CYW43907, glitch on GPIO_12 at hibernate exit

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cedric_roomz
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Hi,

We made a custom board based on the CYW43907 dev kit design using 1GC modules. On one of our prototypes there is a ~80usec high glitch on GPIO_12 which happens right after Hib wake is toggled.

The glitch happens almost instantaneously after the hib_wake toggle, and a few hundreds of millisecond before the firmware is actually running. 

cedric_roomz_1-1658920735708.png

 

I am not able to reproduce this on other boards, though they have the same firmware and same hardware.

 

The pin is clearly driven high during those ~80usec, and then high impedance  (we have a 100K pull down on the line)

 

cedric_roomz_0-1658920264063.png

 

I am not able to reproduce this on other boards, though they have the same firmware and same hardware.

When the device powers up without HIB_WAKE, I don't see the glitch.

 

What could cause such a glitch?

 

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Murali_R
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I am not able to reproduce this on other boards, though they have the same firmware and same hardware.

--> Are these your custom boards or the standard eval boards?

Is it possible to share the schematic of your custom board here?

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cedric_roomz
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It's a custom board, but strongly based on the eval board.

I won't be able to share the whole board here. But I can share some specific parts. Tell me what is needed for such an issue.

 

GPIO 12 is connected to the gate of a transistor with a pull down.

cedric_roomz_0-1658930012303.png

 

 

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cedric_roomz
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Hi,

Any update? We are starting a small production batch, and are seeing this issue on 10-20% of devices. I'll dig more in the coming days but I would appreciate some help in understanding possible causes. 

What we know so far:

- It affects only  ~10% of boards, we have not seen an OK board showing the issue later

- It happens very fast after the hib wake signal, is it in the bootloader?

- We have not found any short circuits. The likeliest pins for short circuits do not show the glitch

 

Thanks,

Cédric

 

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Hello Cédric

Apologies for the delay. I am checking with the hardware design team on this and will update soon.

Thanks

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cedric_roomz
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Thanks, do not hesitate to contact me shall they need more info.

I have controlled other GPIOs (0, 14, 15, 16) , they do not show the issue.

Could it be some multiplexing issue with a peripheral?

cedric_roomz_0-1662560629277.png

 

Cédric

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Do you see this issue when the uC_reset is isolated from the GPIO_12?

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cedric_roomz
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I'll try on Monday with Q4 and R42 removed (see schematic above). Do you expect another behavior without those?

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cedric_roomz
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With nothing connected to GPIO12, we still see the issue, a 80usec ON pulse when exiting hibernate, but now it is followed by ~900ms at ~2V, until the firmware initialize the GPIO as an output. 

Which makes sense since there is no pull down anymore.

 

cedric_roomz_1-1662970529928.png

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Have you checked with Murata? Since their module is being used here, haven't they been able to provide any insight?

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cedric_roomz
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Just raised the issue at Murata. 

Does this mean you have not found any possible leads in your end? Could there be something in the default bootloader which generates this glitch?

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Nothing at the moment. We'll keep looking at this to see if we can find anything.

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