Difference between LaunchPADs - adc and output pin

Rachel Gilbert

Other Parts Discussed in Thread: MSP430G2553

Hi all,

I have been using an old LaunchPAD (pre-December 2011) with an msp430g2553. I was seeing some issues with an output pin (P1.2 – controls a motor circuit) not being set to VCC (3V). This problem was occurring intermittently and each time it did occur the pin was set to 2.4V instead of 3V. See pin A in circuit below (note that there are linear regulators for the sensor and msp that drop the voltage to 3V). I thought that there was something wrong with the LaunchPAD so I changed it out yesterday. Now I’m seeing a similar problem on a different pin (P1.6 – turns on an LED). See pin B in circuit below. The output should be 3V but it’s consistently set to 1.7V. Whenever the LED is triggered to turn on (output at 1.7V), another LED, that’s connected to the power supply, dims. (See table below for a summary)

Another issue is that the value at the ADC pin (P1.1) is different between the different LaunchPADs (pre and post 2011). This makes no sense to me. I have a resistive sensor that the ADC is measuring the voltage of and I tested under identical conditions.

I’ve tested both LaunchPADs with different msp430 chips and there is no difference between chips, only between LaunchPADs.

Pin	Old LaunchPAD	New LaunchPAD
P1.1 (pin C - ADC)	2.6 V	2 V
P1.6 (pin B – LED output)	3 V	1.7 V
P1.2 (pin A – motor output)	2.4 V (intermittently)	3 V

Are there any fundamental differences between pre and post-2011 LaunchPAD? Any ideas on what can cause an output pin to not be set to VCC? Any ideas on what can cause the ADC value to change between LaunchPADs?

Thanks!

over 12 years ago

0 old_cow_yellow over 12 years ago

Guru 58965 points

You need to remove all the jumpers (on both the old and new board).

0 old_cow_yellow over 12 years ago in reply to old_cow_yellow

Guru 58965 points

My previous comment assumes that the code is already downloaded to the chip and it has been debugged already.

If you want to download and debug, you cannot use your own 3V power supply. You need to disconnect that and put the Vcc jumper back. You also need the RST and TEST jumpers. (But remove all others except the above 3 jumpers.)

0 Rachel Gilbert over 12 years ago in reply to old_cow_yellow

Prodigy 210 points

Yes the code has been downloaded and debugged. Why do I need to remove all the jumpers?

0 old_cow_yellow over 12 years ago in reply to Rachel Gilbert

Guru 58965 points

Because P1.1, P1.2, and P1.6 are already connected through jumpers to something else on the board. And they are in conflict with your additional wiring.

Vcc is also connected through a jumper to an on board power source. It will fight with your power supply if that jumper is not removed.

0 Rachel Gilbert over 12 years ago in reply to old_cow_yellow

Prodigy 210 points

Problem fixed! Thank you

0 Rachel Gilbert over 12 years ago in reply to Rachel Gilbert

Prodigy 210 points

Sorry to re-enter this question but does it matter if the jumper's connected even if I'm not using uart?

0 old_cow_yellow over 12 years ago in reply to Rachel Gilbert

Guru 58965 points

Some of the pins of the socket are already connected to some other parts of the board. If any of these connections is in conflict with your intended use of the pins, it would not work for you. You need to break all those conflicting connections. If there is a jumper there, you can do so by removing the jumper.

0 Jens-Michael Gross over 12 years ago in reply to Rachel Gilbert

Guru 227245 points

Rachel Gilbert said:
does it matter if the jumper's connected even if I'm not using uart?

Sure. It is unimportant whether you use the UART. Even if you don't, the pin is still connected to the counterpart when the jumpers are set. So you're still receiving UART signals (you just ignore it).
Not listening to the music does not switch it off - it still makes conversation difficult. :)

0 Rachel Gilbert over 12 years ago in reply to Jens-Michael Gross

Prodigy 210 points

Thanks! Great analogy. I disconnected the jumpers and the previous problems were fixed.

Unfortunately, now I'm seeing a problem of the msp sometimes not responding to the adc input. When the input reaches a certain value, P1.6 should be turned low but this doesn't happen. I checked the voltage at the adc pin (P1.1) and it does reach the correct voltage. Is there anything that could cause the msp to freeze up and not respond to an input?

0 Jens-Michael Gross over 12 years ago in reply to Rachel Gilbert

Guru 227245 points

Rachel Gilbert said:
Is there anything that could cause the msp to freeze up and not respond to an input?

Several. Including your code :) There might be a racing condition or deadlock situation.
Without knowing the code, I can't tell.
It's rather unlikely that a hardware problem is the reason, especially since you checked the voltage (with scope or multimeter? A multimeter only shows an average, so in theory, the real voltage could be low with some high spikes that are missed by the ADC)

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Difference between LaunchPADs - adc and output pin