RK3066 Measy U2C stick power consumption

Today I've done an experiment I was curious about: measuring my Measy U2C's (RK3066 CPU) real power consumption.

Setup

      My current setup is the above Measy U2C powered (to the DC-5V Micro USB) by an HTC phone's USB power adapter (rated 5V 1A) connected to the DC-5V Micro USB port, through a breakout USB cable that allows me to place a multimeter in series (for current measurement) or in parallel (voltage).


The power consumers:

- The Measy U2C RK3066 stick running Picuntu Linux 0.9 RC3 (Xubuntu 12.10 Quantal Quetzal)
- A Logitech K400 wireless keyboard+mouse with its USB dongle in the USB 2.0 port
- A TP-Link TL-WN422G 802.11g WiFi stick in the side Micro USB
- An Acer X233H FullHD monitor to the HDMI connector



The variables:

- The stick is running Linux from a Samsung 32 GB Class 10 MicroSD
- RK3066 idle means just logged in XFCE with only conky running
- At idle the CPUs run at 252 MHz all the time ("ondemand" governor)
- RK3066 load means two threads at 100% CPU usage [1]
- For some reason my stick's CPUs won't go beyond 1.2 GHz at full load
- Picuntu kernel's DDR memory frequency is set at 300 MHz (below my stick's DDR3 chips' specs)
- Internal WiFi+BT, webcam, micro, and AV Out are not working from Linux (YET!)

Raw Measurements

- Current (in Amperes):

RK3066 idle = 0.24 A
RK3066 load = 0.5 A
RK3066 idle + HDMI connected (720p) = 0.29 A
RK3066 idle + TP-Link WiFi = 0.41 A
RK3066 idle + Logitech K400 = 0.28 A
RK3066 idle + TP-Link WiFi + Logitech K400 = 0.45 A
RK3066 idle + TP-Link WiFi + HDMI connected (720p) = 0.47 A
RK3066 idle + TP-Link WiFi + Logitech K400 + HDMI connected (720p) = 0.5 A
RK3066 load + TP-Link WiFi + Logitech K400 + HDMI connected (720p) = 0.75 A
RK3066 suspend = 0.13 A

- Voltage (in Volts):

In open circuit configuration (unconnected) = 4.77V
With RK3066 idle + WiFi + K400 + HDMI = 4.58 V
With RK3066 load + WiFi + K400 + HDMI = 4.52 V