Power consumption (AxelLite)

Info Box Applies to Axel Lite

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	THIS PAGE IS OBSOLETE, DON'T USE IT AS REFERENCE
The new documentation is available here: AXEL_Lite_SOM/AXEL_Lite_Hardware/Electrical_Thermal_and_Mechanical_Features/Operational_characteristics

Introduction

Providing theoretical maximum power consumption value would be useless for the majority of system designers building their application upon AXEL LITE module because, in most cases, this would lead to an oversized power supply unit.

Several configurations have been tested in order to provide figures that are measured on real-world use cases instead. Please note that AXEL LITE platform is flexible, so it is virtually impossible to test for all possible configurations and applications on the market. The use cases here presented should cover most of real-world scenarios. However actual customer application might require more power than values reported here. Generally speaking, application specific requirements have to be taken into consideration in order to size power supply unit and to implement thermal management properly.

Tests have benn performed using DXLH SOM (Quad core CPU) limited to 1 or 2 cores actives.

Set #1

The following paragraphs report the power consumption measurements for the following typical use cases, using different core #/clock speed configurations, detailed in the following sections:

• U-Boot prompt
• Linux prompt
• CpuBurn
• GPU test
• VPU test

Testbed

Measurements have been performed on the following platform:

• Carrier board: AxelEVB-Lite Adapter + AxelEVB-Lite + DACU
• System software: XELK 2.0.0
• Power monitor: a custom current/voltage/power probe has been connected to the power rail of the SOM (for more details please refer to the net 2V8-4V5_SOM of the AxelEVB schematics).

Use cases results

The following table shows the summary result of data reported by INA226 at different checkpoints.

Checkpoint	1 core (mW)	1 core (mW)	2 cores (mW)	2 cores (mW)
	800MHz	1GHz	800MHz	1GHz
U-Boot prompt	2100	2100	2100	2100
Linux prompt	2300	2300	2300	2400
Cpuburn	2750	3000	3250	3850
GPU	2850	3100	3375	3950
VPU	3500/3800	3800/4000	3900/4200	4700/5000

Additional notes and reference:

• U-Boot uses a single core @ 800MHz
• At Linux prompt, a fixed clock frequency has been set (userspace governor)
• The number of cpuburn instances is equals to the number of cores
• burnCortexA9
  • https://packages.debian.org/sid/cpuburn
  • https://github.com/ssvb/cpuburn-arm
• GPU test: /unit_tests/gpu.sh
  • it's a Freescale script for GPU testing (video in overlay)
• VPU test: gst-launch -vvv playbin2 uri=file:///home/root/big_buck_bunny_1080p_surround.avi
  • decoding of a H.264 1080p30 video

Standby

The following paragraphs report the power consumption measurements when the system is in standby state.

Testbed

Measurements have been performed on the following platform:

• Carrier board: AxelEVB-Lite Adapter + AxelEVB-Lite + DACU
• System software: XELK 2.0.0
• Power monitor: INA226

Use case results

Voltage	Average current (mA)	Power absorption (mW)
3.3V SOM	51,7	170,61

Additional notes and reference:

• The system enters standby after launching the following commands:

# set wakeup source
echo enabled > /sys/devices/soc0/soc.1/2000000.aips-bus/2000000.spba-bus/2020000.serial/tty/ttymxc0/power/wakeup
# enter standby
echo mem > /sys/power/state