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MSP-FET: Com port is dropping characters

a b
Prodigy 190 points
Part Number: MSP-FET
Other Parts Discussed in Thread: MSP430FR59941

I am having a problem with the serial port on the MSP-FET.  I'm trying to figure out why it is dropping characters. 

The com port is wired directly to an MSP430FR59941.  These lines are connect to pin 12 &14 on the FET.  (No flow control)

What is being sent (input to the FET): 

Another view (digital & analog):   Note the signal swings from 1.9v-0.11v  The MSP is running off a 1.9v supply.

What Putty is showing:   Last reset b RSTIFG     (Note the "y" is missing)

The problem is more pronounced with the Escape char (0x1B).  i.e. This char gets dropped a lot.

  • 0
    Prodigy 190 points

    I have tried different Putty settings and different terminal emulation modes with no change in the displayed output.  I am not able to sniff the traffic coming out of the MSP-FET, but I suspect the drop is happening in the MSP-FET.  Are there any settings for the MSP-FET?  (I don't know of any.)

  • +1 in reply to a b
    TI__Guru 56685 points

    Hello a b,

    What baud rate are you utilizing?  Cross check with section 5.6.2, Table 4 in the MSP Debuggers User Guide for support baud rates with different settings. 

    Also, by default the MSP-FET connects to the target at 3.3V. You may have to set the MSP-FET target supply voltage to the same as your target supply for it to properly connect. 

    Also please keep in mind that the minimum voltage for the MSP430FR59941 startup is defined by the SVS settings. I would recommend designing your system to operate at the max startup voltage number to ensure robustness of your design across units. 

  • 0 in reply to Jace H
    Prodigy 190 points

    Thank you, this is what I was looking for.

    I was using 115200 baud with no flow control.  (I don't see any flow-control on the MSP430FR59941.)  When I drop down to 19200, I no longer see any dropped chars.  I'd like to use a faster rate.

    I am wondering about section 5.6.2, Table 4.  Why would the MSP-FET care what MCLK the target is using?  (It only see's the resulting baud-rate.)  Is there a setting for the MSP-FET backchannel UART?

    I am not sure what to do with the target VCC setting.  I can't tell if this is a setting for the VCC out of the MSP-FET or if it telling the MSP-FET what the MSP chip VCC value is using.  (I expected the MSP-FET to know what voltage was in use from the JTAG signals.)  Pin 4 of the MSP-FET is connected to my boards 1.9v supply.  Pin 2 is no-connect.  I'm thinking these should be swapped.  If I want to power the MSP-FET from my board, I would supply it to pin 2.  If I wanted to power the MSP chip from the MSP-FET, I would connect pin 4 to my board.  Is this forrect?  (My board is self powered.  I don't want to run the MSP chip off the MSP-FET power.)

  • 0 in reply to a b
    Prodigy 190 points

    Table 5.6.5.2 answers my VCC settings question.  My board appears to be wired correctly.

    The "target VCC" setting is voltage supplied on pin 2 of the MSP-FET.  (Supplied from MSP-FET to the connected hardware.)

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