MKV31F128VLL10 sawtooth on reset pin

[renatodutra]

Hi, this if my first project with Kinetis, and I'm seeing a saw tooth waveform on the reset pin after a power up. I can connect to the target board and run/debug the application, however when I disconnect the probe (Jink) I see an oscillation on the reset_b pin.

First, I thought that this problem could be related to the fact that I was trying to use the NMI_b pin as GPIO. I changed the configuration on the board, so now the NMI_b is no longer a GPIO, but the problem still persists.

Any ideas what could be causing the problem or suggestions to fix it?

Any help appreciated. Thanks in advance.

[jorge_a_vazquez]

Hi renatodutra

You were using NMI-b as GPIO, now that NMI-b is no longer GPIO I suggest you check that the NMI pin is high during reset. Also, the NMI_b pin, if enabled, must not have any capacitance connected to it and as its default function it has a weak internal pullup, but an external 4.7 kΩ to 10 kΩ pullup is recommended.

Also I recommend you to check: Reset signal of K64, This thread is something similar to your case, it can help.

Hope this information helps you.

Have a great day,
Jorge Alcala

-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------

[renatodutra]

Hi Jorge,

Thanks for the reply.

In the end, the problem was related to an erroneous configuration.