Why Would STM32F334 GPIO Port A Pin15 MODER Register Read "0x-2"

[ambrose]

Hi, I had a weird issue with an STM32F334 MCU. A pin was configured as Open Drain - this pin is used for falling edge interrupt and pulled up by a different section of the design. But I had issue today with the operation of the pin and realised the MODER Register read "0x-2". What does this mean please? I have solved this issue by locking the pin, but I just want to know if this makes any sense. I am using Ride 7 IDE.

[TDK]

PA15 is configured with a pullup after reset as it's a JTAG pin.

[ambrose]

Hi, thanks a million for the response. this is true, but my issue occurs after the application has been running for a while. It actually forces the pin low.

[waclawek.jan]

> But I had issue today with the operation of the pin and realised the MODER Register read "0x-2".

Show, together with other pins and perhaps also the correct setting for this pin.

There are probably not many RIDE users here.

If GPIOx_MODER register changes "spuriously" (which almost always means some bug in code), you can try to catch it by setting a data breakpoint (sometimes called watchpoint) onto the given register.

JW

[ambrose]

Thanks for the response. Yes it "almost always means some bug in code", but there is no reference to that pin any where in the code after configuration. But I am not really bothered about this bug; this product has been on sale for over 5 years and customers are happy. … My question should probably be "does "0x-2" that is "zero-ex-dash-two" in a register mean anything? Or is it just the IDE?" (BTW, I am not using Ride 7 for version 2 of this product, but STM32CubeIDE.

[Bob S]

> but there is no reference to that pin any where in the code after configuration

Then you have a stray pointer somewhere. And if it is (trying to) clobber the MODER, what else might be getting overwritten?

> But I am not really bothered about this bug; this product has been on sale for

> over 5 years and customers are happy

What The ?????? Maybe your device works "well enough" but your customers know "you just have to power cycle it once in a while" (kinda like Windows). Or maybe everything else really is OK. But you will never know until you find the source of the problem.

> "does "0x-2" that is "zero-ex-dash-two" in a register mean anything?

My guess (and it is just a guess) is that you have expanded the 32-bit MODER register to show each individual pair of bits??? And the dash just means there aren't really that many bits.

[ambrose]

thanks a million. hahahahahahahahahahahahahaha

>>>> Then you have a stray pointer somewhere. And if it is (trying to) clobber the MODER, what else might be getting overwritten?

I sure hope not (LOL).

>>>>What The ?????? Maybe your device works "well enough" but your customers know "you just have to power cycle it once in a while" (kinda like Windows). Or maybe everything else really is OK. But you will never know until you find the source of the problem.

When this happened a line that affects 9 different boards was pulled low. this means 36 channels will be stuck in one state... This will certainly make our customers scream at us _ I know, and I know them.

It could have been a fluke. who knows?

>>>>My guess (and it is just a guess) is that you have expanded the 32-bit MODER register to show each individual pair of bits??? And the dash just means there aren't really that many bits.

Don't remember doing that.

[TDK]

“0x-2�? is not a 32bit integer value and cannot be in a 32 bit register.

[ambrose]

Off course it is not a number. That is the point of this question.

[TDK]

Maybe you can share a screenshot or something that would explain better. It’s certainly not the value in the register, so it must be a display thing in whatever you’re using to view it.