mke04 Reset signal

[MaxWood]

Hello everyone,
I would like to start using a controller from the mke04 series in my projects but I encounter a problem when I turn it on:
the Reset pin keeps changing from 1 to 0 quickly (about every 120µS).
The Reset pin is simply connected to a 10k pullup resistor..
What am I doing wrong?

[MaxWood]

Hi Celeste_Liu,
I have lost all hope of using this micro.. I have checked everything but I can't find anything wrong (also because there are only two power pins and two ground pins).
At this point I hypothesize two possible reasons: either both components that I purchased from Mouser are part of a defective batch or the reset behavior is regular because waiting for a first connection with USBDM...

[MaxWood]

Hi Celeste Liu
the reset keeps changing state as soon as I power the mcu with a perfectly clean stable power... without connecting the SWD port of the USBDM.
Could it be that, since the mcu are new, this happens while waiting for a connection with the SWD port?

[Celeste_Liu]

We also have EMC Design Tips for Kinetis E Family  for your reference. 

[Celeste_Liu]

Hi MaxWood,

Could it be that, since the mcu are new, this happens while waiting for a connection with the SWD port?

-> I don't think this is the case. 

[MaxWood]

Hi Celeste_Liu,
first of all thank you for your availability..
The Reset pin is connected via the 10K resistor R2 to pin 1 which is connected to +5 and in fact pin 9 is connected to ground because it appears to me to be connected to ground on the USBDM circuit.
The problem is that the Reset continues to change level as soon as I power the micro, without any software loaded as I have used new devices and have never been able to program them. Unfortunately I really don't know what to do as I have tried two new printed circuit boards and two new mcu just purchased (2 from Digikey and 2 from Mouser).
The interesting thing is that, the reset pin changes state in a coherent cyclic manner (about every 220mS) as if there was something inside the micro that intervened cyclically. I had thought about the intervention of the LVD device but it doesn't make sense because the supply voltage on the relative pins is exactly 5.05 V...

[Celeste_Liu]

According to your description, I think it's a hardware problem. Considering reliability, I still recommend that the reset_b use a separate pull-up power, instead of sharing the pull-up power supply with the SWD_DIO. This may bring about some stability issues. When the SWD is communicating, it may cause power fluctuations. If the pull-up is shared, it might lead to an unexpected reset.

[MaxWood]

Thanks Celeste,
I discovered a broken reset capacitor and replaced it!
Now it works..
Thanks a lot

[Celeste_Liu]

Hello,

You are very welcome, glad to help! Any new issues, welcome to create the new post.

BRs,

Celeste

[Celeste_Liu]

Hello @MaxWood ,

Thanks for your post. The standard practice for the RESET Pin is to use a 0.1uF cap along with a 10K pull-up resistor. Just like the following picture.

Please try again to see if the problem will still occur after adding the cap.

BRs,

Celeste

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[MaxWood]

Good morning everyone,
here I am again with my usual problem: Reset signal of the MKE04Z128.
I thought I had solved it by replacing the capacitor but I was wrong...
My circuit does not want to work. The Reset pin continues to go from 5V to 0 remaining at an average value of 2.6V and therefore I cannot use the mcu.
I think I connected everything correctly, I also replaced the microcontroller with a new one and on another printed circuit board but the result does not change. I attach the diagram relating to my project so maybe you can understand better.
Can someone please help me?
Thanks in advance, greetings to everyone

[Celeste_Liu]

And please double check your schematic about SWD part. I have doubts about the two yellow marked parts below and think they need to be modified. First, the RESET_pin should not be connected to pin1 of the SWD. Second, pin9 of the SWD should not be grounded. 

You can refer to the schematic of our FRDM-KE04. The schematic will be attached.

Have a nice day.

[Celeste_Liu]

Hello @MaxWood ,

I'm sorry to hear that. You mean that abnormal resets occur without pressing the reset pin. Does this happen after power  on or during program execution? If it occurs during program execution, it might be a software issue. Please refer to section "6.2.2 System reset sources" in the RM, and check them one by one(from 6.2.2.1 External pin reset (RESET) to 6.2.2.8 MDM-AP system reset request).

Hope it can help you.

BRs,

Celeste