STM32F303RE: unwanted interrupt

[laurentwawrzyniak9]

Posted on September 14, 2015 at 18:12

I have an EXTI programmed on PortB line8 that works as expected when  a rising edge is found on GPIO_IN8.

Unfortunaltely sometimes, when I reset the GPIO_Pin15 of port B by doing  GPIOB->BRR  = GPIO_Pin_15  then the GPIO_IN8 is also affected generating an unwanted EXTI on line 8.

There are no shortcut between pin15 and pin8.

I noticed this happens when I modify the Trig mode of the timer 1 from SlaveMode_Gated to no slaved mode.

This timer1 is  used to trig ADC1.

I don't understand what's happen.

Any idea / suggestion to help to fix this issue ?

Regards

[waclawek.jan]

Posted on September 15, 2015 at 09:50

>  Unfortunaltely sometimes, when I reset the GPIO_Pin15 of port B by doing  GPIOB->BRR  = GPIO_Pin_15  then the GPIO_IN8 is also affected generating an unwanted EXTI on line 8.

> There are no shortcut between pin15 and pin8.

Even if there's no ''hard'' short, you still may have capacitive coupling between the pins, or they can be coupled through some common ground resistance (which rises the questions of proper power/ground distribution and decoupling). You did not tell us what is connected to these pins. Try decreasing the impedance of PB8 (add pullup/pulldown and/or some capacitance) or decreasing the drive of PB15 (setting in GPIOx_OSPEEDR) thus increasing rise/fall time. Did any of this solve the problem?

> I noticed this happens when I modify the Trig mode of the timer 1 from SlaveMode_Gated to no slaved mode. This timer1 is  used to trig ADC1.

This is a completely bogus information - how is this related to PB8/PB15?

Write a minimal example which exhibits the problem.

JW

[laurentwawrzyniak9]

Posted on September 15, 2015 at 14:40

> Even if there's no ''hard'' short, you still may have capacitive coupling between the pins, or they can be coupled through some common ground resistance (which rises the questions of proper power/ground distribution and decoupling). You did not tell us what is connected to these pins. Try decreasing the impedance of PB8 (add pullup/pulldown and/or some capacitance) or decreasing the drive of PB15 (setting in GPIOx_OSPEEDR) thus increasing rise/fall time. Did any of this solve the problem?

Thank you for suggestion, i will test it ASAP.

> This is a completely bogus information - how is this related to PB8/PB15?

That is a good question because there's no relation ship between TIM1 and PB8/PB15.

But the issue occurs when I change the TIM1  internal  input trig mode !

Regards