First test of Cricket Asset Tracker power usage described here. At 10 minute LoRaWAN and GNSS acquisition interval total power usage was ~2.1 mA. Next step is to make the GNSS wake up frequency motion dependent.
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Second Power test of the Cricket Asset Tracker completed yesterday.
In this test, I implemented the motion detect using the BMA280 accelerometer on board as described here.
The asset tracker was configured to read BME280 and VEML6040 sensor data and battery level every minute, log to the SPI flash every minute, send the latest data via LoRaWAN every ten minutes, and obtain a GNSS fix every hour unless the BMA280 detected motion, then the GNSS fix rate was once per minute. The GNSS fix was determined to be obtained once the EPE (estimated position error) fell below 100, then the CAM M8Q would go back to sleep until the next wake period.
EPE of 100 is rather low resolution for GNSS and the results were usually a cloud of points on the CayenneLPP map mostly covering my house with an occasional outlier or two, so not bad. But this needs to be tightened up for actual asset tracking.
The asset tracker spent most of the time sitting outside on my back deck table or inside on a window sill if it was raining (enclosure is not waterproof). Once a day on average I took the asset tracker for a walk to get the mail or down the block to make sure about once a day the “in-motion” threshold was triggered and extra GNSS fixes were required. This is to mimic the actual use case of tracking items that are expected to be stationary most of the time and where it is important to know when they are being moved as well as generally where they are.
Anyway, the test lasted 14 days 6 hours on a fully-charged 105 mAH 1S LiPo battery so average current of ~307 uA. This exceeds expectations since this means at this configuration and use rate the asset tracker would last about one year on a single 3.6 V, 2.6 AH Lithium Thionyl Chloride (AA-sized) battery.
Next test (just started) is to double the long-frequency duty cycle to two hours (ephemeris data grows stale after four hours) and halve the accuracy criterion to EPE = 50.
I will report on the results of this test in about two weeks.
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Hi,
I have one of your grasshopper boards (Arduino). I am struggling to find information on the pin numbers to use to trigger interrupts. Do you have any pointers, or even better, an example of could learn from?
Thanks in advance
Riccardo
Tindie might have been a better place to ask this question.
There is a Grasshopper schematic and pinout on the Tindie page. is this what you are asking for?
There are examples of how to use interrupts in the CMWX1ZZABZ github repository.