s9keaz128a MLH reset pin problem,MCU can not boot properly

[lynger]

Hi all,

I'm using s9keaz128a MLH 2N45K CTHE 1811G for a automotive project as a motor controller. However the board doesnot running properly as expected. It could not boot. The 5V VCC is OK with no noise, But the #s9keaz128a Reset pin (without capacitor) is poor like this:

and with capacitor ( 2.3V plus Sawtooth Wave noise):

the reset pin(pa5/reset_b 63 pin) circuit:

the reset should be 5V. 

[lynger]

Problem solved.

It's caused by the NMI_b.The board's NMI_b pin was used as a gpio and connect to a BJT with a pulldown resistor.So the fresh new MCU was interrupted again and again. The MCU never boot properly not to mention flash firmware.

We will change the board gpio next time.

[Robin_Shen · Accepted solution]

Hi Lynger Zhu,

Please refer: How To Sucessfully Program a Custom made Kinetis Microcontroller Board.
Notice the circuit of these pins:

NMI_b          external pullup resistor

SWD_CLK   external pulldown resistor

SWD_DIO   external pullup resistor

You can attach your circuit here, so that we can check it.

If still not work, please try to use 3.7uF Vdd bypass capacitor.

Best Regards,

Robin

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