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MSP-FET: Error connecting to the target: Unknown device only on the first attempt

moshe jacobson18
Expert 2210 points
Part Number: MSP-FET
Other Parts Discussed in Thread: MSP430F6736A, , MSP-GANG, MSP430-FLASHER

Hi

I have a MSP-FET sitting betweena win10 PC and my custom board with a MSP430F6736A.
Connection is with a custom 8 wire ribbon cable, length 180mm.
The board is self powered.

An issue that has been annoying me for a long while is this:

The very fist time after reconnecting the FET to the PC & to the board, the FET loads my program without any problem.
The SECOND and SUBSEQUENT times i use the FET to load my program i get "Error connecting to the target:  Unknown device".
Once that message appears, I then click on "Retry" and it loads normally!!

IF, however, i disconnect the FET from the PC (but keep the FET still connected to my powered board) PRIOR to loading my program, the FET loads my program EVERYTIME!

My questions are:
1. How can i get the FET to load my program everytime without having to disconnect it from the PC?
2. Why does this happen?

thanks in advance

  • 0
    TI__Genius 15370 points

    Hi Moshe,

    This sounds like it could be a problem with the hardware connection between the MSP-FET and the MSP430. Are you using SBW or JTAG communication to program the target? Also can you verify that your connections to the MSP430F6736A match the either Figure 2-1 or Figure 2-3 of the MSP430 Hardware Tools User's Guide depending on whether you are using JTAG or SBW respectively.

    Best regards,

    Caleb Overbay

  • 0 in reply to Caleb Overbay
    Expert 2210 points

    Hi Caleb

    I'm using JTAG comms...and yes the connections are as per hardware tools user guide fig 2-1.

  • 0 in reply to Caleb Overbay
    TI__Mastermind 49692 points

    Hi Caleb,

    For your awareness, I've linked to another recent thread that seems to be related.

    Regards,

    James

    MSP Customer Applications

  • 0 in reply to moshe jacobson18
    TI__Genius 15370 points
    Hi Moshe,

    After looking into your MSP-GANG post that James has linked to, can you verify the capacitor value you have on the RST pin? Also make sure you are using an external pull-up resistor on this line as well.

    Best regards,
    Caleb Overbay
  • 0 in reply to Caleb Overbay
    Expert 2210 points
    Hi Caleb

    After i changed the cap to 2.2nF (the external resistor was always on the RST/NMI track) the problem was still 'sort of' there. But it did indicate the cap was part of the problem.

    I then cut my Vcc wire and put a 200ohm resistor...that appeared to download EVERY time.
    However, after a few further sequences of either having that resistor or removing it, i found that there were instances that the problem manifested itself again. Perhaps having it there was better than NOT having it there.

    I then REMOVED the connection Vcc target (Vcc programmer remained disconnected) and i found that the FET downloaded EVERY time.
    So, it would appear that the Vcc target connection is actually superfluous when the board has its own power?!!?

    Unfortunately the above solution didnt help me with the GANG...so maybe the problem with my GANG is its circuitry involving the Vcc target level.

    cheers
    moshe
  • 0 in reply to moshe jacobson18
    TI__Guru* 77971 points
    Hi moshe,

    While it may appear to be working, it is not recommended to remove the target Vcc connection if you are using external power. Basically the MSP-FET (if you use CCS, IAR, MSP430-Flasher, etc) detects whether target Vcc is connected or not and uses that to determine if you are externally or internally powering the target - this is different than the MSP-GANG where you explicitly give it a setting to tell it whether you want to internally or externally power the target.

    If you disconnect target Vcc (JTAG pin 4) but still externally power the target as you are in your test, this is bad practice because the MSP-FET will assume you want the MSP-FET to provide power to the target. While you don't have pin 2 connected on the JTAG header so MSP-FET can't truly provide power, it will potentially output the wrong voltage on the device's JTAG pins and potentially take your part outside of the datasheet spec. E.g. if you powered your board with 3.6V but the MSP-FET was set to supply the default voltage of 3.3V, and you don't have pin 4 target Vcc connected, the MSP-FET will think that all of the signals it is outputting on the JTAG or SBW lines should be at 3.3V, even though your device is at 3.6V - this causes voltage conflicts and can result in strange behavior. It is not recommended. However, if you do correctly connect pin 4 target Vcc when you externally power your board, the MSP-FET will detect the voltage that you are powering your board at, and it will adjust all of its signals on the JTAG/SBW lines accordingly to match that voltage and prevent conflicts.

    Regards,
    Katie
  • 0 in reply to Katie Pier
    Expert 2210 points

    Hi Katie

    I accept what you say....but...what can i do to prevent the FET telling me "unknown device", yet after pressing retry it loads without an issue (till the next time)?

    Perhaps one needs to start with the question - under what circumstances will the the FET display the message "unknown device"....?

    cheers

    moshe

  • 0 in reply to moshe jacobson18
    Expert 2210 points
    Hi Katie & Caleb & others

    I found the issue here.
    Buried in my setup code was "PJDIR = BIT0|BIT1|BIT3;"
    I commented that line out and the problem disappeared!
    (and yes the GANG was similarly affected albeit the message was different)

    thank you for trying.
    Moshe
  • 0 in reply to moshe jacobson18
    TI__Guru* 77971 points
    Wonderful news! Thanks so much for the update and I'm glad that you have resolved your issue. Hopefully by having this posted here it can also help anyone else that might run into the same thing, so thanks for using the E2E forum.

    Best Regards,
    Katie

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