Application – converting a number of microchip PIC based plug-in analyzers, RS232 PC interface adapter (MAX 232), and USB adapter (CP2102) to Bluetooth transceiver such as Microchip RN42 series for smart phone display interface. All of the host embedded controllers are PIC 16C, 16F, or 18F having UART serial communication ports. The goal is maintaining the host controller communication or software as represented by examples A and B. There are 15 plus years of controllers in the field most of which are compatible with the three types of wired, plug-in remotes (B, D, E). Thus the new Bluetooth transceiver must interface with TTL 0-5V UART RX and UART TX. The connection has been a maximum of a 6 foot, 6-pin flat cable with a simple 0.1 pin connector at the host board. The new wireless Bluetooth 6-pin flat cable will probably be less 2 feet in length.
This is a single “terminal” application, there is no necessity for network, other communication, etc. The host controls the transmission link. The data packet length is quite short, essentially transferring fill-in data fields from the remote to the host or displaying a few data value monitors the host sends to the remote once every 3 seconds, independent operator modes.
Attached is a sketch of a simplified circuit, what is the proper component selection for the drivers, etc?
Background – from the attached schematics (probably A and B) we have had adequate experience and satisfactory performance with UART TTL 0-5 to UART TTL 0-5. As shown we’ve only used a couple of transistors and again it’s been working adequately.
However, with Bluetooth we are now faced with TTL voltage level shift and setting up the 3.3V rail for the RN42. If I am interpreting the SN74L*** series correctly there can be a buffer/driver arrangement to take care of this circuit (have data sheet SN74LVC2T45).
Thank you for taking the time to review this, after review feel free to give me a call for further clarification.6562.Blue Tooth Interface.pdf
