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  • Case ID: 288828
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get lowest battery voltage

user82185

I am trying to measure my battery level on my nRF51822 beacon board through the internal ADC.

The chip is just advertising itself every 5 seconds.

The measurement works, I do get voltage readings. 

My issue is that the measurement needs to be done during the most power-hungry phase, which is probably the RF phase when the advertisement packet is sent out,

since that's when the voltage seems to dip the most.

My challenge is:

how to get the lowest battery voltage over time?

Since I can probably not continuously measure the voltage, my question boils down to these points:

  1. What's the proper way of usefully measuring the battery level when just advertising?
  2. Is there any event fired or any way to hook and execute code while an advertisement packet is being sent, a.k.a when the chip consumes the most power?
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    Hello,

    I think the key is to have consistent readings, and to get that you have to make sure the battery has roughly the same load during sampling. This is typically achieved by taking the sample during the idle periods when the current consumption is at its lowest. If you run the ADC and possibly the CPU during a RADIO TX event will increase the max. peak current and cause an even larger voltage dip, which may have a negative impact on your battery life.

    You can use Radio Notification Signals to find out when you want to do the ADC reading. Whether that is during RADIO TX, or in an idle period after the adv. event has ended is up to you.

    Best regards,

    Vidar

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  • 0

    Hello,

    I think the key is to have consistent readings, and to get that you have to make sure the battery has roughly the same load during sampling. This is typically achieved by taking the sample during the idle periods when the current consumption is at its lowest. If you run the ADC and possibly the CPU during a RADIO TX event will increase the max. peak current and cause an even larger voltage dip, which may have a negative impact on your battery life.

    You can use Radio Notification Signals to find out when you want to do the ADC reading. Whether that is during RADIO TX, or in an idle period after the adv. event has ended is up to you.

    Best regards,

    Vidar

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