MPC5744 & MC33907 Wakeup by CAN

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MPC5744 & MC33907 Wakeup by CAN

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ahmedsoubky
Contributor II

Hello Everybody, 

 

We have a question to you regarding the CAN wakeup by the MC33907 system basis chip. 

 

The configuration we have is the SBC provides the power to MPC5744 microcontroller and due to CAN activity the SBC wakes up and powers up the microcontroller and starts up the system accordingly. 

 

During the shutdown sequence, which can take up to 2 seconds, the CAN controller is stopped and we can't receive CAN frames in the microcontroller any more. And in case CAN wakeup event is detected by SBC, we need a notification from the SBC to the microcontroller that CAN frames are were received in order to cancel the shutdown sequence and startup the system again. 

Can you please help us regarding this issue ? 

 

Thanks in advance, 

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reyes
NXP TechSupport
NXP TechSupport

Hello,

When you say CAN controller, is it MC33907 CAN phy configured with CAN_MODE in sleep mode [x0]?

 CAN_mode.png

 

If yes, why do you stop the CAN during shutdown process?

If you set it in LISTEN only mode, you could listen the CAN traffic at MCU level and take decision to go to LPOFF or not just before sending the SPI command Go_To_LPOFF to the MC33907.

 

To go to LPOFF the SBC wait for a SPI command from the MUC. So it’s MCU decision to put the SBC in LPOFF mode and when this command is received, nothing can stop the process. However, if the SBC goes in LPOFF mode and CAN traffic is still there, than it will wake up immediately.


Have a great day,
Jose

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ahmedsoubky
Contributor II

Hello,

No, we don't set MC33907 CAN_MODE into sleep mode in the shutdown. It is simply we put the MC33907 in LPOFF.

We decided to set MC33907 CAN_MODE in LISTEN ONLY mode during the shutdown. However, the problem is the CAN controller from the microcontroller side will be in SLEEP mode. So can't receive CAN frames in the microcontroller. 

So, I was asking if there is any way to detect CAN activity on the SBC other than CAN frames that are sent to the microcontroller. 


Thank you very much, 

Ahmed

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reyes
NXP TechSupport
NXP TechSupport

Hi Ahmed,

No, the SBC is not giving indication about CAN traffic thru SPI for example.

You should not stop the CAN controller in the MCU until you send the GoTo LPOFF command to the SBC in order to listen the network till the last moment before SBC goes to LPOFF.


Have a great day,
Jose

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ahmedsoubky
Contributor II

Hi Jose, 

There is a limitation that we can't stop the CAN controller during shutdown process. 

#1 Is there any possibility that the SBC gives an indication of CAN frames received to the MCU ? 

In the SBC reference manual:

pastedImage_2.png
Which hypothetically means a CAN wake-up event can be configured to generate a low pulse on the INTB pin which is connected to the microcontroller. 

However, no more information was found how to configure the INTB to react to CAN wake-up event.

#2 Was this assumption correct or not ?

 
Appreciate your support, 

Ahmed

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reyes
NXP TechSupport
NXP TechSupport

Hi Ahmed,

 

Even if the shutdown process was started and the SBC goes to LPOFF mode while CAN traffic are still there then the SBC will wakes up immediately by CAN but we can’t avoid the got to LPOFF process as soon as the SPI command is sent to the SBC and unfortunately, the SBC does not have the capability to report CAN traffic to the MCU unless thru TXD/RXD activity to the MCU.

 

Have a great day,
Jose

 

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