I am looking at bringing the system power down to extend battery life. The power breakdown in idle mode is as follows:
|Component||Active RX Power||Sleep Power||Avg. Power||Notes|
|RFM69HCW||17mA||0.7uA||9mA||50% sleep duty cycle|
|Teensy LC||5mA||150uA||2.5mA||50% duty, w/ bootloader|
|Totals||22.16mA / 73.1mW||317uA / 1mW||11.66mA / 38.5mW|
The battery I have chosen has a capacity of 150mAh @ 3.7V. The system runs at 3.3V so energy rating of the batter at 3.3V is 150*(3.7/3.3) = 168mAh @ 3.3V. This means the standby time is 168/11.66 = 14.4 hours. That's a full day of standby time!!!
I think we can push the sleep duty cycle longer than 50% to save even more power. Probably by as much as 80% duty.
Now to measure the full system during streaming mode:
Here, I put the whole system into stream mode and measure the supply current (measured on the battery voltage rail).
|Mode||Power||Max Duration (based on 150mAh)|
|STREAM_RX||37mA @ 3.7V||4 hours of talk time|
|STREAM_TX (31 power setting)||39.6mA @ 3.7V||3.8 hours of talk time|
|STREAM_TX (15 power setting)||38.9mA @ 3.7V||3.85 hours of talk time|
|STREAM_TX (0 power setting)||38mA @ 3.7V||3.9 hours of talk time|
Wow, 4 hours of talk time! There must be something missing... there is, the speaker. The speaker driver can source as much as 120mA when driving a lout signal. Therefore The talk time is limited to more like 1 hour of receiving.
12+ hours of standby
1+ hour of talk time
Actually, not too far off from an old Nokia bar phone...