Android to TTL via Bluetooth

Discussion in 'The Projects Forum' started by HarG, Aug 13, 2013.

  1. HarG

    Thread Starter New Member

    Nov 20, 2012
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    Hi Guys,

    Just wondering where to start with this one so looking for suggestions. I am wanting to use an Android app to send some simple commands to a control BUS using bluetooth. The BUS is 5V TTL and the commands are typically just 3 bit commands in Manchester coding.

    I'm ok with the app I think but what would be the best hardware (cheap as well if poss) to use? I've seen quite a few modules that have Tx/Rx serial I/O but as I need to take the control BUS high to low for a '1' I would need something else surely?

    Any help would be very much appreciated.
     
  2. tshuck

    Well-Known Member

    Oct 18, 2012
    3,531
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    Easiest would probably have a microcontroller listening to a bluetooth module and control the bus according to what is sent to it...
     
  3. HarG

    Thread Starter New Member

    Nov 20, 2012
    18
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    Thank you. I am thinking of using an Arduino to begin with.
     
  4. drbenne

    Member

    Jul 30, 2013
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  5. sirch2

    Well-Known Member

    Jan 21, 2013
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    I too have used one of those JY-MCU bluetooth modules with an Arduino and Android phone. They work well but it may be worth noting that the module I had was 3.3v – I used two diodes to drop 5v down to close to that level. Also the JY-MCU module I had was very noisy electrically so screening of the rest of the circuit may be necessary.
     
  6. drbenne

    Member

    Jul 30, 2013
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    hmmm.. The one I received accepts 3.3-6V and I connected it to the 5V pin on the Arduino board and didn't run into any problems. The prebuilt Arduino board also provides a 3.3V pin also if for some reason the 5V is too much.

    If the barebones kit is used, the Atmega328 on the Arduino has a 1.8-5.5V operating range also so i'm sure the voltage can be reduced to power both in that range.
    EDIT: looking at the barebones kit it comes with both a 5V and 3.3V regulator
     
    Last edited: Aug 14, 2013
  7. HarG

    Thread Starter New Member

    Nov 20, 2012
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    Yeah I have seen that board around. Glad everyone else is on the same page!!

    Thanks!
     
  8. sirch2

    Well-Known Member

    Jan 21, 2013
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    But I was running the Ardino at 5V for other reasons and the digital pins were 0-5V. The one I had was definitely 3.3V and I trashed one by running it at 5V. It was only necessary to drop the voltage on the input to the BT module. As you say the Arduino provides 3.3V for power and is happy with a 3.3V Logic high from the BT Module.
     
  9. HarG

    Thread Starter New Member

    Nov 20, 2012
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  10. drbenne

    Member

    Jul 30, 2013
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    I believe this is one of the cheapest sites to get it from also... the BT module that is.. most sites have similar modules running around $50-$60. One thing though is I had to wait a while for it to arrive... close to 3-4 weeks and reading the reviews it looks like some other people had the same issue.

    Also, no datasheet is included but there's enough info out there to get it running.

    Interesting. What version did you have? Looking at mine again, I have v1.05. I believe there is a later version out now
     
  11. drbenne

    Member

    Jul 30, 2013
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    This should work as the JY-MCU I have also only works in slave mode.
    BUT be aware that the one you linked is 3.3V(2.7-4.2V)

    And for limitations of slave modules....

    Taken from another site:
    One end of a BT connection is the master device and the other end is the slave device. The master device generates the clocking signal used for the BT connection and the slave device derives its clock from the received radio signal.

    This results in the following restrictions:
    -A device can be either a slave or a master, but not both. (In the case of this module, slave only)
    -A single master can (optionally) make connections to multiple slaves.
    -A slave can only connect to a single master. It cannot have connections to other masters as it would then need to support multiple clock sources!
    -The BT protocol is asymmetric. At its lowest level, A master can transmit over radio at any time.
    -A slave only transmits in response to a request from a master.
     
    Last edited: Aug 14, 2013
  12. sirch2

    Well-Known Member

    Jan 21, 2013
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    I haven't got it to hand but I think it was somehting 1.02?
     
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