Should the Kerberos power the Pi4 ?

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zanco
Posts: 10
Joined: Fri Apr 26, 2019 5:31 pm

Should the Kerberos power the Pi4 ?

Post by zanco » Mon Nov 16, 2020 7:48 pm

Hi,
I have strange issues with the Kerberos attached to a Raspberry Pi 4.

The Kerberos has one dipswitch off, so I can use 3 out of 4 receivers, currently with rtl_tcp to switch 3 different frequency bands.

However, if I want to reboot my Pi 4 that does not work with the Kerberos attached. Even after unplugging the USB C power from the Pi4 the power led stays on, I have to unplug either USB to the Kerberos or unplug the power from the Kerberos too.

If I power the Pi4 with Kerberos attached it often won' t boot, I have to remove the kerberos USB cable. have the Pi4 boot and plug in the Kerberos after that.

Is there a circuit diagram available? Looks to me the Pi4 gets power from the Kerberos over the USB cable to the Pi.

Thanks,

Ben - PE2BZ

rtlsdrblog
Site Admin
Posts: 2816
Joined: Mon Nov 19, 2012 11:54 pm

Re: Should the Kerberos power the Pi4 ?

Post by rtlsdrblog » Sun Nov 22, 2020 3:33 am

Try removing jumper JP2 on the PCB (which is next to the USB data port). That prevents power sharing between the Pi and Kerberos.

awdmesh
Posts: 51
Joined: Tue Oct 22, 2019 4:23 pm

Re: Should the Kerberos power the Pi4 ?

Post by awdmesh » Thu Dec 10, 2020 5:04 pm

I’m looking at this closer and here’s what I find.

I have a Pi4 with a wall plug that says output 5.1v 3.5a. I also have a plug for additional power to the KerberosSDr 5v 2.1amp.

With the external power applied to the KerberosSDr and the KerberosSDr plugged into the Pi4 I can observe that the Pi4 will not boot until the moment I either remove external power or the USB port from the Pi4 to the KerberosSDr.

I basically have to adopt a process where I boot the Pi4 with no KerberosSDr external power applied and then quickly apply the external power for the KerberosSDr.

The jumper you mention, I think I might have to do this, but I’m trying to understand what’s happening. Is the Pi4 detecting to much power is somehow getting to it and if so is it damaging to continue to do what I’m doing?

rtlsdrblog
Site Admin
Posts: 2816
Joined: Mon Nov 19, 2012 11:54 pm

Re: Should the Kerberos power the Pi4 ?

Post by rtlsdrblog » Thu Dec 17, 2020 1:53 am

awdmesh wrote:
Thu Dec 10, 2020 5:04 pm
I’m looking at this closer and here’s what I find.

I have a Pi4 with a wall plug that says output 5.1v 3.5a. I also have a plug for additional power to the KerberosSDr 5v 2.1amp.

With the external power applied to the KerberosSDr and the KerberosSDr plugged into the Pi4 I can observe that the Pi4 will not boot until the moment I either remove external power or the USB port from the Pi4 to the KerberosSDr.

I basically have to adopt a process where I boot the Pi4 with no KerberosSDr external power applied and then quickly apply the external power for the KerberosSDr.

The jumper you mention, I think I might have to do this, but I’m trying to understand what’s happening. Is the Pi4 detecting to much power is somehow getting to it and if so is it damaging to continue to do what I’m doing?
I think the problem to do with the Pi 4 not booting is not related to the power actually. I have seen a few posts on the Pi forums where other Pi 4 users claim that their Pi 4 won't boot with other USB devices plugged in, like an external HDD. Apparently updating the firmware or OS fixed it for some, but not everyone... I haven't been able to solve it that way either.

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