Bluetooth SPP: Bluetooth SPP Pro (Android) vs. Microchip SmartData (iOS)

Question

All,

I am attempting to communicate, over an SPP profile, with an RN4678 Bluetooth chip connected to a microcontroller.

I never have a problem with the Android app. I can always pair (if not paired), connect, send messages to the chip, and disconnect. An example session is below:

%CONNECT,AB9876543210%
%RFCOMM_OPEN%
%TEST%    <-- Message sent using the keyboard ("Byte Stream Mode" option)
%RFCOMM_CLOSE%
%DISCONN%

With the iOS app, I can always pair (if not paired), connect, and disconnect. However, if I cannot send a message to the chip. An example session is below:

%LCONNECT,499B107AB1B5,1%
%LSECURED%
            <-- Here I try to send a message, but it is never received
%DISCONN%

The funny thing is that if I first connect/disconnect using the Android, and then I connect using the iPhone/iPad, reception is successful !!!!

%LCONNECT,499B107AB1B5,1%
%LSECURED%
%TEST%      <-- Yeah !!! Microcontroller receives the message
%DISCONN%

As far as I know, that path for the processing is the same ... In other words:

if(msg equals "RFCOMM_OPEN" or msg equals "LSECURED")
   go to state that monitors incoming messages

I, therefore, kindly ask the following:

1 - Have you encountered anything similar? Do you have any hints? What could the Android App possibly do that the iPhone app is not doing? What am I overlooking or not understanding?

2 - Are you aware of an app that works for both iOS and Android? What I mean, designed by the SAME guy/company?

If you need more info, please ask. I simply did not want to be too 'verbose'.

Thank you for your assistance.

Sincerely, Vincenzo

So ... I have been doing some additional reading ... It appears that the Bluetooth chip provides a service called "Transparent UART" ... If the service is active, the microcontroller would/should receive the following status message: LSTREAM_OPEN (which means that the BLE UART Transparent stream is currently open and data can be exchanged). I am now looking into why the stream is NOT open ... I am not sure if the necessary changes need to be on the Bluetooth IC or the iOS app or both -- We'll see ... — vpappano

vpappano vpappano · Accepted Answer · 2017-07-22T17:24:05

All,

At my job we have been playing with two RN modules: the RN4677 (we started with this module) and the RN4678.

The module allows the user to enter (and exit) a command mode. The RN4677 allows bidirectional communication with a manager while still in command mode. The RN4678 does NOT allow bidirectional communication with a manager while still in command mode.

All I needed to do was exit command mode (by issuing the command '---\r'). Now both modules work with Windows/Android/iOS ...

To summarize:

command "$$$\r" to enter command mode
various commands, requests for settings, ...
command "---\r" to exit command mode (a must for RN4678)

Everything will now work fine for both modules

I must say ... that was painful to troubleshoot ...

Sincerely,

Vincenzo

Bluetooth SPP: Bluetooth SPP Pro (Android) vs. Microchip SmartData (iOS)

1 Answers