MSP430G2553 static build up causing VLO lockups

Morgan Lowery said:

aside from putting a stronger ground on to dissipate the static

Hopefully by saying "weak ground" you mean weak shield?

You definitely need good layout with separate hi-voltage and logic regions, ground plane on the PCB bottom of whole logic part. You shall minimize possibility for any pin to become antenna that receive EMI or static - configure every unused pin as output (including XIN and XOUT pins), try "toggle LED test" then.

With 'VLO' you mean the MSPs internal very low power oscillator?
I don't see why the VLO should be sensitive to static. I can imagine that the static affects the CPU function, so even though the VLO works, the CPU won't.
The VLO is indeed sensitive to supply voltage changes. Its frequency may largely change over allowed supply voltage range.

Is your watchdog active? Maybe the MST crashes due to static, and is reset by the WDT (causing your test LED flicker introduced by reset and not by varying VLO speed)

Let me give an over view of the product.

This is a dispenser that attaches to a wall. It is powered by 4 D-cell batteries. When the unit dispenses product static electricity is generated and builds up on the unit. To prevent electrostatic discharge we have a wire that attaches from the dispenser roller to a clip that makes contact with the wall. This is the "weak ground" that bleeds off the static. I guess I should have said weak earth ground. 

I set both pins to outputs and get the same issue.

I am using the watchdog timer in interval mode to wake up from sleep.

I added some start up code(delay) and it appears the processor is actually getting reset.

It's usually not a good idea to use the WDT as interval timer (or to disable it) when the device shall run reliably in a noisy enoronment or is exposed to static charge and discharge.

The main purpose of the WDT is to reset the device (hardware reset) if the CPU becomes unresponsible by an ESD event. (even though many peoplpe think the WDT is sort of a firefighter-device for software bugs)

Aparently tis kind of stress is applied to your device and while it often leads to a reset, the MSP sometimes does not recover at all. Because you disabled the funcitonality that was intended to bring it back to life in these situations.

The WTD is an interval timer because the other two timers are uses by the cap sensing.

This is an existing product upgrade from a Microchip product that doesn't seem to be nearly susceptible to the static build up.

Morgan Lowery said:

upgrade from a Microchip product that doesn't seem to be nearly susceptible to the static build up

The PICs I worked with were indeed a bit less fragile. But this is no wonder as they are neither low-voltage (5V supply) nor low-power and also by far not as capable (CPU as well as peripherals) as the MSPs.

Hi Morgan,

i know i´m late but better late than never. I´ve been working with the MSP430G2553 last days using the VLO as source for the ACLK system. The ACLK was used as a source for the TIMER_A0 and all together used as period interrupt generator to recover from the LPM3.

As an indicator for the period of the interrupt generated i used the red led on the Launchpad (P1.0).

When i was debbugging with the Launchpad connected to the PC it worked well. But as soon as i runned the Launchpad from batteries the red led seemed to went mad, and started to blink erratically.

I could see that the strange blinks that was making the red led had a relation with the proximity off my hand, and started to suspect about inducted noise (50Hz, pulsed-mosfet power sources...).

After several hours of unsuccesful tests and cofigurations I decided to look more carefully on the Clock distribution schemes of the MSP430 series.

Finally i reached this conclusion:

I was not setting the correct configuration of BSCTL3.

All my problems went away when i added this two lines of code:

BCSCTL3 |= LFXT1S_2;

P2SEL &= ~BIT6 + ~BIT7; 

It seemed that in a strange way, even if you dont select it, the VLO can act as source for the ACLK when you are debbugging, but when you feed the circuit from batteries the XIN and XOUT pins received all the ambient noise giving the ACLK strange pulses. THis is because the default config for the LFXT1 is a 32768Hz clock.

I hope i have helped! Sorry for being so late!