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Tag Low Power Analysis
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- Written by: zhang
- Category: Technology
Tag Low Power Analysis
This is a document from our development process.
After trying hard, when the tag entering sleep state, the lowest current is 15.x uA.
Let's analyze the possible power consumption areas.
ADC voltage dividing resistor
Two 1M resistors are used to divide the voltage to perform ADC on the battery 3.3V~4.2V.
This voltage divider circuit consumes 1.65 uA ~ 2.1 uA
XC6206P332 LDO
XC6206P332 is responsible for converting the battery voltage to 3.3V
The typical power consumption described on the Datasheet is 1uA , with a maximum of 3uA .
Capacitor leakage
Looking at the Datasheet of Samsung capacitors, the resistance at both ends is usually around 100MOhm. For a 3.3V power supply, the leakage current is equivalent to 3.3/100 uA, which can be almost ignored.
BAV70 charging part diode
In the charging part, BAV70 provides one-way communication. The manual says that at 25V, the reverse current is 40 nA
It can also be ignored.
Document Download
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- Written by: zhang
- Category: Technology
Document Download
Here are some technical information that you can download and study to have a deeper understanding of our products.
Hardware Design of Location Anchor
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- Written by: zhang
- Category: Technology
Hardware Design of Location Anchor
The main control of the location anchor is STM32F103RET6. This MCU has a relatively large Flash and a relatively large RAM, and is suitable for running RTOS.
The UWB transceiver of the anchor uses the DW1000 chip. We directly used the DWM1000 module in the early stage, because the DWM1000 module has already completed the radio frequency part and provides some SPI interfaces to the outside world. We do not need to worry about the analog part of the circuit and can just focus on the logic circuit. Later, some anchor types were added, and some changes were made in this part. Several new designs were added: (1) Making your own modules similar to DWM1000 can save costs; (2) Your own UWB modules use ceramic antennas or PCB antennas, and there are also IPX The base lead uses an external high-gain underline; (3) Add PA/LNA. The original communication distance can reach up to 300 meters at the rate of 850K, and it can reach more than 1000 meters after adding PA/LNA.
RTLE(RealTime Location Engine) Design
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- Written by: zhang
- Category: Technology
RTLE(RealTime Location Engine) Design
The location engine is the most important part of the entire location system. It is responsible for receiving data packets from each anchor and calculating the coordinates of the tag.
For the initial version, we developed it in Java. Later, it needed to be sold as a product. Java lacked sufficient security measures and could easily be decompiled. Our intellectual property rights could not be protected. Therefore, we changed to rewrite the location engine in C++. Because our customers basically use Windows servers, the location engine currently only has the Windows version. At the beginning of the design, we considered cross-platform and considered support for Linux in some important places. In fact, when the C++ version of the location engine was first written, we successfully compiled a Linux version and ran it on Ubuntu.
We need to continuously improve the engine, add functions, or improve ease of use. Customers basically have no demand for Linux, so we no longer pay attention to Linux support. If you have this need, it should be easiest to adapt the location engine to Linux.
The core of the location engine is the calculation of coordinates. We studied several algorithms, and by default, the least squares method is used for calculations. This algorithm is fast and highly accurate.
The location engine interface supports 5 methods: TCP binary message interface, RESTful style interface, TCP text message interface, TCP custom binary message interface, and serial text message interface.
Because UWB is defined as near field communication, this means that the coverage range of UWB will be very small. In particular, the radio management department has restrictions on the signal strength of UWB sending equipment. If the equipment is to be compliant, the coverage will be very small. In addition, some environments that require location are more complex, such as obstructions such as walls. In short, we need to support multi-region location, divide a large venue into multiple location areas, and deploy location anchors in each location area. These small location areas are combined to form a complete location area.
Our location engine supports multi-region location. For example, under normal circumstances, the range of each location area is 100 meters * 100 meters. The 400 meters * 400 meters area can be divided into 4 small areas in the shape of "田", which is equivalent to deploying "4 sets of location systems" . Of course, our system supports anchor reuse on regional boundaries. For example, if a anchor is deployed at the center of the word "田", all four regions can share this anchor. Deploying a anchor at each intersection of the word "田", with a total of 9 anchors, can achieve the effect of 4 anchors in each location area.
In practice, we found that there are fixed offsets in some places. To this end, we developed an algorithm to correct fixed offsets.
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