Use a cellular and GPS SiP to implement asset tracking for agriculture and smart cities
additional parts beyond decoupling components, antennas, and those needed for separate matching networks for GPS and LTE antennas (Figure 6). Developers can easily combine the nRF9160 SiP with a Bluetooth device, such as Nordic Semiconductor’s NRF52840 Bluetooth wireless microcontroller and sensors, to implement a sophisticated sensor-based GPS enabled cellular asset tracker that provides users with access to data through their smartphones and other Bluetooth enabled mobile devices. Nordic Semiconductor further helps developers quickly begin evaluating cellular-based designs through a pair of development kits. For rapid prototyping of sensor- based asset tracking applications, the Nordic Semiconductor NRF6943 THINGY:91 cellular IoT development kit provides a complete battery-powered sensor
system that pairs the nRF9160 SiP with an NRF52840 Bluetooth device, multiple sensors, basic user interface components, a 1400 milliamp-hour (mAh) rechargeable battery, and a SIM card to allow out-of-the-box cellular connectivity (Figure 7). For custom development, the Nordic Semiconductor NRF9160- DK kit serves as an immediate development platform and reference for new designs. Although it does not include sensors like the THINGY:91, the NRF9160-DK kit combines an nRF9160 SiP with an NRF52840 Bluetooth device and includes a SIM card along with multiple connectors including a SEGGER J-Link debugger interface (Figure 8). For software development of an asset tracking application, Nordic includes a complete nRF9160 asset tracking application with its nRF Connect software development kit (SDK). The SDK combines Nordic’s nrfxlib software library for its SoCs, a Nordic fork of the Zephyr Project real-time operating system (RTOS) for resource constrained devices, and a Nordic fork of the MCUboot project secure bootloader. The THINGY:91 and NRF9160-DK kits come preloaded with the asset tracking application designed to connect with Nordic’s own nRF Cloud IoT platform. Using the preconfigured settings with either kit, developers can immediately
Figure 4: The nRF9160 SiP’s modem supports extended discontinuous reception which allows devices to achieve dramatic power savings by sleeping for a period of time negotiated with the cellular network. Image source: Nordic Semiconductor
eDRX
Figure 6: Using the Nordic Semiconductor nRF9160 SiP, developers need few additional components to
Up to 40- minutes vs. today’s upper limit of 2.56 seconds
implement the hardware design for a complete cellular-based asset tracker or other IoT device. Image source: Nordic Semiconductor
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power consumption. When in its unreachable stage with PSM, the device consumes only 2.7 μA. eDRX uses only slightly more current, consuming 18 μA in Cat-M1 operation or 37 μA in Cat-NB1 operation while using cycles of 82.91 seconds. Developing low power asset tracking solutions Implementing the hardware design for an asset tracking device based on the nRF9160 SiP requires few
execute a reattachment procedure that consumes an incremental amount of power. During long-term operation of a battery-powered device, this repeated small consumption of power can exhaust or significantly reduce battery charge. A device enables PSM by providing the network with a set of timer values that indicate when it will periodically become available and how long it will remain reachable before returning to sleep mode (Figure 5). Because of the PSM negotiation, the carrier network does not detach the device. In fact, the device can wake at any time and resume communications. The benefit is that it uses its low power sleep mode when it has nothing to communicate without losing its ability to wake as needed and instantly communicate. The nRF9160 SiP supports both eDRX and PSM, enabling the device to maintain operation with minimal
Figure 7: The Nordic Semiconductor NRF6943 THINGY:91 cellular IoT development kit provides a complete platform for rapidly prototyping sensor-based applications with both cellular and Bluetooth connectivity. Image source: Nordic Semiconductor
Figure 5: The cellular PSM protocol allows devices to take advantage of low power sleep modes without incurring the power costs of reattachment by negotiating specific periods when they are not reachable. Image source: Nordic Semiconductor
begin evaluating cellular-based asset tracking and prototyping their own applications. Along with the preloaded firmware, Nordic provides complete source code for the asset tracking application. By examining this code, developers can gain a deeper understanding of the NRF9160 SiP’s capabilities, and its use in supporting GPS localization and
LTE-M/NB-IoT connectivity in an asset tracking application. The main routine in this sample software illustrates basic design patterns for implementing a custom asset tracking application. When started, the main routine invokes a series of initialization routines. Among those routines,
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