External interrupt flags on pins D1 and D2 (INT_vect) and (INT1_vect) of an uno can be cleared using EIFR, for example EIFR=1 clears the flags on pin D2. This is especially useful if you've got say an incoming signal on D2 which changes as the signal comes in and then wiggles about for a bit, and you only want the interrupt to happen when the incoming signal begins and not be triggered again every time the line changes. Are there any equivalents of EIFR with which to clear the flags associated with, that is to say EIFR equivalents which do the same thing but for TWI_vect and/or ADC_vect instead of for INT0_vect or INT1_vect. I've got some interrupts triggered by TWI_vect and ADC_vect and would like to clear the EIFR equivalent flag when they start. I have ctrl+f 'd the atmega328p datasheet for EIFR but when I searched around it, close to every incidence of "EIFR" in it's text I saw no mentions of ADC or I2C interupts.
Thanks
Well, if you are dealing with TWI, then you will need to clear the TWINT flag, not the EIFR flag. Look at the TWI section of the datasheet. (or read through the Wire library code to see how it is implemented)
Same is true for ADC
@OP
1. If you want to enable/disable TWI interrupt, you have to play around with TWIE bit of the TWCR Register.
2. If you want to enable/disable ADC interrupt, you have to play around with ADIE bit of the ADCSRA Register.
3. If you want to enable/disable external interrupts (INT0, INT1), you have to play around with INT0 and INt1 bits of EIMSk Register.
Thanks for your answers, but as far as I can tell ADIE and TWIE, which I've already ben using enable and disable the interrupt. What I'm after is something that clears the memory flags whih say "execute this interrupt when you can". ADIE and TWIE are, as far as can tell, the equivalents of attaching and detaching the external interrupt pin interrupts (just like EIMSK does), not the equivalents of EIFR.
Infraviolet:
Thanks for your answers, but as far as I can tell ADIE and TWIE, which I've already ben using enable and disable the interrupt. What I'm after is something that clears the memory flags whih say "execute this interrupt when you can". ADIE and TWIE are, as far as can tell, the equivalents of attaching and detaching the external interrupt pin interrupts (just like EIMSK does), not the equivalents of EIFR.
When there is an 'interrupt triggering signal', the corresponding 'interrupt flag' becomes active.This 'interrupt flag' generates 'interrupt request signal (IRQ)' for the MCU should the corresponding 'interrupt (local) enable bit' and the 'global interrupt enable bit' are at 'active states'.
Before going to the Interrupt Sub Routine (ISR), the MCU disables the 'global interrupt enable bit' so that the MCU is not interrupted until the current ISR via complete. (The individual local interrupt enable bit (s) are not disturbed.)
While the MCU vectors to the ISR (in vectored interrupt process), the 'interrupt flag' is automatically cleared so that the MCU can detect the next 'interrupt triggering signal' after resuming the Mainline Program.
If 'vectored interrupt' is not desired (in polled interrupt process), the user must clear the 'interrupt flag' manually by executing codes.
Sorry, but that still doesn't answer my question. EIFR is a flag which says specifically whether interrupts on the D2 or D3 pins have occured, it holds this information long enough for an interrupt to sart and even during the interrupt EIFR itself may be changed if a triggering event happens while the interrupt is running. If such a triggering event does happen during the interrupt then after the interrupt ends the processor sees that EIFR has been set and starts off another run of the interrupt, albeit with a guaranteed execution of 1 line of main code before the second interrupt starts. If you have an interrupt triggered by a change on D2 or D3 which is then followed by noise on D2/D3, lets consider a case where the interrupt runs for longer than the nosie lasts. While the interrupt occurs you might set a "no interrupt triggers have happened" value of EIFR at the end of your interrupt so as to ensure that the noise during the interrupt which would have set EIFR to say "when this interupt finished run it again" doesn't cause another copy of the interrupt to run just afetr it has run once. EIFR is not the same as EIMSK, EIMSK says whether the processor should or shouldn't trigegr interupts when the EIFR flag gets set. EIMSK enables or disables these interrupts, EIFR records whether interrupt triggering events have actually happened. I know that for the interrupts which are not D2 and D3 pins (for example ADC_vect and TWI_vect) other things are used to enable and disable the interrupts, ADIE and TWIE respectively. These are the ADC and I2C equivalents of EIMSK. But what are the ADC and I2C equivalents of EIFR, the thing which doesn't enable the interrupt but does register whether interrupt events have occured?
Infraviolet:
But what are the ADC and I2C equivalents of EIFR, the thing which doesn't enable the interrupt but does register whether interrupt events have occured?
1. For ADC Interface; it is the ADIF flag which becomes active when conversion is complete. This flag can interrupt the MCU.
2. For TWI Interface; it is the TWINT flag which can interrupt the MCU.
