St tips for low-power Bluetooth selection

In recent years, the rise of the Internet of Things has led more and more companies to choose wireless interconnection products. In wireless interconnection, low-power Bluetooth (BLE) is an indispensable product to support interconnection, because low-power Bluetooth does not need The gateway can communicate directly with the intelligent terminal, and has a better human-computer interaction experience, especially the Bluetooth MESH release, which allows more nodes to communicate on the same network.

Since many engineers have not had the opportunity to contact low-power Bluetooth products before, it is not clear how to choose. In this article, I will introduce the low-power Bluetooth model to ST.

ST has three low-power Bluetooth chips, all of which can be On the download, recently ST's low-power RF products also launched a Chinese forum: http://club.digiic.com/Forum/PostIndex?SectionID=34 , friends in need can go and see.

BlueNRG-MSQTR/MSCSP, BlueNRG-132/134, BlueNRG-232/234/248

Now let's take a look at the low-power Bluetooth selection from the following four aspects:

First, the program structure

First of all, we have to confirm that we choose MCU+BLE transceiver, MCU + Network processor or SOC solution.

In the MCU part of the SOC selection, we need to know the RAM, FLASH, GPIO, MCU core and the main frequency. In the Bluetooth part, we need to understand the power consumption, output power, receiving sensitivity, and Bluetooth protocol version.

Second, power consumption

The power consumption of Bluetooth low energy needs to be considered in the following five aspects:

1. Standby current, BlueNRG-1/2 is 0.9uA;

2. Real-time transceiver current, BlueNRG-1/2 RX 7.7mA, TX 8.3mA @0dBm.

3. Broadcast current (Bluetooth device does slave), which is related to the length of the broadcast byte, the time interval and the broadcast channel;

4. Scanning current (Bluetooth device is the master), this is related to the scanning window time and time interval;

5. Connection time, which is related to Payload and connection time interval.

If you use ST's products, ST will provide the BlueNRG Current Consumption Estimation Tool V1.4 tool, which provides all the current data described above, please refer to the picture below.

Third, the output power and receiving sensitivity

Everyone knows that the output power, receiving sensitivity and transmission distance are related. At present, the low-power Bluetooth specification stipulates that the low-power Bluetooth chip output power is less than 10dBm, and the receiving sensitivity is less than -70dBm. In real life, low-power Bluetooth is mainly used for data transmission with mobile phones, and most applications require transmission distances of several meters. For such applications, the receiving sensitivity and output power of low-power Bluetooth chips are not too much concerned. . In addition to Bluetooth, other 2.4G band WIFI, Zigbee, 2.4G products are also particularly large, and now the noise of 2.4G band is close to 20dBm, so in the case of other 2.4G devices, the selection sensitivity is not too concerned about the receiving sensitivity of Bluetooth. .

Fourth, low power Bluetooth protocol version

Currently, the low-power Bluetooth protocol has been upgraded from the original BLE4.0 to BLE5.0. For the main differences, please refer to the table below.

Finally, attach the ST low-power Bluetooth selection parameter list:

(*) Although BlueNRG-2 does not currently support all BLE5.0 features, it is a low-power Bluetooth chip that supports BLE5.0.