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Serial Wireless communication

Discussion in 'General Electronics Discussion' started by Nandy, Nov 15, 2013.

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  1. Nandy

    Nandy

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    Nov 15, 2013
    Hello forum,
    I am trying to build a small project to enable serial communication between 2 peripherals. Right now I use an audio stereo cable/jack with 2 pairs and ground. The 2 peripherals are never further away than 50 feet. Right now running the cable is a pain so I want to replace it as long as the project is kept under $50. Much more than that and it would be more cost efficient to just sell the peripherals and buy a new one that will not need the cabling.

    This solution will be applied in the field so it has to be battery powered although one peripheral is powered by a pc usb port so I could use another of the pc usb port for power on that end. The other peripheral end is powered by a 9v battery and I am not sure that battery could take a much higher load and still remain efficient but that can be determined later.

    At this moment all I can use is the commercial software to control the peripherals and its communication so I would like this project to be based on bluetooth technology if possible so later on I can possibly write my own gui and skip the serial to usb peripheral and use my bluetooth in my pc to receive the serial communication.

    I seen the arduino stuff but it is just too pricy. I have consider trying to use an old home wireless phone and adapt it but I am not sure about the power problems and the usage average time is 2 to 4 hours so there are not many wireless phones that can handle that much tx/rc time on battery especially a battery that is as old as the one in this phone.

    Any help will be appreciated. I have a background in electronics and have done many projects and design a few things for myself including game cams back in the day where those will cost you $300+ ( used a old cheap vivitar camera, an ouside motion detector and designed the board with the logic to made them work) . I have etch my own boards, had a little shop for tv/radio repairs back in the 80's when I was a teenager. I just have been away from design for so long I feel I am a dinosaur.... So, help the old man out please!!! lol!

    Thanks!
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    I have done something similar to wirelessly link some devices. I went the arduino and 2.4GHz radio module route.

    Before you complain about price, an ATMEGA328 chip will cost you a couple of dollars and the radio module just over a dollar.

    I was in a hurry when I made my 3 units and used matrix board and wire wrap wire. The transmitters are a bit hungry on power but I accidentally left mine running overnight from a 9v battery using a linear regulator (3v3 is required) and it was still happilly humming away the next day. I can't remember the exact current but i could measure it for you if you're interested.
     
  3. Nandy

    Nandy

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    Nov 15, 2013
    Steve, thanks for your input. I will research a bit on what you mention about the ATMEGA328 chip but I am a bit confused as the arduino stuff I saw was in teh $70 usa and over. Can you elaborate a bit on the components of your project? Tonight I made some progress controlling the peripheral from my android phone using the usb serial dongle with the audio cable and some free software so that is great. Now if I can get the wireless part done I will be in 7th heaven...
    thanks for your help.
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,412
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    Jan 21, 2010
    The things I used were:

    ATMEGA328 and NRF24L01+

    If you Google for them, you'll find lots of information.

    The Arduino site has information about using bare chips.

    Often it makes sense to get a programmer so you don't have to have another arduino to do the programming. The one I have linked to can also provide 5V or 3.3V to the ATMEGA328 which can power your circuit while you're developing it.

    Here is a tutorial that covers most of the bootloader burning issues you'll face.
     
  5. Nandy

    Nandy

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    Nov 15, 2013
    Steve, thanks for the info. will look into it once I make it to my laptop. Before I was looking at http://www.ebay.com/itm/RS232-TTL-L...Master-Slave-Serial-Port-Module-/300914079186. By the description it has seems it might be a "prepackaged" solution. I'm not asking you to do the research just to give me an opinion if you have one. With the light research I did from your response seems your solution is lot more versatile as it gives me the opportunity to program the chip to do most of what I want now and the future.

    Anyway, thanks for your input.
     
    Last edited: Nov 16, 2013
  6. Nandy

    Nandy

    5
    0
    Nov 15, 2013
    well, it seems that module i was looking at earlier does not support 1200 baud rate so it is out...

    update: during more research I found it does support 1200 baud rate.
     
    Last edited: Nov 16, 2013
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,412
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    Jan 21, 2010
    Yeah, those modules look good.

    (Very good... /me motes down to take a closer look at them later.)

    I would certainly go down that route if I didn't need anything more than point to point topology and I had no need for any local processing. And I'm pretty sure your application falls squarely into that category.

    Just beware that you may require some signal processing if the levels required/produced by this module are different from those required/produced by your equipment.

    This last caveat would apply equally to these modules as to any other solution.
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    I too have done some more Googling.

    Firstly, I would advise you to Google for "LC-05 bluetooth" and read some of the issues people have had.

    Whilst I don't think there's anything wrong with these modules, they're certainly not something that will just connect out of the box.

    This thread is from some hackerspace where someone was having trouble making them operate. It was not resolved on the list, I think they did it face to face.

    This site provides some very useful information, including the very useful point: "Be aware default setting of the product is slave mode, communication only avalable between master and slave mode, but not master and master, or slave and slave mode". However it also notes that: "This is a master and slave in one module, switch by using AT commands."

    The latter point as I've noted it here raises the issue of passing AT commands to the units. It may be possible to do this externally, and once set up they will talk to each other at power-up. But this setup might be required each time. If it's the former then as long as you can figure out how to manually do that setup, you're home free. If not, you may need some of that built-in smarts that will require a microcontroller.

    This youtube video is very useful in showing how a basic level translation is done to connect to a 5V device.

    I think you may have some more research to do concentrating on:

    1) how do I make one of the pair a master
    2) Can I save settings and (pairings) so I don't have to initiate them each time the device powers up.
    3) what are the interface requirements for my equipment and how can I convert that to/from the 3V logic of the LC-05
    4) how will I supply 3.3V to the LC-05.
     
  9. Nandy

    Nandy

    5
    0
    Nov 15, 2013
    thanks for your response. Sorry it took me this long to reply back but been tied up big time. finishing up some details and I will revisit this portion of the project. thanks!
     
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