I have been using the Intel Joule and was wondering if there was more information about lowering the power consumption under light loads and idle conditions. specifically, I was wondering if there was a reference that outlined things like lowering the CPU operating frequency and completely powering down integrated peripherals when they are not in use.
I will try to help you with this. Unfortunately there is no official documentation regarding how to lower the power consumption on Joule, nevertheless, as you mentioned, powering off some interfaces such as Bluetooth and Wi-Fi might have a positive effect on the power consumption.
If you'd like to power off Bluetooth, you can use the command rfkill block bluetooth. If you'd like to turn off the Wi-Fi interface you can use the command ifconfig wlp1s0 down.
Not using the graphical interface will also affect the power consumption, so if your priority is low power consumption I'd suggest you to keep startxfce4 off and kill it in case you have already started it.
I hope this information helps you.
Disabling the Wifi does seem to save a decent amount of power. Is there a command to turn of the entire GPU subsystem, rather than just not having xfce up? Is there one for running lower clock speeds? it looks like /proc/cpuinfo reports the cores at 800MHz when idle. Is it possible to operate slower?
Thank you for your help and support.
According to /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies it is not possible to change the CPU speed lower than 800MHz, nevertheless, it should be possible to change the CPU's max speed. However, this has not been officially tested or validated and it might not even work or damage your board. So, I do not encourage you to try it but if you'd like to test if this helps in your project, I suggest you to follow this guide: https://software.intel.com/sites/default/files/comment/1716807/how-to-change-frequency-on-linux-pub.....
I hope this helps you.
I had changed some of the default BIOS options, but at an idle command prompt the entire dev-kit was drawing 130 mA @ 12.0V with WiFi enabled. With WiFi disabled it lowered to 73mA @ 12.0V.
Thank you for the response, I appreciate it. Have you been running any processing intensive code on it yet? If yes, what kind of power draw are you seeing?
I was considering revisiting this, but was wondering if you could point me to documentation about the processor that included descriptions of its settings, capabilities, register mappings, or timing information for the processor itself as well as the integrated peripherals?
Thanks in advance,
Don't worry, if you have any updates please post them here.
Regarding the Joule's documentation, you can find all the available documentation in https://software.intel.com/en-us/iot/documentation?field_topic_tid=79497&value=83295. You might be interested in the Joule's datasheet ( https://software.intel.com/en-us/articles/intel-joule-module-datasheet), however, detailed information about the Joule's processor is not available.
Also, if you ever have any other doubts, please don't hesitate to come back to the community. We'll try to help you in any way we can.