Create heartbeat connection
The device serial port and the OBLOQ serial port may lose contact after a long time without data communication. By this command, the device and OBLOQ can maintain a certain frequency of data exchange.
2000 Set heartbeat data transmission frequency, unit: milliseconds, 2000 means by every 2 seconds OBLOQ will send data to the communication device.
-2 Negative number indicates that OBLOQ stops sending data.