PSoC5LP : USBFS component suspend operation

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MiNe_85951
Level 7
Level 7
Distributor - TED (Japan)
50 likes received 500 replies posted 50 solutions authored

Hi,

We are considering USBFS component for PSoC5LP.

Coded according to "USBFS_suspend" in Code Example.

Sleeps PSoC 5LP when there is no signal from the host for 3ms.

Wake up at the fall of USBIF Dp.

It works as expected.

However,

When the PC host side stops power supply and opens the USB signal line,

The USBIF Dp line voltage becomes unstable and PSoC5LP repeatedly wakes up and sleeps.

Do you know how to avoid this sleep and wake up behavior?

Regards,

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1 Solution

Once you wake-up, revert back the configuration. You should only pull-up while sleeping.

View solution in original post

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6 Replies
RodolfoGL
Employee
Employee
250 solutions authored 250 sign-ins 5 comments on KBA

You can try to pull-up or pull-down the USB pin before putting the device to sleep.

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MiNe_85951
Level 7
Level 7
Distributor - TED (Japan)
50 likes received 500 replies posted 50 solutions authored

Thank you for your reply.

Does it mean that the P15[6] pin setting of the USB Dp terminal is changed to a resistive pull-up / pull-down by API?

Regards,

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Yes. Refer to the PSoC 5LP datasheet, Table 6-7. USBIO Drive Modes.

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MiNe_85951
Level 7
Level 7
Distributor - TED (Japan)
50 likes received 500 replies posted 50 solutions authored

Thank you for your advice.

I will try changing the drive mode of USB IO.

Regards,

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MiNe_85951
Level 7
Level 7
Distributor - TED (Japan)
50 likes received 500 replies posted 50 solutions authored

As you advised, I was able to avoid indeterminacy by making USB IO resistive pull-up before entering sleep mode.

However, the resistive pullup of PSoC5LP is about 10 kΩ.

The USB 2.0 specification states that a pull-up resistor of about 1.5kΩ is required.

I think that this measure will not comply with USB 2.0.

Do you know any other best solution?

Regards,

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Once you wake-up, revert back the configuration. You should only pull-up while sleeping.

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