I have ATmega32 AVR and I want to have more Interrupt pins than (INT 0, INT 1, INT 2)
so Can I convert any pins in ATmega32 to an interrupt or there is another method to have more interrupts in the micro controller? Or should I get another AVR microcontroller?
INT0/INT1/INT2 and pins assigned to them in Atmega32 have special features, for example to wake up MCU from energy saving modes. If you need another interrupt with special feature but on diffrent pin then it is not possible, but... if you want to check input pin state and then execute some actions there is workaround that I used a few times.
So, how external interrupts works?
(Simplified, pseudo-description) There is a special hardware controller inside your MCU that detect rise-up/down, change of chosen pins and when certain condition is met, it reports to interrupt controller what happened, then if mask bit of this interrupt is set to enabled your MCU invokes interrupt vector (ISR).
So, how to workaround this?
Short explaination:
Use one of interrupts given by timer unit and set "faster" than signal on input can change.
Probe input states in timer ISR.
Whenever condition is met, for example high-state on pin for about 5 ms, you can save that fact in variable value.
Make callback to execute action or just make action inside your ISR, that depends about execution time of this action, ISRs should be short in execution time.
Pseudocode below (typed without compiling, just here in answer textbox):
#include <avr/io.h>
#include <avr/interrupt.h>
volatile int sth_happened = 0;
void ExecuteCallback(void)
{
// your action goes here
// reset sth_happened by assgining to 0
}
ISR(TIMER0_COMP_vect) // this ISR should be executed faster than signal on chosen pin can change
{
// check PIN of your pin here
// if state/signal on your pin met requirements,
// save it to variable or execute another code
// sth_happened = 1 / ExecuteCallback();
}
int main(void)
{
// Prepare your ISR timer here
// I would recommend to use CTC mode with desired execution time
sei(); // enable interrupts
while(1)
{
if (sth_happened) ExecuteCallback();
}
return 0;
}
You might consider just making the main loop in your program run faster so you can read those pins in your program and react when they change.
If you really need actual interrupts, you might consider switching to a newer AVR like the ATmega328P, where every I/O line can be used as a pin-change interrupt (PCINT) pin.
Related
As the title says its not giving me any errors when i build and run in code composer, but nothing happens on the baord. It even says the normal : "MSP430: Flash/FRAM usage is 84 bytes. RAM usage is 80 bytes." The code is below, should just light up leds in pattern. Straight from textbook, tried other code also.
#include <msp430.h>
void main (void)
{
WDTCTL = WDTPW | WDTHOLD; // Stop watchdog timer
P2DIR = 0x18; // Set pins with LEDs to output, 0b00011000
P2OUT = 0x08; // LED2 (P2.4) on, LED1 (P2.3) off (active low!)
for (;;) { }
}
`
The compiler tells you how many bytes you code needs from the Flash and RAM Memory. But this output does not mean that, those byte have also been transfered to the chip.
So perhaps the easy answer is: After compiling the code you have to start the debugger which automatically transfers the programm to the chip's flash memory and starts it.
If you had done this already then, it could be possible that:
you have not chosen the right serial port (virtual USB to Serial?)
your driver (flash programmer over usb) is corrupt (Windows ?)
your MSP430 is RIP
if you use a lauchpad:
your lauchpad is damaged (especially the USB programmer part)
you removed the jumper that connect the USB Programmer with the chip' UART programming pins.
What is the difference between INTDisableInterrupts() and INTEnableSystemMultiVectoredInt() and asm volatile ("di")
In Pic32, there are "normal" interrupts and "Vectored" interrupts. If you aren't familliar with Pic32, "vectored" means that each interrupt has it's own interrupt handler function. You can have a function for UART interrupt and another function for RS232 (UART),...
You do not have to put everything in a 'high priority' and a 'low priority' interrupt anymore.
So :
INTDisableInterrupts() will simply disable the interrupts. This will call "di".
"di" : simply disables the interrupts, in assmebler.
INTEnableSystemMultiVectoredInt() will let tell your PIC32 to use a different function for all your interrupts. If you did not provide interrupt handler functions for each of your interrupts, then it will seem as if they are disabled. Your interrupts are NOT disabled however, and if you write an handler for an Vectored interrupt, your pic will use it.
UPDATE:
#newb7777
To answer your question :
If you have only one interrupt ( not vectored ), then you have one big function that must check all the "Interrupt Flag register" to know what caused the interrupt and process the right code.
If you have 'vectored interrupts', then the PIC behaves like most processors ( they almost all have vectored interrupts ). When something happened that would generate an interrupt then a register changes value. For instance one that would be called "UART_1_Rx_Received". Before executing an instruction, the processor sees that this flag is on and if the 'Interrupt enable register' and the 'global interrupt enable register' are both ON, then the interrupt function will be called. Note that all interrupts also have a priority. If a high-priority interrupt is running then it will never be interrupted by an interrupt with <= priority. If a low priority interrupt is running then a higher priority interrupt could interrupt it.
However, you should not lose interrupts because if a byte comes from the UART that would generate a low-priority interrupt and a higher-priority interrupt is running, then the flag will still be set. When the higher priority interrupt ends, then the lower priority will be executed.
Why do we disable interrupts then ? The main reasons to disable interrupts are:
- the interrupt changes the value of a variable. if the code loops :
for(i=0;i==BufferSize;i++)
and your interrupt changes the value of BufferSize while this loop executes, then the loop could execute forever (if BufferSize changes from 100 to 2 while I has the value 99 then I will not get back to 2 for a long time...). You may want to disable interrupt before doing the loop in that case.
Another reason could be that you want to execute something where timing is important.
another reason is that sometimes, MCU needs you to execute a few instructions in a specific order to unlock something that would be dangerous to execute by error so you don't want an interrupt in the middle of the process.
If you have a circular buffer that received bytes from an interrupt and you pool that buffer from the code then you want to make sure to disable interrupts before removing a variable from the buffer to make sure the variables don't change while you read them.
There are many reasons to disable interrupts, just keep in mind that you can also create a "volatile" variable for global variables that are used in and outside of interrupts.
One last thing to answer your question : if you get an interrupt for every byte that comes in your UART at 115,200 baud, and you have an interrupt function that takes a long time to execute, then it is possible to miss a byte or two. In that case if you are lucky there is a hardware buffer that allows you to get them but it is possible also that there isn't and you would lose byte in your communication port. Interrupts must always be as short as possible. When possible, set a flag in the interrupt and do the processing in your main loop outside of the interrupt. When you have many interrupt levels, always use high priority for interrupts that could trigger often and low priority if an interrupt processes for a long time.
I've recently been playing around with the ATtiny85 as a means of prototyping some simple electronics in a very small package. I'm having a spot of trouble with this since the language used for many of its functions is very different (and a lot less intuitive!) than that found in a standard Arduino sketch. I'm having some difficulty finding a decent reference for the hardware-specific functions too.
Primarily, what I'd like to do is listen for both a pin change and a timer at the same time. A change of state in the pin will reset the timer, but at the same time the code needs to respond to the timer itself if it ends before the pin's state changes.
Now, from the tutorials I've managed to find it seems that both pin change and timer interrupts are funnelled through the same function - ISR(). What I'd like to know is:
Is it possible to have both a pin and a timer interrupt going at the same time?
Assuming they both call the same function, how do you tell them apart?
ISR() is not a function, it's a construct (macro) that is used to generate the stub for an ISR as well as inject the ISR into the vector table. The vector name passed to the macro determines which interrupt it services.
ISR(INT0_vect)
{
// Handle external interrupt 0 (PB2)
...
};
ISR(TIM0_OVF_vect)
{
// Handle timer 0 overflow
...
};
According to the datasheet ATtiny85 doesn't have the same interrupt vector for PCINT0 and TIMER1 COMPA/OVF/COMPB, so you can define different ISR handlers for each one of them.
If you're using the same handler for more interrupts, it might be impossible to differentiate between them, as interrupt flags are usually cleared by hardware on ISR vector execution.
As an addition to the accepted answer:
Is it possible to have both a pin and a timer interrupt going at the same time?
The interrupt can occur at exactly the same time on the hardware level and the corresponding interrupt flags would be set accordingly. The flags indicate that the ISR for the respective interrupt should be executed. But the actual ISRs are (more or less obviously) not executed at the same time / in parallel. Which ISR is executed first (in case multiple interrupts are pending) depends on the interrupt priority, which is specified in the interrupt vector table from the data sheet.
I'm using HAL drivers with code generated by CubeMX. In main routine I called HAL_UART_Receive_IT(). After transmitting data over UART (which is connected in a loopback fashion) I can see the module is receiving byte and setting RXNE bit in registers. However interrupt is not generated? I can't explain why... In HAL_UART_Receive_IT() function there is code enabling interrupts, so what's wrong?
You are not giving enough info and code in your question.
Anyway, in your stm32xx_hal_msp.c file you initialize your peripheral from hardware point of view: be sure to enable interrupts too
HAL_NVIC_SetPriority(USART1_IRQn, 0, 1);
HAL_NVIC_EnableIRQ(USART1_IRQn);
Then add
void USART1_IRQHandler(void)
{
HAL_UART_IRQHandler(&huart1);
}
to your stm32xx_it.c file
Background:
I am using a cortex-M3 ARM core without an OS.
My main loop waits for a flag from an interrupt handler and then executes a function doBigTask().
Within a separate interrupt handler, I want to execute another function doSmallTask(), but since this function is also non-trivial, I still want other I/O related interrupts to be handled.
My Question:
Are there any issues with simply enabling interrupts from within doSmallTask()? For example, are there any complications with exiting an interrupt handler after interrupts have already been disabled?.
Note: I'm not expecting a re-entrant interrupt to occur as doSmallTask() will finish well before the next interrupt triggers it.
int flag = 0;
void doSmallTask()
{
asm volatile ("cpsie i"); // Enable interrupts
// do rest of function
// ...
}
void irqHandler1()
{
flag = 1;
}
void irqHandler2()
{
doSmallTask();
}
void irqHandler3()
{
// service I/O
}
int main()
{
while(1)
if (flag)
{
doBigTask();
flag = 0;
}
}
First of all, your "flag" variable should be volatile since it is shared between foreground and background code.
But to answer your question, on the Cortex-M, interrupts are already enabled inside an ISR. This is to support interrupt nesting. Inside an ISR, only interrupts of a higher priority will interrupt / preempt the current ISR. So it's very important that interrupt priorities are configured properly.
Read up on the Cortex-M family's NVIC for more information. Note that the interrupt sources, and the number of supported interrupt priorities, are dependent on the silicon vendor. In theory up to 240 external interrupts are supported, in reality it's typically much less.
There was a recent blog post about ARM Cortex M interrupt priorities that explained this in more detail.
You may change the interrupt priority. Set the priority of the irqHandler2 smaller then others.