TJA1043 not going to sleep

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TJA1043 not going to sleep

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Amine
Contributor I

Hello NXP Support,

I am trying to switch to sleep mode following all the recommendations in the NXP official documents. However, the only issue that happens is that the STB_N signal is going back to HIGH just after the ROT went LOW. This triggers back a local wakeup and the Hardware is back to Normal mode.

 

Is there any known reason for the STB_N signal to switch to HIGH during transition to sleep mode ?

 

FYI: In my software, there is nothing software related that could trigger the STB_N to be back to HIGH during the transition to sleep mode. Also, the CANoe software is not even used to avoid bus wakeup. 

 

Thank you in advance.

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4 Replies

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Amine
Contributor I

According to the following screenshot, the STB_N is set HIGH at the same time the microcontroller is going to sleep (ROT set to LOW). At that exact time, the debugger is suspended and the software is not influencing the STB pin. In order to confirm it, I even changes the STB pin direction to input before sending the SBC to sleep mode to ensure that the software is not the source cause. 

Do you think of any reasons for this behavior ?

Amine_0-1692275320881.png

 

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diazmarin09
NXP TechSupport
NXP TechSupport

Hello Amine,

I hope all is great with you. 

In this case, I would like to recommend the post below. Is your program within the recommended procedure? 

https://community.nxp.com/t5/i-MX-Processors/Putting-TJA1043-to-sleep-after-powerup/m-p/1021180

Regards,

David

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ramprakash07
Contributor III

Based on your description, it seems like you're following the correct steps to transition the TJA1043 to sleep mode. However, the STB_N signal going back to HIGH during the transition is indeed unusual.

One possible reason could be a hardware issue. The STB_N signal is typically controlled by a microcontroller, and it should remain LOW during the transition to sleep mode. If it's going back to HIGH, it could be due to a hardware glitch or a problem with the microcontroller. You might want to check the hardware connections and the microcontroller's operation.

Another possibility is that there's some kind of electrical noise or interference that's causing the STB_N signal to go HIGH. This could be due to a variety of factors, such as a noisy power supply, electromagnetic interference, or even a problem with the CAN bus itself. You might want to check the electrical environment and make sure there's no potential source of interference.

Finally, it's also possible that there's a problem with the TJA1043 itself. While this is less likely, it's still a possibility. You might want to try using a different TJA1043 to see if the problem persists.

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Amine
Contributor I

Hello ramprakash07,

Thank you for the hints. 

Indeed, this is what I had in mind as well (3 possibilities) but I do have another software which runs on the same hardware and I am able to perform a proper go to sleep. The issue is that the same steps are performed in my program which lead to a transition to sleep mode.

However, using my program, the STB_N pin is going HIGH once the Debugger shows "suspended". This means that the STB_N pin going HIGH is not caused by the software. Also, after removing the debugger, I see that the hardware is a reset loop: everytime it tries to go to sleep, the STB_N pin triggers a new wakeup, then it tries again to go back to sleep because there is no activity on the bus. This proves that it's not a hardware noise nor a glitch knowing that the behavior is systematic.

Best regards,

Amine

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