SPLatco Knowledge Base

BT-RS232 Bluetooth adaptor

The BT-RS232 adds Bluetooth serial communications to your compatible SPLat controller. It works with any SPLat controller that has suitable firmware and a 9-pin programming connector using RS232 voltage levels. This includes SL100, MMI202 and custom controllers. It is not suitable for controllers that use 3.3V or 5V levels. If in doubt about your controller, please contact us.

This instruction assumes you are using the BT-RS232 to connect a SPLat controller to an Android device. The BT-RS232 is a slave-only device using Bluetooth Serial Port Protocol (SPP).

Do not rely on Bluetooth communications to maintain the safety of a system. It does not provide a secure connection.
Installation

The BT-RS232 simply plugs onto the controller’s 9-pin DB9 programming connector.

Communications parameters

The adaptor is factory pre-set to 38,400 baud, 8 data bits, no parity.

Power supply considerations

The BT-RS232 draws its 5V power from the programming connector. It will draw more current off the controller than the controller was initially designed for (after all, we designed the controllers long before a Bluetooth adaptor was contemplated). In most cases this will fall within the conservative design of our controllers, especially at temperatures below the maximum rated for the controllers (normally 60°C). At high temperatures there is a slight chance that the regulator on the controller will shut down on thermal overload (the controller will stop working but recover when it cools down). We suggest you consider that the use of external adaptors on standard SPLat controllers is for Proof of Concept work. If you want to deploy them in your product on an ongoing basis please either consult us with your specific operating conditions, or consider a custom SPLat that has been designed for the purpose.

Radio propagation, range

The BT-RS232 is Class 2 Bluetooth, which has a range of up to 10m in free air, line of sight. The “snake” pattern on the end of the board is the antenna. This needs to be kept away from any metal surfaces, and the whole unit should not be enclosed in metal.

You can maximise the range by making sure the adaptor is in an elevated position, clear of any surrounding metal. You can use up to 20cm of extension cable.