The Propeller And IC RN42-I/RM... Will This Work?

idbruceidbruce Posts: 6,134
edited 2020-08-28 - 15:23:42 in Propeller 1
Hello Everyone

I want to be able to communicate with the Propeller through Bluetooth using the RN42-I/RM, but I am looking for minimal circuitry. I believe this should work with direct connections to (2) Propeller IO pins, with perhaps some resistors inline, but I could be wrong :)

Did I mention that I am not an electronics genius? :)

Pin #4 (GPIO7) sets the baud rate to 9600.

As asked in the title, will this work as shown? The datasheet is attached below.

RN42.png
369 x 270 - 21K

Comments

  • Peter JakackiPeter Jakacki Posts: 9,597
    edited 2020-09-06 - 00:40:24
    I just checked the price for these RN42 modules, yikes! When ESP32 modules from Mouser/Digikey are under $4, a BT only module seems very expensive. However it looks like according to fig1-1 in the datasheet that you only need rx/tx and that's fine but make sure you allow for some bulk decoupling right next to the supply in case your regulator is far away (as in inches). Sometimes it doesn't hurt to give RF modules their own regulator if it is easy enough. The ds shows a TC1185 but there is nothing special about that and there are plenty available in small packages. But I am just saying that in general and the RN42 only draws 50ma max.

    You are forcing GPIO4 high for 9600 baud but why such a slow baud rate when the default is 115200? However, there is no problem allowing for a resistor there since you can then decide to place it or not.

    Allow for those LEDs as they may be useful when you are testing the prototype. If you allow for components you don't have to load them in production but you can load them during prototyping.

    If your pcb will allow for it I would place the SPI header as per the example application circuit which btw is a terrible example. I wish sometimes they would show examples that are at both extremes, so a minimal use case. I notice too that although the module has USB capabilities, that they use an FT232R for serial!!! :) :(

    So go ahead with the minimum but make sure the smd pads extend out enough, maybe more than they recommend since this makes it easier for you to access with the soldering iron. I probably would only solder up those pads you are using and maybe a couple of others, just enough to secure it to the pcb, but not too many so that you can't remove it. At least for the prototype.

    Yes, it will work!

    P.S. If you terminate every connection to a small through-hole pad where you have room, then you can use this for testing or mods. Check what I did in the P2PAL for the ESP32 module.
  • Peter

    Thank you very much for taking the time to answer my question :) I do sincerely appreciate it.
    You are forcing GPIO4 high for 9600 baud but why such a slow baud rate when the default is 115200? However, there is no problem allowing for a resistor there since you can then decide to place it or not.

    I went that route, because the Parallax module has that set as the default baud rate and it worked perfectly for my application, but as you say, I can leave it out. I will probably test without the resistor and see how well it works for my application.
    Allow for those LEDs as they may be useful when you are testing the prototype. If you allow for components you don't have to load them in production but you can load them during prototyping.

    That is very good advice :) However it does take time to draw all the circuitry :) I had forgotten how tedious this stuff was :) I just discovered errors in my current layout from moving stuff back and forth :(

    I just sold some car parts :) I do believe it is time for a beer run :) Then I can make more mistakes :)

    THANK YOU PETER :)
  • If my wife tells me she is missing an ingredient for dinner, I say "no problem, we have wine". If I need to run a Windows app on Linux, I say "no problem, I have Wine". So no matter the problem, wine makes it better :)

    Here's one tiny little tip to designing pcbs: fix the positions of your connectors where they need to be and then place and orient parts so that it is almost lining up as much as possible, especially the critical routing. If necessary revisit any fixed positions and optimize. If your signals are having to via to other layers and back again too often then this is a sign that it could be optimized more.

    When everything is placed optimally then routing is a pleasure although the 90/10 rule still applies, that 90% of the work will take 10% of the time, and 10% of the work will take 90% of the time.

  • idbruceidbruce Posts: 6,134
    edited 2020-09-06 - 02:11:08
    If my wife tells me she is missing an ingredient for dinner, I say "no problem, we have wine". If I need to run a Windows app on Linux, I say "no problem, I have Wine". So no matter the problem, wine makes it better :)

    LOL.... So what you are telling me is that I should buy some wine instead of beer :wink: That is also probably very good advice :)
    When everything is placed optimally then routing is a pleasure although the 90/10 rule still applies, that 90% of the work will take 10% of the time, and 10% of the work will take 90% of the time.

    That holds true for most of the work that I get into, not just PCBs.
  • Beer for spicy foods I say, although my wife doesn't like the smell of beer on my breath :( but she has never complained about wine though :)

    That darned 90/10 rule rules. No way around it.
  • The thought of wine really sounded good and I had to ponder my choice for a moment or two, but I opted for the beer. :) With a beer in hand, and eleven more sitting in the fridge, I am ready to make a plethora of mistakes :) And who cares anyhow....? :) I can fix them all tomorrow :)

    I prefer white wine, but mostly a good Chardonay.
  • Mistakes? I'm on site (again) and I hit a snag so I'm doing what I do when possible and adjourn to the pub down the road. Already figured out the problem (I think) so it's time to go back.
    Only problem is that this place is really hopping....loud music, people dancing around and young women who insist on speaking to me...one more pint and I'm outta here...says he :lol:
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