I would like to implement a pulse-sensitive, aka edge-triggered, interrupt on an LPC1759 microcontroller. In the UM10360.pdf datasheet and ARM Cortex-M3 user guide, it says that interrupts can be triggered based on level- or pulse-sensitive behavior, but I am unable to find how to set this to be pulse-sensitive. Can someone please tell me where to set this?
For my particular application(interfacing the LPC1759 with an AD7794 ADC), I would like to trigger an interrupt based on the falling edge of the MISO pin. Although it is not explicitly stated that the interrupt is trigger on the MISO value, I am assuming this based on the fact that, of the four SPI signals, the MISO is the only input to the microcontroller. Please let me know if this is not correct.
See UM10360.pdf, chapter 9.5.6: "GPIO interrupt registers". You can enable rising and falling edge interrupts only on port 0 and 2 pins. The interrupt vector is the same as external interrupt 3.
Related
void EXTI4_15_IRQHandler()
{
if(EXTI->PR & EXTI_PR_PR8)
{
EXTI->PR |= EXTI_PR_PR8;
// handle interrupt here
GPIOA->BSRR |= GPIO_BSRR_BS_10;
Delay(500);
GPIOA->BSRR |= GPIO_BSRR_BR_10;
Delay(500);
}
}
the interrupt init is initialized in the main.c and the setup is correct.
Is there anything that i am missing in the handler function?
You have posted only interrupt handler function, which is not a big help on its own. Basically, your MCU either enters it and executes it entirely or not. So if it (the interrupt handler) doesn't run, it means, the interrupt is not triggered. It means, the problem is somewhere else, so I will go over the entire logic of getting EXTI interrupt on STM32, make sure you have all of that done.
In order to get EXTI interrupts working, we need to connect 3 internal peripherals together: GPIO, EXTI and NVIC. You haven't indicated a specific microcontroller, but they all (STM32) do it in the same/similar way, so I will use STM32F746 as an example, since I have it here on my table.
First, you need to set up EXTI. If you want an interrupt on pin GPIOx8, you need to set bits 8 in the appropriate places in the EXTI registers depending on the event you want to trigger an interrupt.
Second of all, you need to connect GPIO port to EXTI. Do you want an interrupt on PA8? Or PB8? Or PC8? EXTI only understands that it's "Pin 8". It doesn't know if it's PA8 or PB8. That you do in SYSCFG peripheral. In the register EXTI->EXTICR3 you need to set port for EXTI8. This is where you decide that it's PB8 and not PA8 that triggers the interrupt, or whatever port you have.
Now, upon the GPIO behavior event defined in EXTI, the EXTI will report an EXTI9_5 event to NVIC. For now, NVIC will set pending bit if EXTI interrupt event occurs, but it will not execute the interrupt, because it's not activated. So we need to configure NVIC and activate EXTI9_5 interrupt there. At this point your interrupt should work.
To recap, the sequence of actions is the following:
Configure EXTI with the number of pin, on which you want interrupt. Number of pin, but not a GPIO port. For you, it will be pin 8.
Configure SYSCFG to select GPIO port for that EXTI pin. Configure pin 8 to be pin PB8 and not PA8 (or whatever port the interrupt is on).
Activate the corresponding NVIC interrupt.
From this also follows, that you can't have interrupts on PA8 and PB8 at the same time.
EDIT: having delays in the ISR is highly inadvisable. Also, make sure your input signal on the interrupt pin is debounced.
EDIT2: I assumed it goes without saying that every peripheral you use requires clock to be supplied to it.
From what I understand, the interrupts are enabled by using the below approach :
The steps 1) through 9) are followed in a general EXTI programming.
There are two sides for enabling and clearing the interrupt :
Peripheral Side : gets enabled by SYSCFG, EXTI blocks and also cleared in the pending register EXTI_PR once interrupt is encountered.
Processor Side : NVIC->ISER to enable. But in spite of NVIC->ICPR being there I don't see that it's being used to clear the processor side for pending register. Why?
Are there any peripheral side interrupt generators too which also don't have any pending register that required to be cleared?
Any document which explains these also would be greatly appreciated.
It is the same with all other peripheral registers. The clear path is not important from the programmer point of view. The important is information how to clear the bit.
Clear the bit you need to clear bit EXTI PR register.
Clearing sometimes happen indirectly (for example by reading the data register in some communication registers). Some peripherals have special registers only for clearing the pending bit. Example: DMA
Everything is in the Reference Manual.
Clearing the flag in the peripheral register deasserts the interrupt line coming to NVIC form peripheral.
I want to enable the PA8 pin in a processor (Atmel SAM3X / SAM3A). I have set PIOA_MDERp[7]=0 and PIOA_MDDR[7]=0 and PIO_OER[7]=0 and PIO_ODR[7]=1, so that the tri-state buffer will no longer send data out of the pin, and the pin is enabled to receive data from the environment and to send interrupts if needed. I also want to set my interrupt to rising edge, so I also did PIOA_RHLSR[7]=1 and PIOA_FELLSR[7]=0 and also PIO_ESR[7]=1 and PIOA_LSR[7]=0.
My problem now is how to modify NVIC registers so that this interrupt is enabled. I mean, on a rising edge on this pin, the state of this pin is pending, and then the changes I will apply to NVIC causes this pending state to active state.
My interrupt group priority and subgroup priority are both 3.
I know how to modify Interrupt set-enable register, interrupt clear-enable register, application interrupt and reset control register, and interrupt priority register. Still, my problem is that now I don't have any number for interrupts from this specific pin (PIOA8), so it is different from the time I had my interrupt number (from 1 to 240), and so I could know which register in the NVIC I should modify.
Thanks for your help.
I need to create a virtual uart port on a stm32 microcontroller. The pins are given and can be changed to timer input channels. The recieving signal is going to be modulated in current and voltage and i need to detect both. Those two pins can not be assigned to a uart. Does somebody has a tutorial or something, that can lead me in the right direction? I just started programming microcontrollers and i am still strugeling with all the timer, interrupts and details stuff.
If we are talking aobut baudrates for small (9600), then you can achieve this with timer and EXTI.
On EXTI set pin to rising and falling edge and between each IRQs check timer value.
If value is greater than start and stop condition time, you failed, else you have to check time spent for EXTi and calculate whether you received 10101010 or 11001100 or any other combination.
For TX mode, use timer for precise interrupts at bit slice for UART output data and create state machine for data output bit by bit.
Another option is to use SPI as virtual UART.
I've been trying to port some of my AVR code to drive a simple SPI LCD to ARM as a learning exercise (I'm very new to ARM in general). For this I just need to use SPI in master mode.
I looked in the datasheet for my device (STM32F103C8) and found that the SPI1 pins I need, SCK and MOSI are mapped as alternative functions of PA5 and PA7, respectively, along with other peripherals (pg.29). My understanding is that in order to use the SPI function on these pins, I need to make sure that anything else mapped to the same pin is disabled. When looking at the defaults for the peripheral clock control register, however, it looks like the other features are already disabled.
I looked at the SPI section in the reference manual, including section 25.3.3 - Configuring the SPI in master mode. First I enabled the SPI1 master clock in APB2ENR and followed the steps in this section to configure SPI1 to my needs. I also changed the settings for PA5/7 to set their mode to "Alternate Function Output push-pull" (9.1.4). Finally, I enabled SPI1 by setting CR1_SPE.
From my reading, I had thought that by loading a value into the SPI1 data register after configuring SPI as above, the data would be shifted out. However, after writing the data, the TXE flag in the SPI status register never becomes set, indicating that the data I wrote into it is just sat there.
At this point, I'm assuming that there is something else I've failed to configure correctly. For example, I'm not 100% sure about what to do with the PA5/7 pins. I've tried to understand what I can from the datasheets, but I'm not getting anywhere. Is there anything else that needs to be done before it'll work?
I'm almost certain that you did not set SSM and SSI bits in SPIx->CR1 register. SPI in these chips is pretty simple, for the polled transfers you need to set SSM, SSI, SPE, MSTR, correct format (LSBFIRST, CPOL, CPHA) and proper baudrate (BR) in SPIx->CR1 and you're good to go.