Raspberry Pi 3 – NTP problem solved – some power issues

I got a Raspberry Pi 3 recently and installed the official Raspbian image from raspberrypi.org.

I came across a couple of issues:

  1. NTP would not sync.

ntpq -p would show that all the servers were in a state of .INIT.

ntpdate would work but ntpd would not.

It turns out that the kernel driver for the built-in WiFi chipset can’t handle the NTP packets over UDP. The solution is to add the following to /etc/rc.local:

/sbin/iptables -t mangle -I POSTROUTING 1 -o wlan0 -p udp --dport 123 -j TOS --set-tos 0x00

and reboot.

This is discussed on the raspberrypi.org forums at https://www.raspberrypi.org/forums/viewtopic.php?f=28&t=141454

  1. Power management is a problem running it off an Anker 10-Port charger (http://www.amazon.com/Anker-10-Port-Charger-Multi-Port-PowerPort/dp/B00YRYS4T4)

I knew that the Raspberry Pi 3 drew more power but it seems to be unstable with this particular charger. That’s not to say the charger is at fault, it’s running 6 other Raspberry Pis quite happily but they are older models and I don’t think the ports supply the required current. I’m ordering a 5v 2.5A power supply to see if that resolves the issue.

The WiFi chip needs to have power management disabled to get it to be responsive.  To do that, you can create a file /etc/modprobe.d/8192cu.conf and add the following:

options 8192cu rtw_power_mgnt=0 rtw_enusbss=0

I’m not certain this is addressing my immediate problem but once I get a more powerful power supply, I’ll be able to check.