1. Background
In the process of low-frequency transmission of base stations, reducing power consumption through polling is an indispensable method. Although the method of constant transmission and constant reception can guarantee the quality of signal transmission and reception to the maximum extent, it is indeed a considerable expense in terms of battery consumption. Take the base station receiver NCK2910 as an example. When the constant reception is turned on, its power consumption can reach 11mA~12mA. The consumption of this module alone is enough to make battery capacity managers ashamed.
However, if a certain Polling mechanism such as "work-->low power consumption-->work-->low power consumption..." is adopted, the power consumption can be reduced to the uA level.
The time period of "working -> low power consumption" is called a polling cycle. We can roughly estimate the overall power consumption level based on the power consumption during "working" and the ratio of "working" to "working + low power consumption".
2. PJF7992 Transmitter Power Consumption Example
Let's take the power consumption of PJF7992 in the base station as an example. For low-frequency transmitters, the power consumption usually only needs to consider the time interval between transmissions and the current in the working state. Because the PKE commands of low-frequency transmitters are already defined in the protocol, there will not be too many changes. Therefore, if the protocol is determined, the time and structure of the corresponding PKE command will also be determined.
Taking the above command as an example, we can capture the current consumption of the "working" period of about 33ms through the corresponding device, which is 71.38mA (tested after the hardware matching work is completed). At the same time, according to the real-time captured data, it can be known that the power consumption of the device entering the low power state is about 68uA.
So if we send the PKE command every 2.1 seconds or so:
In the process of low-frequency transmission of base stations, reducing power consumption through polling is an indispensable method. Although the method of constant transmission and constant reception can guarantee the quality of signal transmission and reception to the maximum extent, it is indeed a considerable expense in terms of battery consumption. Take the base station receiver NCK2910 as an example. When the constant reception is turned on, its power consumption can reach 11mA~12mA. The consumption of this module alone is enough to make battery capacity managers ashamed.
However, if a certain Polling mechanism such as "work-->low power consumption-->work-->low power consumption..." is adopted, the power consumption can be reduced to the uA level.
The time period of "working -> low power consumption" is called a polling cycle. We can roughly estimate the overall power consumption level based on the power consumption during "working" and the ratio of "working" to "working + low power consumption".
2. PJF7992 Transmitter Power Consumption Example
Let's take the power consumption of PJF7992 in the base station as an example. For low-frequency transmitters, the power consumption usually only needs to consider the time interval between transmissions and the current in the working state. Because the PKE commands of low-frequency transmitters are already defined in the protocol, there will not be too many changes. Therefore, if the protocol is determined, the time and structure of the corresponding PKE command will also be determined.
Taking the above command as an example, we can capture the current consumption of the "working" period of about 33ms through the corresponding device, which is 71.38mA (tested after the hardware matching work is completed). At the same time, according to the real-time captured data, it can be known that the power consumption of the device entering the low power state is about 68uA.
So if we send the PKE command every 2.1 seconds or so:
while(1)
{
OSIF_TimeDelay(100);/********************************************
* ABIC2 PKE Transponder
*********************************************/
/* ABIC2 start up */
ABIC2_Start_Up( 0x10 ); // Low pulse duration T0, MPW is 0: T0 is controlled by DIN in transparent mode
ABIC2_PKE_Transponder( KeyIDE );
OSIF_TimeDelay(2000);
}
Then, the overall current consumption will be (working current * working time / polling time) + (low power current * low power time / polling time) = (71.38mA * 0.033ms / (0.033ms + 2.1ms)) + (0.06814mA * 2.1ms / (0.033ms + 2.1ms)) ≈ 1.17mA. The test results are not much different from the formula: 
We can temporarily ignore the relatively low low power consumption current, and simply calculate the maximum duration of Polling by the ratio of "working"/"working + low power consumption". As we know from the PJF7992 specification, the maximum power supply current of PJF7992 is 7mA, that is, the antenna driver is turned on for 33ms to send data. To reduce 70mA to 7mA, a 1:10 fast Polling is required, and the overall time must be extended to 330ms, that is, the polling time interval is not less than 300ms, otherwise the power consumption will be further increased.
The polling time setting of the low-frequency transmitter at the base station roughly follows this rule; the setting of the base station reception is actually similar to it, except that the receiver also needs to consider the actual reception effect and ensure that multiple frames of data are received, which will lead to the working time and low power consumption time being roughly determined after the protocol is determined. This also tells us that at the beginning, the formulation of the protocol (such as the number of bits of the wake-up code, the size of the data rate, the detection mechanism of the validity and failure of the wake-up code, etc.) is particularly important, so you can contact the WPI related window for more information on the specific mechanism.
Through the above explanation, I believe you have a better understanding of the Polling time setting: the Polling time should not be too long, otherwise it will affect the actual data receiving and sending effect, and it should not be too short, otherwise the power consumption will be difficult to reduce. The specific setting should be determined in combination with your own application when formulating the protocol.
3. References
[1] f7992A_2015.pdf
[2] ds452211 - Product data sheet NCK2910AHN Lizard (1.1).pdf
[3] an454912 - Application Note - AN-SCA 1715 Advanced Receiver Configuration (1.2).pdf
[4] an480711 - Application Note - AN-SCA 1720 Mean Current Consumption Measurement (1.1).pdf
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