration corresponds to One-Shot conversion with 15.5ms conversion time. You should be able to fetch the temperature result after your 18ms wait.

thanks,

ren

Hi, Schackmann

we thought of another probable reason of this issue. that is TMP 117 is accessed while a previous temperature reading function is executing.

what do you think of it?

best

mingzhao

Hi，

I think application layer should use mutex to prevent  this issue.

as our log shows, the error occur when 2 or more procedure is call at the same time.

OK case, read one by one:

=====address read before 541190088  541190089     
====buffer address  541190088
====buffer value  12
====buffer address  541190089
====buffer value  175
=====address read after 541190088  541190089  
=====gs_uc_temp_data_rx 12  175
=====read_temp 3247
=====ret 0
25.367188
=====address read before 541190088  541190089   
====buffer address  541190088
====buffer value  12
====buffer address  541190089
====buffer value  175
=====address read after 541190088  541190089
=====gs_uc_temp_data_rx 12  175
=====read_temp 3247
=====ret 0
25.367188


Failed Case, read at the same time:


=====address read before 541190088  541190089     -》 first read start
=====address read before 541190088  541190089     -》 second read start
====buffer address  541190088
====buffer value  12
====buffer address  541190089
====buffer value  175
=====address read after 541190088  541190089      -》 first read done
=====gs_uc_temp_data_rx 12  175
=====read_temp 3247
=====ret 0
25.367188
=====address read before 541190088  541190089     -》 third read start
====buffer address  541190088
====buffer value  12
====buffer address  541190089
====buffer value  175
=====address read after 541190088  541190089      -》 second read done
=====gs_uc_temp_data_rx 12  175
=====read_temp 3247
=====ret 0
====buffer address  541190088
====buffer value  255
====buffer address  541190089
====buffer value  12
=====address read after 541190088  541190089      -》 third read done error
=====gs_uc_temp_data_rx 255  12
=====read_temp -244
=====ret 0
-1.906250

OK, thanks for your support, and I will close this case.