Specifications

HM-BT4502 V1.0
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EN switch of FFE4 channel is turned on, a notification will be generated in the
channel after the legitimate data sent by the main CPU to the module RX
through the serial port. APP can process and used it directly in the callback
function. Details see the chapter of Serial Pass-through Protocol Description
(Bridging Mode).
10.2 Anti-hijacking Key【Service UUID：0xFFC0】
The module supports anti-hijacking encryption. This service can effectively
prevent unauthorized mobile devices (mobile phones) from connecting to this
module. The initial password of the module is 000000 (ASCII). In this case, the
APP does not need to input the password. It is considered password less. Any
mobile device installing the specified APP can connect the module. APP can
set a new password (not all 0) and save it. If the new password (not all 0) is set,
the anti-hijacking password will be enabled. After APP connects this module, it
must input the new password once to the module within 20 seconds, otherwise
the module will disconnect. Before APP submits the correct password to the
module, no write operation can be performed in the service channel except
submitting the password. If users want to restore the password, they need to
reset the module first. For the security, the module does not provide password
read operation, and the memory of password is responsible for by APP. The
protocol provides a password channel to submit, modify and cancel the
password. It also provides the password event notification service to inform the