MSPM0L1106: Question on GPIO settings :

On the Launchpad there is a resistor connected to PA2 for Rosc. I don't know why they don't put a jumper:

Hi Alan,
Can you share your sysconfig file? I want to check if there may be something wrong with it. Also, the way to set up the output will be to add the "DL_GPIO_enableOutput" function after the initDigitalOutput & setPins. Also keep in mind Keith's comment on the pin having a pull-down resistor in the launchpad.

Best Regards,

Diego Abad

Hi Diego Abad,

I noticed that there is a R6 pull-down resistor in the launchpad and it has the same value in my product. The following is the connection of my testing with lauchpad.

I created empty project and configured PA2 as input without any internal pull resistor. I attached the whole project to you for your reference.empty_new.zip

In my testing, when the switch is closed, PA2 should have ~1.5V. But my measurement is 0V.

Inside the main() function, I added the codes that I set PA2 and PA3 to input and output. (Remark: they are disabled by default by #if and #endif.) I am locking forward on your analysis result. Thank you for your support.

AlanC.

Hi Alan,
It seems to me that the problem relies on the fact that if the pin is not experiencing any voltage input when connected to the pull-down resistor, likely, the resistor's value is impeding doing a reading in the pin, AKA the pull-down value should be reduced. As for your other questions:
2. PA2 seems to have a little voltage when initialized as an input with the pull-up resistor (around 100mv). This is most likely due to the pull-down resistor connected to it (also, it's hard to prove a value out of the small R6 resistor.) However, I do see regular I/O behavior from this pin when configured to output high (3.3V.) Remember that by default, the input reading values should be high impedance, AKA it doesn't really output a signal. For more information, I recommend looking over Figure 9-1. Superset IO Slice in the TRM.
3. I did both tests (input + pull-up & output high,) and both give me around 3.3V. The configuration was done in SYSCONFIG, and the code runs an empty loop.
4. You probably use this function when switching back from another mode, aka output mode. The default functionality for I/Os is input, so the only thing SYSCONFIG has to do is set up its configuration.
Best Regards,
Diego Abad

Hi Diego Abad,

"3. I did both tests (input + pull-up & output high,) and both give me around 3.3V. The configuration was done in SYSCONFIG, and the code runs an empty loop."
With the launchpad itself, I got the same result as you. However my question is when I am set PA2 as input without any pull resistor in SYSCONFIG and added 220K 5V potential divider to it. The voltage on that pin will become 0. The theoretically voltage should be ~1.5xV. Is it caused by the clamping diode on the GPIO? (I'm sorry to tell you that I'm a software guy and not much familiar with the electronic.)

"4. You probably use this function when switching back from another mode, aka output mode. The default functionality for I/Os is input, so the only thing SYSCONFIG has to do is set up its configuration."
No. I am not switching the IO from other mode, just switch between input and output. In my project provided above, PA2 and PA3 are set to input without pull resistor in SYSCONFIG. Before the main loop, if the code that switching PA2 and PA3 to output high by removing the #if and #endif. I found that I cannot measure 3.3V on the pins. If PA2 and PA3 are set to output high in SYSCONFIG directly, it is able to do so. Is there anything wrong in that code?

AlanC.

Hi Alan,
3. Let me consult about this

4.  The configuration you are doing seems good to me (except for the resetGPIO.) However, the if else define statement is weird to me since it seems it runs all codes at the same time (makes it input, then output low, and then output high.) I will try just configuring one at a time, and see what addition of your code makes it break. Something like this:

Hi Diego Abad,

As my understanding, the code above within "#if 0" will not be executed. The others will not be executed.

It just like that value 0 in unsigned char variables will be considered as False and other values are True.

AlanC.

Hi Alan,
I thought the intention was to make the GPIOs change between one functionality and the other. If that's the case, then the I/Os should be configured on whatever SYSCONFIG had configured. Based on the code you sent, this will be PA2 & PA3 as inputs. I think that if you are trying to make them an output and being high, the code bellow should do the trick:

Hi Diego Abad,

Thank you very much on your support. Yes, you are correct. I really want to switch GPIO between input and output in run time.

For the voltage divider question, I am looking forward on your test result.

FYI, there is exactly the same voltage divider on PA17 in our product. The configuration of PA2 and PA17 are same in SYSCFG. But the voltage measured on PA17 is correct. Both our hardware team and I cannot explain it.

AlanC.

Hi Alan,
Sounds good. The code I provided before should make the pins become output. I'll need more time to test this out. I should have an update on this by tomorrow or Monday next week.

Best Regards,

Diego Abad

Hi Alan,
I replicated the setup and noticed a similar behavior to what you mentioned. When R1 is 220K, I get a value of around 22.588mV, while when using 22K, I get a value of 1.158V. The MCU could be draining some of the power at PA2. This could be because of how PA2/ROSC is connected to the FCL circuit of the MCU. My advice for now is to use another pin or a resistor value that gives the voltage you want.
Best Regards,
Diego Abad