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This article mainly introduces "Android BLE how to achieve code sweep gun based on BLESSED development". In daily operation, I believe that many people have doubts about how to achieve code sweep gun based on BLESSED development in Android BLE. Xiaobian consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful for you to answer the doubt that "Android BLE how to achieve code sweep gun development based on BLESSED". Next, please follow the editor to study!

1. Bluetooth mode HID and BLE

When the code sweep gun is connected to the mobile phone, the Bluetooth HID (Human Interface Device) mode is usually used. In essence, it uses the code sweep gun as a hardware keyboard and inputs the results of the scan code into the corresponding control one by one according to the keyboard protocol.

Advantages: pairing can be used as keyboard input immediately without the need to develop integration. You can use components such as input boxes to receive the scan results directly.

Disadvantages: poor support for non-numbers, related to input method, English association will be triggered at some time-_ |, conflict with virtual keyboard, you need to switch keyboard input method when connecting code sweep gun.

The tags we want to scan are not only English, special symbols, but also Chinese, so the Bluetooth code scanning gun accessed in HID mode can not meet the requirements in the end. So the code sweep gun which supports BLE mode is re-selected.

BLE mode code sweep gun

Advantages: good compatibility, follow Bluetooth protocol, has nothing to do with keyboard input method. At the lower level, the original binary data stream is returned directly to facilitate the determination of coding and character coding conversion.

Disadvantages: need to carry out native development, deal with device scanning, connection, data reading and writing and other operations.

II. Vernacular of BLE agreement

Fortunately, there is github, in which the BLESSED for Android-BLE made easy project is an open source library dedicated to simplifying BLE development on android. However, it is necessary to briefly understand the main concepts of the BLE protocol before writing the code.

The two more important things are Service and Characteristic. In short, a device can provide multiple services, each service can provide multiple feature functions, and each service and feature corresponds to a UUID.

Communication with the device is carried out through functions, each of which is indicated by Properties (attribute) that the feature supports read, write, or notification.

To make it easier to understand the BLE protocol, it is recommended to download an APP called "BLE debugging Assistant". Here is a screenshot of APP.

The screenshot shows how to read power from a device that supports the BLE protocol without pairing in advance. After opening APP to scan to the corresponding device, click Connect, and then list a bunch of Service (services) mentioned above. Those that can display the service name, such as "Battery Service", are obtained in accordance with the agreement of UUID.

If the battery service is 0x180F. After clicking on the service, there is Characteristic, where the Properties of Battery Level (also the UUID convention 0x2A19) is READ NOTIFY, indicating that this feature supports reading and notification.

Click the down arrow, click read, and show that the returned data is 0x5D (decimal estimate more than ninety:-0).

Battery service is a standard service stipulated in the agreement, but the code sweeper does not seem to be. We also need to find which Service and which Characteristic to notify after scanning the code, and it is not difficult to find APP through this tool. Note, open the notification data.

After scanning the code, the data will be displayed, and after you find it, you can start coding.

Third, the use of the third-party library BLESSED for Android

Https://github.com/weliem/blessed-android

Let's move on to the specific chapter code.

Install gradle file to join

Allprojects {repositories {... Maven {url 'https://jitpack.io'}} dependencies {implementation' com.github.weliem:blessed-android:2.0.6'

Scanning equipment

BluetoothCentralManager central = new BluetoothCentralManager (AppContext.baseAppContext, bluetoothCentralManagerCallback, new Handler (Looper.getMainLooper (); central.scanForPeripherals ()

BluetoothCentralManagerCallback is a scan callback method, and there are three important ones

/ / found a device @ Overridepublic void onDiscoveredPeripheral (BluetoothPeripheral peripheral, ScanResult scanResult) / / connected device @ Overridepublic void onConnectedPeripheral (BluetoothPeripheral peripheral) / / device disconnected @ Overridepublic void onDisconnectedPeripheral (BluetoothPeripheral peripheral, HciStatus status)

After the device is found, onDiscoveredPeripheral, connect the device, and stop scanning. BluetoothPeripheralCallback is a device callback and is used to accept notifications.

Central.autoConnectPeripheral (peripheral, bluetoothPeripheralCallback); central.stopScan ()

Query the services and features provided after onConnectedPeripheral connection

Log.i ("BLE", "onConnectedPeripheral"); List serviceList = peripheral.getServices (); for (int I = 0; I < serviceList.size (); iTunes +) {Log.i ("BLE", "Service:" + serviceList.get (I). GetUuid ()); if (serviceList.get (I). GetUuid (). ToString (). Equals ("6e400001-b5a3-f393-e0a9-e50e24dcca9e")) {List list= serviceList.get (I). GetCharacteristics () For (int j = 0; j < list.size ()) {Log.i ("BLE", "Characteristic:" + list.get (j). GetUuid ());}

After onConnectedPeripheral, the notification is enabled for the feature, and the UUID of the service and the feature need to be filled in. The scan result is returned with notification information.

BluetoothGattCharacteristic currentTimeCharacteristic = peripheral.getCharacteristic (SERVICE_UUID, CURRENT_TIME_CHARACTERISTIC_UUID); if (currentTimeCharacteristic! = null) {/ / enable notification peripheral.setNotify (currentTimeCharacteristic, true);} / / create binding boolean bret= peripheral.createBond () to communicate with the device

Disconnecting and reconnecting can be handled in onDisconnectedPeripheral

The receiving scan result is processed in the following method in the device callback class bluetoothPeripheralCallback. Where value is the QR code value scanned.

@ Overridepublic void onCharacteristicUpdate (@ NonNull BluetoothPeripheral peripheral, @ NonNull byte [] value, @ NonNull BluetoothGattCharacteristic characteristic, @ NonNull GattStatus status)

In addition:

The Chinese code is usually GBK or UTF8, which requires guessing and judgment. Finally, a tool function is attached.

Because the default packet of BLE is short, a large amount of data will be split and sent many times, and onCharacteristicUpdate will be called many times. After the value is stitched together, the character coding will be judged.

Public static Boolean isUtf8 (byte [] buffer) {boolean isUtf8 = true; int end = buffer.length; for (int I = 0; I < end; iTunes +) {byte temp = buffer [I]; if ((temp & 0x80) = = 0) {/ / 0xxxxxxx continue } else if ((temp & 0xC0) = = 0xC0 & & (temp & 0x20) = 0) {/ / 110xxxxx 10xxxxxx if (I + 1 < end & & (buffer [I + 1] & 0x80) = = 0x80 & & (buffer [I + 1] & 0x40) = 0) {I = I + 1; continue }} else if ((temp & 0xE0) = = 0xE0 & & (temp & 0x10) = = 0) {/ / 1110xxxx 10xxxxxx 10xxxxxx if (I + 2 < end & & (buffer [I + 1] & 0x80) = = 0x80 & & (buffer [I + 1] & 0x40) = = 0 & (buffer [I + 2] & 0x80) = = 0x80 & & (buffer [I + 2] & 0x40) = = 0) {I = I + 2 } else if ((temp & 0xF0) = = 0xF0 & & (temp & 0x08) = = 0) {/ / 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx if (I + 3 < end & & (buffer [I + 1] & 0x80) = = 0x80 & & (buffer [I + 1] & 0x40) = = 0 & (buffer [I + 2] & 0x80) = = 0x80 & (buffer [I + 2]) & 0x40) = 0 & & (buffer [I + 3] & 0x80) = = 0x80 & & (buffer [I + 3] & 0x40) = 0) {I = I + 3 } isUtf8 = false; break;} return isUtf8;} at this point, the study on "how to implement code scanning gun based on BLESSED development by Android BLE" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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