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MSP430FR5969: Multiple Transmitter and single receiver in UART?

Anil Dhanawade
Expert 2760 points

Part Number: MSP430FR5969

Hello All,

Is it possible to receive the data on the RX(UART) pin of MSP430, by using 2 different TX lines.?

Like I have MSP1,MSP2, MSP3. MSP3 is a RX and MSP1 & MSP2 is the transmitter (UART). SO both MSP1 & 2's TX pons are connected to RX pin of MSP3. Is it possible? 

if YES then how it works and NO then why no?

Thanks 

Anil D.

  • 0
    TI__Mastermind 46765 points
    Hi Anil,
    One question, what if the MSP1 and MSP2 want to send messages to MSP3 at the same time? Who is going to control the bus?

    Best regards,
    Cash Hao
  • 0 in reply to Cash Hao11
    Expert 2760 points
    Hello Cash,

    This is UART so i think there is no control assumption is working here like I2C.
    In UART MSP1 (MSP430FR5969 - 1) and MSP2 (MSP430FR5969 - 2) i just want to know that we can do like this one or not.
    Don't bother about data. MSP1/MSp2 can send any kind of data to MSP3. At the different time stamp.
    you can consider the same time stamp also.

    regards,
    Anil D.
  • 0
    Guru 102845 points

    For UART serial, the transmitter is expected to drive (not pull) the TX line high/low. With multiple transmitters, there will be a bus conflict, and you'll get artifacts like 1.5V levels on the wire.

    It's possible to imagine UART-serial running over an open-drain-ish bus (electrically analogous to I2C), but I haven't seen it done and I'm pretty sure the MSP430 wouldn't know how.

  • 0
    Guru 34973 points

    Anil Dhanawade said:

    Part Number: MSP430FR5969

    Is it possible to receive the data on the RX(UART) pin of MSP430, by using 2 different TX lines.?

    Like I have MSP1,MSP2, MSP3. MSP3 is a RX and MSP1 & MSP2 is the transmitter (UART). SO both MSP1 & 2's TX pons are connected to RX pin of MSP3. Is it possible? 

    if YES then how it works and NO then why no?

    For this I will use mailbox system data exchange during runtime. One master device, and 3 (or more) slaves, without problems. Sending double world at once, not byte by byte. SBW will take 2 (not used for anything else) lines (TEST / RESET) on target devices, without occupying any hardware peripheral on master / slave devices.

    Or I2C, if there are pins on target device free / available, and there is no possibility that communication lock the buss.

  • 0 in reply to zrno soli
    Expert 2760 points
    Hello ZRNO,

    i really not getting anything.
    My simple question is that, Is is possible to connect 2 TX Lines to 1 RX Line (UART). i will send the data alternatively, so that RX is capable to RX the data or not?

    Thnaks
    Anil D.
  • 0 in reply to Bruce McKenney
    Expert 2760 points

    Hi Bruce,

    First Line:

    MSP1 is TX data, then it goes to RX of MSP3 and TX of MSP2. So how the conflict will happen? RX is receiving the data, then how that things are affected to TX pin.

    Can you please give me some more detailed information.

    Second Line: 

    I am not getting what you actually wants to say. Please give me the information about it.

    Thanks 

    Anil D.

  • 0 in reply to Anil Dhanawade
    Guru 102845 points
    From your description (perhaps a diagram would work better) MSP1 and MSP2 are both driving the same wire (TX to MSP3). If MSP1 drives it high, and MSP2 low, there will be a conflict and the actual resultant level will be indeterminate.
  • 0 in reply to Anil Dhanawade
    Guru 34973 points
    My point is that you have 5xx devices that exchange data, and that you can chose what ever you want for communication between devices. There is no "big" issues if there is one UART transmitter, and more than one UART receiver, but for more than one transmitter, there are other options available. One of the reasons why I am not big fan of FR family is that they don't have port mapping option, like 5xx flash devices, where is possible to remap UART hardware module TX / RX lines during runtime on different port pins, and this maybe can help to resolve similar problems like yours.
  • 0 in reply to Bruce McKenney
    Expert 2760 points

    hello Bruce,

    you are talking about the assumption,

    lets take one assumption.

    alternatively data will be send, like MSP1 send at x time and MSP2 is send at another time. then its possible?

    In determinant condition will occur when 2 MSP's (1 & 2) are sending the data at the same time?

    Ok thanks 

    Regards 

    Anil D. 

  • 0 in reply to zrno soli
    Expert 2760 points
    ok, let me check.

    Thanks
  • 0 in reply to Anil Dhanawade
    Guru 102845 points
    I've only assumed what you've told me. The electrical conflict will occur any time either MSP1 or MSP2 sends anything.

    What is it you're trying to accomplish? I2C is a multi-master multidrop bus. Is there a reason not to use that?
  • 0 in reply to Bruce McKenney
    Expert 2760 points
    Yes you are right,

    defently conflict will occur because of voltage levels.

    Thanks
  • 0
    Genius 3255 points
    Have you considered sharing another line aside from RX/TX and GND? You could create a Collision Detection scheme where a transmitter sets the extra line during transmission and begins transmission only if the line is not set by another transmitter. If all inactive transmitters change their TX lines to high Z when idle, you should be able to allow for more than just 2 transmitters.

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