TMP112: Temperature sensor stops responding after a while

Hi Vignesh,

Can you please send waveform of I2C NACK and your schematic?  Please double check power when you receive the NACK.   

Thanks,

David

Hi David,

Thanks for the quick response.

I have attached the schematic of micro-controller and TMP112 section. (Actually we have removed Accelerometer chip from)

Regarding Power when received the NACK, it was exactly 3.3 volt near TMP112 and SCL and SDA when we check from multimeter.

Regarding the waveform, due to corono virus, we are in lockdown condition, so we don't have access to CRO.

My doubt is supply on SCL and SDA will be always provided (MCU_VDD is always ON), and supply for TMP112 (VDD_EXT_PER) will we enabled

only when we need to communicate with the chip, once we read the temperature will remove the supply for TMP112, but supply for SCL and SDA remains always ON.

If we provide supply for SCL and SDA and remove the supply for TMP112 will it cause any issue?

Regards,

Vignesh

Vignesh,

There should be no issue having I2C supply on and TMP112 supply off.  It is hard to debug this issue without the waveform.  How did you determine that the device is NACKing? 

Thanks,

David

Hi Vignesh,

Can you elaborate on what you mean by " not receiving ACK"?  

When I refer to the TMP112 NACK'ing I am referring to the 9 clock cycle of an I2C transaction.  The 9th clock cycle should be low after writing the device address.  If the 9th clock cycle is HIGH, then this is considered a NACK and the transaction failed.  How did you determine that the 9th clock cycle is HIGH?  You would need an oscilloscope of logic analyzer for this.

How long do you wait after turning on the TMP112 supply to read the temperature? 

Thanks,

David

Hi David,

Yes even i'm referring 9th clock cycle as an ACK bit.

In our case we are using Polling method, where we toggle SDA and SCL as per the data.

once we transmit out 8th bit of data, we will make SDA pin as Input and will check the SDA logic.

As i mentioned previously, we are receiving the ACK bit perfectly for few hours like 12 to 24 hours (taking sample every 5 minute once).

But after few hours later, TMP112 stops sending the ACK bit. 

In such cases till we unplug the battery and plug it back, TMP112 wont send ACK bit.

After powering ON the supply for TMP112 we have waited almost 10 seconds, and also we have retrying for 3 times with 10 seconds delay between each retry.

Is it due to making I2C supply ON and TMP112 supply OFF, is the device entering shutdown mode and becoming not responding?

Because we have our previous version of the device, like more than 5K devices are in site, working fine, only difference in that version is providing same supply voltage for I2C and TMP112 (like both will be ON or OFF at a time)

Below i'm attaching our previous design

Thanks,

Vignesh 

Vignesh,

There should be no issue having I2C supply on and TMP112 supply off when you are not polling the device.

Have you confirmed on this design that keeping both supplies on always resolves the issue?  This could be a timing issue that shows up over time.  To debug further I will need waveforms of the I2C transactions to confirm the transaction meets all the I2C specifications.  

Thanks,

David

Hi David,

Thanks for that.

If it is an timing issue, when we perform the NVIC_SystemReset or restart the device the timing issue should get resolved right?

Our micro-controller supports BLE so through BLE we are performing the Reset and restart, also we have performed Firmware update through BLE 

But after doing all this things still TMP112 doesn't work. Unplugging and plugging the battery is the only solution for the TMP112 read error.

And as i said we can't help you with the waveform, since we are in lock down situation due to Corona virus, i have got only Basic Multi-meter with me. 

Thanks

Vignesh

Vignesh - 

I work with David - one friendly suggestion, if feasible, for you now in this situation and for future working from home or remotely with a customer/co-worker situations; is to get a portable logic analyzer - I personally ordered one from Saleae a couple weeks ago and got it quickly and it allowed me to continue analyzing something.

in the past, i have also used the Intronix LSA, and this is OK device too -  and neither one of these companies is directly connected to TI, but IMHO their devices will help you in a time like this, to save the time debugging firmware or hardware. 

Links below - hope this finds you well and helps if you pursue it. 

https://www.saleae.com/

https://www.pctestinstruments.com/