At the beginning of the project (in 2012) their was 2 technical challenges to overcome concerning bluetooth : it was bluetooth 2.5 so it was impossible to connect with ios devices without MFI (too expensive for makers/scientists). In addition it was difficult to connect to desktop computer because the SPP (serial port over bluetooth) profile is not very stable (at least on windows) and it required to install a third party bluettoth stack (such as bluesoleil) or making a custom usb-serial-bluetooth converter.
Now with Bluetooth 4.0 + ble , the problem of mobile compatibility is solved but there is still a problem of connection with computers : BLE stack has not been implemented on every os and in order to connect a BLE device, a developer would have to develop an app for each OS using OS-specific frameworks.
For Movuino we didn't wanted to use this approach because developing, debugging and maintaining sofware for every OS would take too much time. So we chose to make custom dongle that do the ble to serial convertion and so for any os it appears as a generic serial port. The drawback to this approach is a higher production cost because instead of making one object , we have to make two.
* picture of the dongle -
The hardware files can be found in the Movuino github repository in the dongle folder.
The difficult part was to make the dongle connect automatically to the Movuino. For this we used the scripting language offered by bluegiga in their BLE112 modules.
This module will be replaced by a NRF51822 or NRF52832 in the next versions.