“First of all, let’s talk about what is a wireless serial port module? The wireless module is the software and hardware module that transmits data through radio signals, the serial port module is the software and hardware module that uses the serial port communication protocol to transmit data, and the wireless serial port module is the software and hardware module that uses the serial port protocol for radio communication. Group. Take the following products as an example to introduce how to choose a suitable wireless serial port module for your own needs.
First of all, let’s talk about what is a wireless serial port module? The wireless module is the software and hardware module that transmits data through radio signals, the serial port module is the software and hardware module that uses the serial port communication protocol to transmit data, and the wireless serial port module is the software and hardware module that uses the serial port protocol for radio communication. Group. Take the following products as an example to introduce how to choose a suitable wireless serial port module for your own needs.
1. Selection points of serial port module
1.1 Communication frequency
The communication frequency is the frequency of the radio waves radiated by the wireless module when it is working. The commonly used frequency of the wireless serial module can be roughly divided into 170MHz, 230MHz, 315MHz, 433MHz, 490MHz, 780MHz, 868MHz, 915MHz, 2.4GHz and so on. In the environment of use, it is more necessary to choose modules with different frequency points to avoid interference. At the same time, different frequency points also have different characteristics in communication. For example, the 170MHz module has a lower frequency and a longer wavelength, so in the signal Compared with 868MHz and 2.4GHz modules, it has better communication effect in terms of penetration and diffraction capabilities.
1.2 Chip Solution
The chip solution refers to the RF processing IC used in the wireless serial port module. Different chips have different characteristics. The commonly used ones are SX1278, SX1276, SX1212, SX1280 of “SEMTECH” company; SI4463, SI4438, SI4438 of “SILICON LABS” company SI4432; and TI’s CC1110, CC1101, CC1310, etc. These chips have different characteristics, and modules using different chip solutions also have their own characteristics in RF communication. For our users’ selection, we can roughly estimate the performance differences and differences between modules from here. price.
1.3 Communication distance
The communication distance is also one of the core parameters of the wireless module. We choose the appropriate module according to the communication distance requirements we use. Because the wireless communication is affected by the environment and other factors, we need to pay attention to the need to reserve in the process of module selection. A certain distance, such as I need to pass 500 meters, then it is best not to choose a module with an indicator of 500 meters, at least choose a module above 600 meters, so that there is room to deal with environmental impacts, which also ensures the adaptability of the product and stability, etc.
1.4 Transmit power, receive sensitivity
So what is transmit power? The transmit power is used to indicate the ability of the radio frequency module to radiate radio waves. The transmit power of the wireless serial port module also indicates the ability of the module to radiate radio waves. The greater the transmit power of the module, the greater the communication distance will be under the same conditions. It has improved, but its power consumption will also increase, which requires more evaluation of the products made by yourself. So what is receiving sensitivity? The receiving sensitivity and the transmitting power correspond to each other. The transmitting power represents the external radiation capability of the module, that is, the transmitting performance. The receiving sensitivity represents the receiving capability of the wireless module. The sensitivity is usually represented by a negative value. It can be seen that the sensitivity corresponds to The smaller the value is, the better the receiving performance is. For example, the other parameters of the two modules are the same. The sensitivity of the No. 1 module is -120dBm, and the sensitivity of the No. 2 module is -126dBm, which means that the receiving performance of the No. 2 module is better. Don’t underestimate the 6dBm gap. In theory, this can make the communication distance of the No. 2 module twice as far as that of the No. 1 module.
1.5 Transmit Current, Receive Current, Sleep Current
The emission current refers to the power supply current required by the module when transmitting. This parameter is also very important for our selection, because some products can provide a small amount of power, such as wearable devices, so you need to pay attention when choosing a module. For this parameter, the power supply capacity of the power supply is usually at least 1.3 times the emission current. The receiving current is the working current of the module in the normal receiving state, and the dormant current is the working current when most of the functions of the module are not used. This parameter is very important for users who make low-power products.
1.6 Air rate
The air rate here refers to the rate at which the radio frequency signal of the wireless module transmits signals in the air. The air speed is related to the amount of data transmitted by the wireless module. The higher the air rate, the larger the amount of data that the wireless module can transmit per second. For example, the remote control of the drone needs to have a high airspeed to ensure the transmission of a large amount of data to control the flight. The higher the airspeed, the smaller the delay of wireless transmission. Of course, the choice and setting of the airspeed are not absolute, the greater the more suitable for us to use, this depends on the situation of our own products, and the airspeed The higher the communication distance to the module will also lead to a certain degree of shortening, which also needs to be considered in combination with distance conditions, data volume, real-time performance and other issues.
1.7 Antenna interface form
Before the antenna, I also have an article about the influence of the antenna on the communication distance of the wireless module. The antenna gain is also very important for the wireless communication system. Therefore, the selection of the module should also consider the form of its antenna interface. The commonly used interfaces are roughly divided into SMA and IPEX. Some modules also have an on-board PCB antenna, which is what we need to pay attention to when choosing products. The on-board PCB antenna has the advantages of small size and easy integration, but its communication distance is short, and the antenna of SMA and IPEX interface is in the gain. The volume and other aspects are larger than that of the PCB.
1.8 Package form and size
Package and size refer to the mechanical geometric size of the module, and this indicator needs to be comprehensively considered in combination with the size and space requirements of its own products. The package of the module can be roughly divided into two types: in-line and patch.
2. And give examples to illustrate the selection points
The following three tables are used as examples to illustrate the selection method of wireless modules:
The three meters we often say are gas meters, electricity meters, and water meters. The application of wireless meter reading in life is also very extensive. What should we pay attention to when choosing wireless modules among the three meters? First of all, wireless meter reading does not have high requirements on the amount of data transmitted by the module, and the requirements on the real-time performance of the module do not need to be too high. Therefore, from these two points, the selection of wireless modules does not require high airspeed. Secondly, in the application of three meters, we have certain requirements for the penetration and diffraction performance of the module, such as 433MHz, 490MHz, etc., because they are all house buildings. Then in the three tables, the power consumption of the wireless module cannot be too high, so it is necessary to select a module with appropriate power consumption. The volume restrictions of the last three tables are mostly not high, so it can be considered comprehensively. Taking the module of Chengdu Ebyte as an example, the module of the E32 series is more suitable.
In general, the selection of wireless modules is a comprehensive problem that we need to consider according to the performance requirements and design dimensions of our own products. Finally, I hope this article will help you to choose a suitable module.