FS85 Dev Board normal mode periodically turning on and off

[noobsplzwin]

Hello NXP team,

Hope all is well. I am using an FS85 dev board KITFS85FRDMEVM. I have successfully figured out our desired configuration in TestMode with Mirror registers and loaded the OTP to the board.

Now Im trying to use the board in normal mode to power up our ECU after ignition on. I pulled the DBG pin to the ground. Then turn on the SW2 ignition (Connect Wake1 to Vsup). The board starts periodically resetting itself with around 4-5 secs of power on and then off for 1-2 secs. At this time, all Vouts seem to be off other than Vboost.

But as soon as I follow the startup sequence to enter debug mode, connect DBG to Vusb, turn on the SW2, then remove the DBG shunt. Everything works perfectly.

Does anyone have experience with this or have an idea of why the SBC would enter such a state? 

Thanks in advance for any help

[diazmarin09]

Hello Leo,

I hope all is great with you. Thank you for using the NXP communities.

My apologies for the delayed response.

As we know, the Normal mode or Debug mode is defined at startup depending on the DBG pin level. Based on your description DBG is grounded, which is correct.

Could you please share a short video or images about the process that you are following to enter in normal mode?

Regards,

David

[noobsplzwin]

Hey Dav,

Thanks for ur response. Appreciate it. 
As u can see in the video. Before I turn on the(Sw1 to Vbat, Wake1 to On) dev board. I have connected the DBG pin to GND(J15-16). But all the bucks are turning off repeatedly.  

https://1drv.ms/v/s!AroaUORzQN0LkPNBXaSHTzpqX8Pnjg?e=4xDRgf
I'm not able to directly attach a video here. So here is the one-drive link to the video.

Please let me know if you need anything else.

Regards,
Leo

[diazmarin09 · Accepted solution]

Hello Leo, 

Thank you for your contribution. 

Could you please review the post below in case it is useful for you?

https://community.nxp.com/t5/Power-Management/KITFS85FRDMEVM-FS8530-Turns-Itself-Off-After-5-Seconds...

I hope this information helps. 

Regards,

David 

[noobsplzwin]

Hey David,

Again, thanks for the quick response. This looks like exactly my problem. Except our application needs to meet Asil D, so we'd need to use it in the normal mode and send the WD refresher. 

Right now I am trying to do this using the S32k3 dev board I have along with the SBC dev board. I noticed that in order to connect the SPI to another MCU. I will need to remove R13, R41, R42, and R43 to disconnect the KL25Z. Is there any way we can directly use KL25Z or GUI to close the Init phase (once RESETB is released high) within the 256ms window, and then refresh the watchdog?

Another question is, in order to close the init fs within the 256ms time frame, we'd need to monitor the state of RSTB(maybe interrupt or something) and Write the desired data in the FS_I_Register_A. But from my understanding, the main function of RSTB is to reset the MCU, which should be connected to the MCU reset pin. 

So what should be our schematic design here? Connect RSTB to both MCU reset and a digital interrupt IO?

Regards,

Leo

[diazmarin09]

Hello noobsplzwin,

My apologies for the delayed response.

1. You are correct, this kit uses a KL25Z MCU to communicate with FlexGUI. It is also possible to connect the SPI to another MCU. In this case, remove R13, R41, R42, and R43 to disconnect the KL25Z MCU and connect the external MCU.

The INIT_FS can be entered using the GOTO_INITFS bit in the FS_SAFE_IOs register.

2. You may use the KITFS85AEEVM Schematics as a reference for your design, I mean, the RSTB pin. It is connected as an input pin to the MCU (using a pull up resistor).

I hope this information helps.

Regards,

David