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Working of MSP430FG4618 with Max232 IC ???

Sunil Shelar
Prodigy 20 points
Other Parts Discussed in Thread: MAX232, MSP430FG4618, MAX3232

Hello!!!

I am doing a project using MSP430FG4618 IC and Interfaced MAX232 IC with it but it does not work following are my query 

1. Can i Interface the MAX232/SP232/Max3232 for MSP430FG4618 ???

2. Any substitute IC which can be used to interface with MSP430 FG4618?? 

3. Is any possibility that Reset circuit of MSP430FG4618 is creating problem because some time data transmission occurs when i press reset

Please reply

Thanks in advance

  • 0
    TI__Guru 64510 points

    Firstly, you should be able to use the MSP430FG4618 with an RS-232 transceiver device.  However, you need to make sure you align on the I/O voltage levels as they need to be compatible.

    A quick inspection of the MAX232 indicates this is a 5V device.  You should not connect this up to the MSP430FG4618 which is a 3.3V device (or below).

    I would suggest using the MAX3232 as it supports both 3.3V and 5V I/O signaling levels.

  • 0 in reply to BrandonAzbell
    Guru 227245 points

    BrandonAzbell said:
    A quick inspection of the MAX232 indicates this is a 5V device.  You should not connect this up to the MSP430FG4618 which is a 3.3V device (or below).

    We have used an ST232 (a MAX232 clone) on an MSP. However, this includes some additional parts.
    The output from the MSPS (with VCC of 3.3 or 3.6V) is good for the TX direction. On the RX we had a pullup to VCC and a diode to the ST232, to cut-off the 'high' level of the RX data, letting the ST232 only pull the line low. I don't actually know why we didn't use the MAX3232 at all. This was already there when I started my job. Maybe a cost issue or because these parts have already been in storage. The previous series was built on PICs with 5V supply.
    However, for future designs, I have already planned introducing the MAX3232.

  • 0 in reply to Jens-Michael Gross
    Prodigy 20 points

    dear All,

    I interfaced ready made Max232 IC module interface externally with the MSP430FG4618 it work without any problem but when i built it in the PCB it creates the problem in transmission and reception so any idea what to do

  • 0 in reply to Sunil Shelar
    Expert 1550 points

    How did you connect your MAX232?

    Remember that wrong connections can cause 5V on MSP430 pin.

  • 0 in reply to Sunil Shelar
    Guru 35565 points

    Sunil Shelar said:
    ready made Max232 IC module interface externally with the MSP430FG4618 it work without any problem but when i built it in the PCB it creates the problem in transmission and reception

    Two possibilities:

    1. Your connection to the ready-made module was wrong, but you just happened to get away with it:
      your luck ran out when you put it on your own PCB;
    2. Your connection to the ready-made module was OK, but your own PCB is wrong.

    Without full details of the module, exactly how you connected it, and your PCB design, it is impossible to say more!

    You need to post schematics!

    Others have already noted that the MAX232 is a 5V part, but the MSP430FG4618 isn't - this must be a prime suspect...

    For connection to a PC, rather than mess about with RS232 transceivers, why not just use one of these:

    http://www.ftdichip.com/Products/Cables/USBTTLSerial.htm

    It gives a direct, 3V3 logic-level connection to the micrcontroller's UART - no transceivers necessary!

     

  • 0 in reply to Sunil Shelar
    Guru 227245 points

    Sunil Shelar said:
    when i built it in the PCB it creates the problem in transmission and reception so any idea what to do

    What is the supply voltage.

    Teh ST232 we use works reliable down to 3.6V VCC. So if we power both, MSP and ST232 with 3.6V, things work fine without need for any additional protection circuitry. But going down to 3.3V, transfer becomes flakey and ceases below 3.2V.

  • 0 in reply to Jens-Michael Gross
    Guru 35565 points

    ST232C Product Page: http://www.st.com/internet/analog/product/66106.jsp

    Datasheet: http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00001703.pdf

    Jens-Michael Gross said:
    Teh ST232 we use works reliable down to 3.6V VCC

    The ST232C is specified for operation at 5V +/- 10%

    Operating any device outside its manufacturer's spifications is asking for trouble - the performance is, literally, undefined.

    The fact that you got lucky with the particular devices that you tried, in your particular application, is no guarantee that anyone else will also be so lucky.

    (of course, it doesn't mean that they won't also get lucky - just that there's no guarantee)

    For guaranteed behaviour, always design to the Datasheet - not to anecdotes!

     

  • 0 in reply to Andy Neil
    Guru 227245 points

    Andy Neil said:
    The ST232C is specified for operation at 5V +/- 10%

    Yes, I know. I was pure coincidence that the small converter PCB I had with this device did work on the 5438 breakout board when I set the supply voltage to 3.6V.
    On all our regular designs, we use this one with 5V supply and proper circuitry. The next PCB will have a MAX3232 instead.

    My intention wasn't to recommend this but to tell that the 5V parts may or may not work on such a low voltage and a vew 100mV can make a difference between working out-of-specs and not working out-of-specs,

  • 0 in reply to Jens-Michael Gross
    Guru 35565 points

    Jens-Michael Gross said:

    My intention wasn't to recommend this but to tell that the 5V parts may or may not work on such a low voltage and a vew 100mV can make a difference between working out-of-specs and not working out-of-specs,

    Quite so.

    Unfortunately, I fear that such subtleties are all-too-often lost on the average forum poster.

    :-(

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