Mon, Sep 13, 2021 at 08:51:05PM +0200, Martin Wache wrote:
So, back to the plan with the Raspberry Pi 2B. One problem that I wanted to solve is the power consumption of the DVB-T dongle when it is not in use. I found https://github.com/mvp/uhubctl which can switch off power on individual USB ports. I wrote a VDR shutdown script that does the following:
sudo service lircd stop uhubctl -p ... -a off sudo service vdr stop
I did not refine the uhubctl invocation yet. The physical port could vary.
An easy way to start up VDR could be a udev rule that would start up the lircd and vdr services when the USB DVB stick is plugged in. Obviously, if we power off the port during VDR shutdown, the adapter would have to be plugged into a different port.
A simpler option for the occasional use of VDR might be to simply write udev rules that will start up lircd and vdr when the DVB adapter is plugged in, and shut down the services when the adapter is removed. That would be too risky if recording timers are being used.
I am not yet sure whether powering off the USB port makes any difference, because the plastic case of the DVB stick feels slightly warm to the touch even when the port is supposedly powered off. It might be that some internal heat produced by the Rasberry is being dissipated via the USB port. The metal frame of the USB jacks feels a bit warm too.
I think that I must measure the input power of the Raspberry Pi as well as the voltage on the USB port when it is supposedly powered off.
Marko
Powersaving for DVB receivers - try the attached patch from glenvt18 glenvt18@gmail.com
This has worked for me for a few years without noticeable problems on both USB and PCI cards. I'm still on V2.20 by the way. There's a little bit of log chatter as it powers up/down receivers when VDR scans the EPG etc, but you can filter that I reckoned it saved around 3W at the mains for a 2-receiver server setup when I tested it back in 2016 - which adds up over time.
usbhubctl is a bit of a sledgehammer !
HTH
Richard