How much does the current consumption increase when measuring RSSI with the nRF52833?

[YUKIOOYAMA]

Hi all,

What is the increase in current consumption or power consumption when measuring RSSI with the nRF52833? 

My device is a peripheral. I would like to estimate this increase because it might affect our RSSI measurement frequency (and thus battery consumption).

If you do not have data for the nRF52833 but have data for other devices (such as the nRF52840), please share it with me for reference.

Best Regards,

YUKIOOYAMA

[Samruddhi Jadhav]

Hi,

The increase in current consumption for RSSI vs. "RX without RSSI" isn't specifically mentioned. You can assume here that the dominant cost is simply the time the radio spends in RX and enabling RSSI sampling does not add extra DC current component. For a more accurate value, you can measure your hardware with Radio in RX and no RX sampling. So, without calling RSSISTART. Then, measure with radio in RX and periodic RSSI sampling. So, with RSSISTART. To know the real overhead or RSSI cost of your design you find the difference between these two averages.

Best Regards,

Samruddhi

[YUKIOOYAMA]

Hello Samruddhi-san,

Although what you say is true, when looking at the current consumption during reception (only empty packets), I could not determine whether it was a measurement error or not.

You mentioned that the cost of RSSI measurement is mainly the measurement time, and the current consumption hardly changes. In other words, is the increase in power consumption only due to the measurement time?(i.e., mAh) 

Could you please tell me the specific duration of the RSSI measurement?

BR

YUKIOOYAMA

[Samruddhi Jadhav]

Hi,

Yes, you are correct. The power consumption increase is based on how much longer you keep your radio active to take the measurement in receive RX mode. I would suggest you to take a look at the nRF52833 specs docs. It is given that:

RSSISETTLE:15µs. This is how long you must wait after signal level change for the RSSI value to stabilize. 

RSSIPERIOD: 0.25µs. This is the time it takes for the sample to be captured after RSSISTART is triggered. 

If the radio is already receiving a packet, the RSSI measurement is basically "free" when it comes to battery. On the other hand, if the radio is off and you turn it on only to measure RSSI, you would have to account for the radio's RX current and time needed for the radio to get to Ready state. In that case, the cost would be usage of standard radio electricity multiplied by the waiting time.

Best regards,

Samruddhi

[YUKIOOYAMA]

Hello Samruddhi-san,

I found that it is a very short period of time. I also appreciate you showing me the spec sheet where it is written.

I understood that I don't need to worry much about obtaining the RSSI during the connection state.

My questions are now resolved, so I will close this case. Thank you for your support.

BR

YUKIOOYAMA