GPIO voltage Level for wake-up interrupt

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WonjinHan
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Dears.

Now I tried to configure gpio port 6_1 as input, HighZ, CMOS for wake-up interrupt of DeepSleep in CYT2B95CAS. After MCU goes Deepsleep, when I put the signal which has the voltage level of 3V divided by resister divider(Higiside:4K, Lowside:3.3K) from ignition S/W(12V) to this port, MCU got waken up from Deepsleep.

I understood as the following for CMOS drive mode

1. VDDD : 5V

2. Input Voltage High Threshold in CMOS : 0.7 × (VDDD or VDDIO_1 or VDDIO_2) : 3.5V

3. Hysteresis Area : From 1.5V to 3.5V

4. Input Voltage Low Threshold in CMOS : 0.3 × (VDDD or VDDIO_1 or VDDIO_2) : 1.5V

 

The voltage level of 3V puts to port6_1 is in Hysteresis Area so I believe that is correct MCU should not be waken up by 3V. That means that in the case of voltage leve to port6_1 is more than 3.5V, it's common that MCU should be waken up. Could you review my understanding that is Right or Wrong?

 

Best regards,

Kevin Han.

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yanf
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Hi Kevin,

Can you further explain how you get the 3V voltage from 12V power supply?

3.3K and 4K resistor dividers seems to give a  5.4V output if put straightforwardly in series connection.

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And YES to your next question. Only if input voltage is higher than 3.5V on GPIO pin will a wakeup signal be issued.

 

Best Regards,

Finn

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yanf
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50 replies posted 50 sign-ins 25 solutions authored

Hi Kevin,

Can you further explain how you get the 3V voltage from 12V power supply?

3.3K and 4K resistor dividers seems to give a  5.4V output if put straightforwardly in series connection.

无标题.png

And YES to your next question. Only if input voltage is higher than 3.5V on GPIO pin will a wakeup signal be issued.

 

Best Regards,

Finn

WonjinHan
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Hello Finn.

I really appreciate your reply.

 

That’s my mistake to describe it.

Normally the voltage level of Ignition Battery is 12V as I  told. 

In this case of my measurement, Ignition Battery goes down to 7V so GPIO gets almost 3V.

 

And YES to your next question. Only if input voltage is higher than 3.5V on GPIO pin will a wakeup signal be issued.

=> I got your point and need to measure there was transient voltage over 3.5V  that comes GPIO Schmitt trigger out when ignition S/W is on.

 

Thanks and best regards,

Kevin.

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yanf
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You are very welcome, Kevin 🙂 

Best Regards,

Finn

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