With help of Phillipe Cantin, Byron's Blog, arduino-info.wikispaces.com/BlueToothCommandUtility and Martyn Currey I managed to get my Bluetooth connection working. There were just 2 Arduinos connected, using HC05 Module.
Comparing to NRF24L01, it is more difficult.
It seems that power used ist double, distance increase may be just 10%.
However, what puzzles me, is that 20% of data volume is wrongly transmitted.
Test as follows:
I transmitted a 16 Bit Integer in a handshake protokoll.
Per transfer, the integer got increased by "1".
This runs fast an reliable, if I replaced the HC05 by some cable connection, from RX Arduino 1 to TX Arduino 2 and vice versa, no worries, all fine.
However, if I use the HC05 Modules, appox. 20% of data is wrongly transmitted.
Is there no error protection, check sum in the SPP protokoll?
What is your experience?
In my experience a lot of Bluetooth messages aren't received by the target device. If it's important for messages to be received I generally transmit the message several times and if no acknowledgement is received, I transmit the data again.
I'm not aware of any sort of automatic retries with Bluetooth so I use my own protocol.
I found my App Inventor 2 program became much more cumbersome when I added acknowledgements and retransmission. The plus side of this extra code is, unless an error message is displayed, I can be sure the message was received.
I have data reliability issues with HC-05/06s using any speed other than 9600 on software serial and anything above 38400 on hardware serial. If I need accurate data I use a very simple checksum.