A MiWi to Bluetooth Bridge

 

To control the train system I used the Zena Wireless Adapter, pictured below from Microchip.  The Zena has a PIC18F27J53 and the MRF24J40 MiWi transceiver.  I actually opened it up and reprogrammed it so it would handle by higher level protocols.  One big downside is even with a USB Bootloader, you still have to open it up.  Also I am constantly misplacing it, since it is just a USB dongle.



I also would like to use the Tablet/Phone to control the trains.  This means either a MiWi-Wifi bridge or a MiWi-Bluetooth bridge.  I bought the Microchip developers kit for the Wifi bridge, but I have never figured out to do these micro web servers, etc.  With Bluetooth I have extensive libraries, since I use it for quite a few of my little modules.  So the picture at the top of this post is the answer.  This PCB will be mounted on the edge of the train layout so that I can connect a USB cable when needed.

What is it?

The design is quite simple,  A 2" x 4" 2 layer board that is everything the Zena is plus a BT module and some LED power.  Since you cant buy MRF24J40MA modules until late 2022/early 2023, I decide to go a slightly different route.  I can buy the Mikro Bus CLICK versions (https://www.mikroe.com/mikrobus).  On some level just plugging in a module is appealing,  I did violated the Mikro Bus spec by only connecting the lines I need and in my configuration.  But the configuration seems to be the same for all the MiWi and BT Click modules.  Thus you will be able to use this PCB to build a bridge between any MiWi module (2.4GHz, 900Mhz and 315Mhz) and any BT device that a CLICK module exists for. 

This design has a DC-DC converter that converts the 16VAC to 5VDC @ 1A+, but is good up to 24VAC input.  The processor and the radios use about 50mA, so the rest is dedicated to lighting power.  I added a SPI EEPROM for storing configuration information. Finally there is a 5VDC switch that will be used for 5VDC LED lighting, using the left Red/White connector.  There is about 800mA+ of excess power.

This one is supposed to be white with black silkscreen, the color rendered did not quite do white, it was 255, 255, 255 though.