Review on 🔌 2pcs HC-05 Bluetooth Wireless RF Transceiver Module for Arduino - Master and Slave Mode (2pcs, HC-05) by Fisseha Rodgers

Although you can search google for several tests and find conflicting information on whether the device defaults to 38400 baud or 9600 baud in non-AT mode, there is no suitable description. Nowhere can you read a table what the blinking red light on the module indicates (it has at least 4 modes and I mentioned 2 modes in the articles). After several hours of trying, I was able to get into the AT interface via the Arduino board and select all of the module's internal settings. You must have the correct line termination to even enter. I eventually found that both devices were configured to communicate over Bluetooth at 9600 baud with no stop or parity bits. Every communication device seems to be looking for a stop bit, not a zero. This resulted in a refusal of communication. If you like solving puzzles, this is a great product. I upgraded it from 2 to 3 stars as it's pretty reliable when it works. Note that I can connect it to an old Samsung Galaxy using the Bluetooth Terminal app and pair it with a TP-Link Bluetooth dongle on my desktop. My iPhone 8P flatly refuses to see the HC-05.