Archive for November, 2014

Allstar Nano Node Project

Saturday, November 29th, 2014

Allstar Nano Node Project

I am starting a new project for the Beagle Bone Black. This will use the DorJI DRA818U Transceiver module. This will be installed on a proto-cape board along with a modified audio FOB. The following sections will document this process. These will be my raw notes and I’ll clean them up depending upon the outcome of this project.

Thoughts

Dorji DRA818U Information

This module can be found on ebay and is very inexpensive.

Block Diagram of the DRA818U Module:

 Block Diagram of Module

Pin Functions:

Radio Characteristics:

Application Block:

Allstar Nano Node

I was able to get a prototype working on Allstar using the Arduino to program the module. I’ll be drafting up a diagram once I’ve worked out the issues and add some additional features.

I soldered resistor leads to the module. You can then bend the leads slightly to allow the module to be mounted on a standard proto-boards. Be careful the amount of heat that you use as you can damage them.

Next Version mounted on a BBB cape https://www.dropbox.com/s/n3d4uitmtk0l8mp/IMG_20141128_183736.jpg?dl=0

I am working on a program to setup the frequencies, volume and filtering from a usb/serial device. I have also discovered that these modules will save there frequency/setup information, so once it’s programmed, it will remember the settings when powered up. I originally thought that this was not the case with the DRA818u modules.

IMG_20141209_155808a

Above is the original proof of concept board. It uses a modified FOB, DC to DC power converter and the Dorji DRA818u module and is powered by the USB connection from a powered hub.

Additional Information

Here is some additional information regarding these modules DRA-818. There is a command called: AT+DMOCONNECT. Per the programming manual:

Handshake Command Description: It is used to check if the module works normally. DRA818U module will send back response information when it receives this command from the host. If the host doesn’t receive any response from module after three times of continuously sending this command, it will restart the module.

Format:

AT+DMOCONNECT <CR><LF>

Module response:

+DMOCONNECT: 0 <CR><LF>

One thing is that the document does not indicate is that the settings will be reset. This command is useful for checking the module, but after execution, the module will require to be re-programmed by resending the setup commands to the module. When I initially started playing with these modules,  I used the AT+DMOCONNECT command to initialize the module.  This caused the settings to be reset to which  I thought that the settings were not being saved.  Once the module is programmed, power can be removed and the settings will be remembered.

I have a simple Python program that sends down the programming commands and then you can enter additional commands. I am working on improving it as it’s very basic. Let me know if you are interested in this program. It does require a FDDI USB/Serial usb device. I am using this one:

https://www.sparkfun.com/products/9873

Here are other vendors out there, such as Adafruit (http://www.adafruit.com/product/954), that have similar items.

Other Available Modules and Voltage Ratings

There is another vendor for these types of modules, nicerf.com and their module is sa818. This module has the same programming commands but the voltage indicated seem to show that it can go up to 5.5V. the DRA818 has some conflicting information about the max voltage:

DRA818 Power Specs:

ABSOLUTE MAXIMUM RATINGS 
Symbol Parameter            Min.    Max. Units 
VCC Supply Voltage         -3.3     5      V   
VIN Input voltage          -0.3    VCC+0.3 V 
IIN Input current           -10     10     mA 
TST Storage temperature     -40     90     °C

ELECTRICAL SPECIFICATIONS 
Symbol Parameter (condition)   Min.   Typ.   Max. Units 
VCC Supply Voltage             3.3    4.0    4.5    V 
Freq Frequency range           400           470    <abbr title="Megahertz">MHz</abbr> 
Temp Operating temp range       -20    25     70     °C 
IDD_R Current in receive mode @ Audio amplifier on 60 mA

SA818: wide range of working voltage 3.3 to 5.5 V
Specification: 
Parameter Test condition     Min     Typ    Max    Unit 
Power supply                 3.3     4.2    5.5     V

I have been keeping the voltage around 3.3V and I haven’t pushed it; I may try it 😉