Sampling rate

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Sampling rate

Unread postby Memo » Tue Jul 03, 2018 2:14 am

Good day!

I am interested in acquiring a couple of SmartPower2 devices to use with my ODROID XU4 to obtain energy consumption of an execution that may take a few hundred milliseconds.

I heard the default sampling rate is 1 Hz, which is too coarse for what I need. I also heard you can increase it to up to 20 Hz, which is still far from perfect, but much more viable.

I would like to know 2 things:

1 - How much can I increase the sampling, and what accuracy will the energy value that is reported have?
2 - Can I obtain the output via UART (with a USB cable connected to a computer) in a way that the computer is not required to connect to a different network? I plan on hooking it up to a server, so I can run my benchmarks (remotely) in the datacenter the computer is in.

Thank you for your time to read and respond to my questions. I hope the SmartPower2 is the adequate solution for my problem.
Cheers!
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Re: Sampling rate

Unread postby odroid » Tue Jul 03, 2018 7:57 am

Try the latest firmware v1.4 for UART access.
viewtopic.php?f=86&t=30870#p224167
https://wiki.odroid.com/accessory/power_supply_battery/smartpower2#receving_power_data_via_microusb_cable

BTW, could you build the SmartPower2 firmware?
https://wiki.odroid.com/accessory/power_supply_battery/smartpower2#build_firmware
If yes, we will try to let you know which code should be changed to adjust the sample rate.
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Re: Sampling rate

Unread postby Memo » Tue Jul 03, 2018 12:34 pm

I believe so, given that I use Ubuntu 16 LTS.

But before I get to that, I need to consider my alternatives regarding sampling rate and achievable accuracy. Could you clarify how accurate the energy consumption metric is, and how high I can get the sampling rate without sacrificing accuracy?

Thank you.
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Re: Sampling rate

Unread postby odroid » Tue Jul 03, 2018 2:03 pm

Read the INA231 datasheet page 14 and let me know your estimated error rate in 20Hz(~4.7ms) sampling rate.
http://www.ti.com/lit/ds/symlink/ina231.pdf
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