ELAD Blueduo

BLUEDUO - remote operation of the FDMDUO SDR 

One of the programmers of the ELAD FDM_DUO SDR has worked with ELAD to create a very interesting application. This is called BLUEDUO and is a bluetooth connection to the  SDR which allows remote working. The only thing it does not provide is remote sound in or out... which I guess is due to the comms speed of Bluetooth being to low to handle both the tuning and spectrum data as well as audio.

The Blueduo software is a Google Android app available on the ELAD web site. To try it out I have

1. Begged and borrowed an Android tablet from my son - who has everything

2. Purchased a Bluetooth dongle, HC-05

3. Used a FT323 USB <-> Serial TX, RX dongle I already have to program the HC-05

4. Downloaded the software "apk" file from ELAD, and installed this on the tablet - for this you need to download it, use the tablet file manager and give permissions under settings to allow non-Google Play Store apps to be installed. But then it is just a matter to double clicking the downloaded file to install it.

5. Bought a DB9 male plug to connectors flat cable (There may be other sources, it was very difficult to find!)

BUT FIRST, PROGRAMMING THE HC-05

The FT232 pins connect to the HC-05 as follows

FT232  HC-05

GND -> GND

VCC -> VCC

RXD -> TXD

TXD -> RXD

The HC-05 has now to be programmed. Wire it up as listed above. 

When delivered the HC-05 dongles almost certainly come with their baud rate set to 9600 or 38400 baud. Connect the FT232 by USB to your computer - mine is an Apple MacBook. I use a serial terminal app called iSerialTerm which can select the USB port, select the speed 38400 and start a connection (There will be Windows terminal apps, but I don't know about them). Set the "Send" format to be your typed commands followed by a CR/LF (/r/n).

But first disconnect the HC-05 Vcc, press the small button and hold it down, then reconnect the Vcc to get into program mode. Showed as a slow flashing LED. 

Now check the HC-05 is responding by sending a command.

AT+VERSION?

to which it should respond with its version number. 

When you have a correct response enter the following commands - you may have to repeat entry to the program mode before each command is given - I did...

AT+NAME = BLUEDUO

AT+UART = 115200,0,0

AT+PSWD = 1234

This will set the Bluetooth dongle name to BLUEDUO, to a speed of 115200 baud required by the FDM-DUO and a Bluetooth password of 1234.

WIRE UP THE HC-05

Now you can remove the FT232 connections and make connections to the 9pin connector of the FD-DUO.

Pin side view

Check with a meter the pin to cable colours to find the correct connections to use. Mine were like this

HC-05   FDM-DUO (9pin)

GND      pin 5    WHITE

RXD      pin 6    RED

TXD      pin 7    YELLOW

Vcc      pin 9    GREY

Plug the 9pin into the radio. Use your Android Tablet and join the Bluetooth connection BLUEDUO and give the password 1234 you set above. Start the Blueduo app. And bingo a display of the spectrum and waterfall and lots of buttons to control the SDR.

Finished interface

LOOK AT THIS

FDM-DUO on 20m WSPR TX

USB Peak at -5dB, LSB at -65dB

One interesting point. When using the Blueduo display it not only shows the received spectrum but also your transmitted one. Where, for example on digital modes, you can see the transmit peak signal, but also to the side the other sideband up to 60dB down, and any high modulation harmonics USB which may indicate over modulation of the digital USB sound input.