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MSP430 does not work if FET-UIF is disconnected from computer

Gabriel Attuati
Prodigy 30 points
Other Parts Discussed in Thread: MSP430F47197

Hello, i`m developing a energy meter using MSP430F47197 for a research project here in my university. The meter itself is actually finished, and i have a prototype board working, now i`m just making adjustments.

But i noticed something doing tests here in the protoboard: If i disconnect the MSP-FET430UIF from the USB of my laptop, the MSP on my board just stops working, and if i put it again in the USB, the MSP starts working again.

The connections on the on the JTAG interface are all correct, and this fact only happens in my protoboard, because the MSP on the prototype is working fine.

I think it has to be a problem with the power source, because in the prototype i use a 5v cellphone adapter, and in the protoboard i use a regular workbench source. I also tought it may be a ground thing, but i`m not sure of anything, and i would like to ask advice from you guys.

 

  • 0
    TI__Expert 6140 points

    Gabriel, 

    What do you mean by "not working"? Is the MSP430 resetting? Is it running at all? Do you have LEDs on your board for debugging? Have you check the VCC vs. MCLK requirements on the datasheet? 

    Damian 

  • 0 in reply to Damian Szmulewicz
    Prodigy 30 points

    I have a LED blinking every 1 second, and it stops blinking. The MSP send things to a LCD 16x2, and it stops sending. When i put the JTAG on the USB, everything starts working fine again.

    I run the MSP at 16MHZ in a 3.3V input, so it's everything fine in this point.

  • 0
    Guru 95685 points

    Do you have a pullup on the Reset line? That would be an easy way to generate this symptom. (Not that I've ever done that.)

  • 0 in reply to Bruce McKenney
    Guru 227245 points

    Bruce McKenney47378 said:
    Do you have a pullup on the Reset line? That would be an easy way to generate this symptom. (Not that I've ever done that.)

    A pullup on reset to release it (even though most of the 5x family devices have an internal pullup, excluding the 54xx) and a pulldown capacitor, to give VCC time to rise above BOR before reset is released. This is necessary for supplies with rather slowly rising VCC (several µs to ms for a rise from BOR trigger level to safe operating voltage)

    BOR cannot precisely trigger a reset at the edge of minimum operating voltage. It's comparison voltage has a rather large tolerance. For a precise trigger point, a precise referene would be needed which would draw significant current. So there is a small window between BOR release and safe operating conditions. There is a delay to kepp the MSP in reset for some additional time, but if VCC is rising slowly, this delay isn't enough and the external cap on RST helps keepign the MSP in reset long enough while VCC is still rising.

  • 0 in reply to Jens-Michael Gross
    Prodigy 30 points

    Yeah, i have a pull up resistor and a pull down capacitor on the RST pin. 

    The crazy thing is that today when i arrived here at work, the protoboard was working ok without the JTAG. But after i made some changes in the program and wrote it again in the MSP, it stoped working again without the jtag.

    I don`t know, but i noticed that the TDO/TDI pin receive 3.3 volts from the JTAG, and after you take the JTAG out this voltage disappears, and i think that this may cause some interference on the MSP, and cause a reset or something.

  • 0 in reply to Gabriel Attuati
    TI__Expert 6140 points

    Gabriel, 

    I would send send a special command to the LCD (or blink an LED) at the very beginning in main (after you disable WDT) to figure out whether the problem is causing a reset. If you MSP is resetting, then you will see if with this method. You may be having a problem with voltage/frequency violations or incorrect waking from an LPM mode. 

    Damian 

  • 0
    Mastermind 8615 points

    Gabriel Attuati said:

    But i noticed something doing tests here in the protoboard: If i disconnect the MSP-FET430UIF from the USB of my laptop, the MSP on my board just stops working, and if i put it again in the USB, the MSP starts working again.

    Of course it stops working when you disconnect the FET from where it is loading the code! I didn't get quite well this part!

  • 0 in reply to Gabriel Attuati
    Guru 46710 points

    Gabriel Attuati said:
    I run the MSP at 16MHZ in a 3.3V input, so it's everything fine in this point.

    Gabriel Attuati said:
    The crazy thing is that today when i arrived here at work, the protoboard was working ok without the JTAG. But after i made some changes in the program and wrote it again in the MSP, it stoped working again without the jtag.

    Most probably you have problems with how or when you configure clock for 16MHz. If possible, try to put 100ms delay after power-on, before clock freq change __delay_cycles(100000) and see - does it help your board to operate without JTAG connection. Alternate approach possibly could be just to monitor VCC (using SVS?) and set clock only when VCC reach nominal level.

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