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Target microcontroller is not responding

Eric Johansson
Prodigy 120 points

Other Parts Discussed in Thread: MSP430F6721, MSP430F6736

I am trying to establish communication with the MSP430F6721 on our target board using the SPY-BI-WIRE interface and the MSP-FET430UIF programmer and Elprotronic Lite application. The interface between the programmer and target uses the Tag Connect adapter, cable, and clip. The programmer is supplying power to the target, and the RC network on the SBWTDIO line matches the documentation in the TI Hardware Tools User's Guide.

So far we have been unable to establish communication with the target, always getting the "Target microcontroller is not responding!!!" error. We have tried a number of different supply voltages, but no joy. Connecting the FET to a MSP-TS430PZ100B development board with a MSP430F6736 controller works perfectly.

Looking at the SBWTDIO signal, the effect of the RC network is much more pronounced on our target - not a surprise, considering the corresponding cap on the dev board is not loaded (designated DNP). The RC time constant on our target is measured to be 46us - is this possibly the source of the communication issue?

  • 0
    Guru 25210 points

    Eric Johansson said:
    We have tried a number of different supply voltages

    You don't explicitly say, but should we assume that you put a voltmeter probe on the target and verified that the VCC and ground connections from the FET are good?

    Eric Johansson said:
    is this possibly the source of the communication issue

    Easiest way to find out is to turn on the soldering iron and remove the capacitor, no?

    Eric Johansson said:
    The RC time constant on our target is measured to be 46us

    That seems like an awfully long time.

  • 0 in reply to Brian Boorman
    Prodigy 120 points

    Yes, we did verify power and ground connections, both in terms of voltage as well as continuity.

    The small size of the cap makes it hard to replace with the tools I have (getting it off is easy - back on is much more difficult), so I figured I'd ask first before doing this, since we are within the specified value range for the cap.

    Time constant does seem long, but we're actually at half the time constant for the recommended values (47K * 2.2nF = 103 us).

  • 0 in reply to Eric Johansson
    Guru 25210 points

    Looking at the documentation, that does seem correct, and I looked at the one board I've used SBW on and that has 50K/2.2nF combination. I don't think that part is your issue.

    Also, you have nothing else on the SBWTCK other than the MSP and the pod, correct?

    Is there something already programmed into the device that could be locking you out?

    Have you checked the signal integrity of the traces?

  • 0 in reply to Brian Boorman
    Prodigy 120 points

    There is nothing on SBWTCK - just a trace from the pod connector to the MSP pin. Another site suggested that sometimes a 4.7K pull-down resistor on this line can help with communications issues. I tried this, but no difference.

    We have a total of 5 target boards with three different people; we are all running ostensibly the same tools. One person has not had an issue programming any of the boards, but the other person and I are experiencing this same communication issue. The problem seems to be following the MSP-FET430UIFs, not the target boards, so my guess is something about the timing or signal integrity is right on the edge of working/not working. Unfortunately, I don't have easy access to the other FETs to do a side-by-side comparison of the signal characteristics, but we have verified the signals are present on the boards that aren't communicating.

  • 0 in reply to Eric Johansson
    Prodigy 120 points

    Problem was resolved by removing the 2.2nF cap on SBWTDIO and adding the missing 330 ohm resistor between TCK and TEST/Vpp on Tag Connect adapter board.

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