Help connecting RN 171 module

Discussion in 'General Electronics Chat' started by UTLtech, Sep 7, 2011.

  1. UTLtech

    Thread Starter New Member

    Sep 7, 2011
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    Good evening forum.

    First off I just came across this fantastic tool, that shows you how many threads there are that are similar to what I just typed as the title for this thread. very handy ( I am going to drop punctuation for now, sorry )

    My problem arises from the RN 171 WiFly module made by Roving Networks.

    I am new to the field of electronics. So please bear with me. i ASSURE you that I am a fast learner. I will not be taking much of your precious time.

    I recently acquired 4 RN 171 modules from Roving Networks. But I am at a total loss at how to use it. What I mean is the pins.

    Is it a surface mount device? Must the device be mounted on a PCB or can I somehow (after some alteration obviously) mount it on a breadboard/ general board.

    My main aim is to send binary data from a laptop to this chip. The received data sequence will be checked by a strobe for sequence only.

    Please let me know how in the world do I get to use this.
    Please do not tell me to buy another chip as it will make me feel like a fool for spending so much on these modules ( as I know I am a fool :p )

    If you desire any further data from me, please feel free to ask.

    Humbly,
    Vikram
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Welcome to the Forums.

    The datasheet for the RN-171 is available here:
    http://www.rovingnetworks.com/documents/rn-171-ds.pdf

    Yes, it is.
    Yes. The recommended layout is in the datasheet on page 7; antenna requirements on page 8. However, I question the spec for the RF shield; it's indicated as 130 mils thick; 1 Oz copper is 1.4 mils, so their spec is ~93x as thick. I'm thinking that is a typographical error? You should contact the manufacturer about it.
    The RF portion has to be mounted on a PCB, otherwise it won't function properly, and may damage the unit. However, you could connect the data I/O pins to wire pads or pins to enable you to plug the RF pcb into a breadboard, etc.

    You're going to need to define your method of data transfer from the laptop to the IC. USB might be your best approach, as RS-232 is legacy, and won't be included on new systems. You will need to have some way to interface the USB port to your IC.

    Before you try to use these modules (which you say are expensive), you should acquire some other inexpensive ICs that have a similar pin spacing, and practice soldering them to PCBs that you make. Otherwise, you will likely ruin the expensive modules simply because you don't have the requisite experience. Soldering is not intuitive, and no one starts off making perfect solder joints. It takes time, patience, and practice with good equipment. Your first efforts will not be pleasing, but if you are patient enough, your results will improve.

    [eta]
    Before you attempt to solder SMD ICs, you should acquire some cheap resistors and cheap prototype PCBs that are pre-drilled with copper pads, and practice soldering those on. You really need to take this one step at a time, or you will have disappointing results.

    You will need to create schematics, and from the schematic drawings, PCBs, and then either make the PCBs yourself or have them made by a board house. Making a good PCB at home is something of an art in itself. You will need a 2-sided board.

    You should get familiar with a schematic capture and PCB creation software package. I've been using Cadsofts' Eagle for several years. It's not easy to learn at first, but it has many powerful features that are lacking in other packages; and it's available with a "freeware" mode for hobbyists, capable of making up to a 2-sided ~3"x~4" board.

    Sparkfun.com has a tutorial on Eagle, here: http://www.sparkfun.com/tutorials/108
    If you don't have the patience to go completely through the tutorial, there is no point in continuing with the project.
     
    Last edited: Sep 7, 2011
  3. UTLtech

    Thread Starter New Member

    Sep 7, 2011
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    0
    thank you for the prompt and in-depth response.

    i have two questions originating from your detailed response.

    firstly, i do not need a perfect board to test this project. it will be sitting right next to my transmission point. so i think i will try it out on the breadboard before I go for a PCB solution. any advice to a man thats gonna try something stupid? ( which is solder the wires to the module, mount it on the breadboard and power it )

    secondly, i read that the module could be programmed wirelessly. power it, look for the network it creates ( or there is an address thats given to which you can connect ) and do the needful. the only thing that i need changed in the module is the address it reads data from.

    Thirdly ( I just realised i left this bit out )
    this module is not to be used in conjunction with a computer (laptop/desktop). I will just code it, power it with external source, connect it to a basic 4 bit universal shift register and see what is transmitted. ( obviously a microcontroller and all are required, I am leaving those details out )

    Again, SgtWookie ( hey now, star wars fan!)
    Thank you for your help,
    Looking forward to your reply and guidance.

    Vikram
     
  4. UTLtech

    Thread Starter New Member

    Sep 7, 2011
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    0
    wait, you are right. I will need logic level shifter from TTL to rs232 or the USb standards. ugh. okay, so that will be done. kindly respond to the rest.

    Thanks
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    I am on my way out the door, so the rest will have to wait.

    However, haste makes waste. If you just hurry up and slap it together, you will wind up with a pile of broken parts.

    Transmitters need to have carefully tuned antennas or loads attached, or the transmitter will be damaged/destroyed by reflected energy. No time to explain this.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    OK, back for a bit...
    As I mentioned/implied before, the transmitter would likely be damaged if you attempted that. On reading a bit more in the datasheet on page 7, you really need a 4-layer board to create a PCB antenna with the proper impedance, without making the trace for the antenna drastically wide. This precludes the use of the freeware version of Cadsoft Eagle, as it will only support 2-layer boards. It ALSO precludes the use of home-made PCBs, as it would be very difficult for you to try to make one yourself. As an alternative, a PI filter could be used as an impedance matching network to a less elegant antenna; you will have to go that route if using Eagle.

    As far as generating the schematic and PCB, you might consider the use of TinyCad, which is an open-source schematic capture and PCB tool. You could also look into using DipTrace; while a commercial product, it might be sufficient for a project like this. Any way you go, it won't be easy to get the first layout correct. You have a very steep learning curve ahead of you.

    You will also need to implement a boost converter on the board as documented on page 9. That cannot be breadboarded either, as the parasitic capacitances/inductances of breadboaring would simply prevent the boost circuit from working properly.

    If you are a newcomer to electronics, you really need to take on some less difficult projects to begin with, as unless you have someone right there to see what you're doing, your project has a low probably of success.

    I don't know what you mean by "do the needful". I haven't read that part of the datasheet or flyer about the programming. I simply don't have the time and energy to do a lot of in-depth analysis of your project.

    I have no idea about the programming of it. You might be able to use the GPIO for parallel output, or one of the two serial I/O ports for serial I/O.

    [/QUOTE]Again, SgtWookie ( hey now, star wars fan!)
    Thank you for your help[/QUOTE]
    I was assigned the nickname "Wookie" by my commanding officer immediately after our fighter squadron returned from the premier airing of Episode IV, "A New Hope". ;)
     
  7. UTLtech

    Thread Starter New Member

    Sep 7, 2011
    4
    0
    i went through the documentation you provided. very helpful. I also went through the documentation( datasheet ) of the RN-171. It is possible to program the module wirelessly by pulling the GPIO 9 pin to HIGH logic. That is what I will be trying. I just need to feed in an IP to the module to connect to, open a port seeker, transmit a few bits and im done.



    when it comes to the antenna, I hear you. I thought this module comes with an onboard antenna. HOWEVER, this module supports different types. Namely

    Chip antenna, 4” Dipole, PCB trace and wire antenna.

    Im quite new to this antenna business. As stupid as I am, I thought that a dangling wire of sorts connected to the correct pin would suffice. I have already got a bunch of these WiFly modules. i will follow the schematics given on the datasheet. lets see how many modules I have to burn before I realize that its not meant to be that way
    :p

    as of now i am making a regulated power supply to power the sucker up. once thats done. i will start making a small circuit that will act like the antenna. power on. sniff sniff. no silicon burning? proceed to make adhoc network. success

    if only life were that easy.

    Im a huge fan of Star Wars. Perhaps not a hardcore fan. Im a big fan nonetheless. I'm sure you have seen the Robot Chicken parody of Star Wars. Like I said, I love Star Wars, BUT they do a good job.


    Thanks for your prompt replies.
    If there is anything you wish to add and increase my knowledge, please do post here.

    as of now im just worried about the regulated power supply and the antenna. the rest i will manage

    Regards,
    V
     
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