jainprince
Posts: 4
Joined: Thu Nov 14, 2019 10:20 am

Compute Module RUN pin

Thu Jan 16, 2020 12:07 pm

Hi Everyone,

I am using RPi compute module 3. There is a situation, where I want to disconnect the power of RPi. Is it acceptable, if I keep the LOW signal for long time(~ 30 min) on RUN pin(pin #177) to disconnect the power?

Thanks,
Prince

trejan
Posts: 1112
Joined: Tue Jul 02, 2019 2:28 pm

Re: Compute Module RUN pin

Thu Jan 16, 2020 12:14 pm

Pulling the RUN pin low will hold the SoC in reset. It doesn't disconnect power.

I don't think there would be anything bad about doing this but you'll have to wait for a Raspberry Pi engineer to confirm.

aBUGSworstnightmare
Posts: 1610
Joined: Tue Jun 30, 2015 1:35 pm

Re: Compute Module RUN pin

Fri Jan 17, 2020 5:43 am

I have no idea on your design, but if there would be the need for me to 'disconnect power' I would do this on the PMIC by using it's enable signal.
This will then really switch of power

Anyhow, holding the device in reset for a longer periid shouldn't be a problem.

jainprince
Posts: 4
Joined: Thu Nov 14, 2019 10:20 am

Re: Compute Module RUN pin

Fri Jan 17, 2020 6:57 am

trejan wrote:
Thu Jan 16, 2020 12:14 pm
Pulling the RUN pin low will hold the SoC in reset. It doesn't disconnect power.

I don't think there would be anything bad about doing this but you'll have to wait for a Raspberry Pi engineer to confirm.
Hi, thanks for your response.
I am new to this forum, how can I get in touch with Raspberry Pi engineer?

jainprince
Posts: 4
Joined: Thu Nov 14, 2019 10:20 am

Re: Compute Module RUN pin

Fri Jan 17, 2020 7:09 am

aBUGSworstnightmare wrote:
Fri Jan 17, 2020 5:43 am
I have no idea on your design, but if there would be the need for me to 'disconnect power' I would do this on the PMIC by using it's enable signal.
This will then really switch of power

Anyhow, holding the device in reset for a longer periid shouldn't be a problem.
Hi I designed in a way that, when the main power supply disconnects, RPi compute module running on battery power supply and also manages the power of other peripherals connected to compute module. And there might be a situation, when battery power is enough to boot the standalone RPi Compute Module, but when other peripherals connected to the module, starts draining the battery power, Compute Module power cycles as the power isn't enough now. And I have tested this, and it stuck in the power cycle loop. To avoid this situation, I have MSP430, this guy know when the power is not enough for Compute Module to power the other peripherals. In this case, MSP430 sends a low power signal to the RPI and RPi goes in shutdown state, and aftter 15-20(enough time for shutdown) seconds sending the low power signal to RPi, MSP430 keeps the RUN pin LOW to avoid the RPI to reboot again and again.

Please suggest, if you think, there could be a better design.

Thanks,
Prince

gsh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 1464
Joined: Sat Sep 10, 2011 11:43 am

Re: Compute Module RUN pin

Fri Jan 17, 2020 2:59 pm

Driving the RUN pin low for any length of time is fine, it will as previously said just hold the device in the reset state.
--
Gordon Hollingworth PhD
Raspberry Pi - Director of Software Engineering

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