Strange timing when reading from the serial port

[Chris Stankevitz]

Chris Stankevitz wrote:
> Q: What is the source of the alternating +/- 5ms bias that comes and 
> goes every few seconds?

This helps: add these lines to /boot/device.hints and reboot

hint.sio.0.flags="0x20"
hint.sio.1.flags="0x20"

Chris