Warehouse positioning system based on sx1280 chip

Due to poor indoor signal, GPS cannot be used for indoor positioning. However, the demand for indoor positioning is wide, and many applications need to locate the position of people or objects in the indoor space, especially warehouse management.

TOF ranging is a algorithm of Radio frequency (rf) positioning, which belongs to the two-way ranging technology, it uses the data signals on the flight time between tramsmitter and receiver to measure the distance between two points.

Measurement steps:

1. Measure the time interval between the master sending the data signal and receiving the slave response signal, note as Tt.

2. Measure the time interval between the slave receiving the data signal from the master and sending the response signal,note as Tr.

3. The one-way flight time for the signal between the master and slave:Tf=(Tt-Tr)/2.the distance between the two points: d=c*Tf, c represents the electromagnetic wave propagation speed.

SX1280 is a 2.4G range-finding chip based on LoRa modulation newly launched by semtech. In addition to the commonly used wireless communication functions, SX1280 also integrates TOF (time-of-flight) ranging function.

Advantage:

The algorithm has been integrated in the chip, and the ranging results can be obtained with simple operations, which can be used for users to quickly realize indoor positioning.

Implementation plan:

This algorithm needs at least 5 wireless modules with SX1280 chip，it require one center, three base stations and at least one positioning module.

◆ The center is responsible for receiving and counting the distance information of the positioning module and uploading it to the server.

◆ The three base stations used as slaves in the ranging, they need to be installed evenly in the warehouse for the positioning module to calculate the distance.

◆ The positioning module is installed on the goods that to be located, center measure the distances between the three base stations separately (ranging status), and upload these three distances to the center (communication status).

Specific steps are as follows:

1. The positioning module is in the receiving state.

2. The center sends the instruction that obtain positioning information to the positioning module.

3. The positioning module switches to the ranging state.

4. The positioning module measures the distance with base station 1, and obtains the distance d1.

5. The positioning module measures the distance with base station 2, and obtains the distance d2.

6. The positioning module measures the distance with the base station 3, and obtains the distance d3.

7. The positioning module switches to the communication state.

8. The positioning module uploads d1, d2, d3 to the center.

9. The center uploads d1, d2, and d3 to the server.