Hi all, New to this forum in a posting perspective but it's been a great help in a lot of areas from the start of my 8051 classes this year and last year so for that thanks. Im coming near the end of my final year project and I'v come across a slight problem with my interrupt implementation. I have RTFMed about all I can find on interrupts from any number of sources before you tell me to Please read the manual. The problem is that my ISR is triggered fine the first time sets a flag goes back carries out a function ... due to it not being a good idea to have function calls within an ISR ... resets flag and then sits reading the clock again however when I try to interrupt again it will not carry out the ISR this next time.
I have : reset external interrupt flag; reset condition variable flag; even attempted to re-enable external interrupt (even though this is probably not required);
The code is a long one so Id rather not post the entire thing here if anyone wants to take a look at it who has a good idea as to what I'm doing wrong or if anyone wants to suggest a specific part to post to look at the ISR or the menu its being called from please contact me. I will however not be sending this code on to anyone who's just looking for something to copy as I've read the manual to get it this far. I'd also be very happy to have someone look over the code in general for bad programming implementation if they would ... I'm a student in this subject but I've a keen interest in the field.
Also I'm Irish but this website is picking me up in America for some reason ?
Regards Robbie.
Apologies it seems I missed one of the tabs. Does the enable_interrupt need to be used after resetting the external interrupt flag some say yes and other implementations don't seem to require it. Thanks in advance.
What do you think that does??
What do I think what does ? If you mean the enable_interrupt I have it defined to set EA high which is what I needed to do to enable me to skip the first RFID scanned as intended. Im sorry I'm not sure what you mean ?
The text of my post refers to the title of that post; viz,
card_id[2,3,4,5,6,7,8,9,10,11,12,13] == kitef[0,1,2,3,4,5,6,7,8,9,10,11]
What do you thing that does??
Sorry only saw what you were referring to in the heading there. What I'm doing there is comparing from the 2-13 element of the scanned array to the 0-11 elements of a predefined RFID tag I've debugged this part of my code over a week and it does in fact compare each element to its opposing element and do exactly as intended.
No, in fact - you're not.
The 'C' programming language does not have any such way to compare multiple array elements
Time to revisit the 'C' text book!
Hint: look up the comma operator...
Ah bugger ... Well I'm kind of confused then I'm not sure how the if statement is working then as its able to differentiate between about 15 different tags I'm using. With some tags the first number elements are exactly the same as others and with others they are completely different.
Ah ha ! Thanks for that, that could have been embarrassing. Ok i'll have to rewrite that just a tad :p. Any chance you can see any such silly mistakes in the ISR and my implementation of it taking that the ISR is working for a comparison of the final elements of the listed arrays. I want to get this part working before I tackle the problem of comparing the complete tag ID as it is the more important at the minute.
Thanks again so here is my resolution to the aforementioned error you pointed out:
unsigned char i = 0; receive(); writecmd(0x99); if (card_id[13] == kite1[13]) { for (i=2;i<14;i++) { check=card_id[i]-kite1[i]; errors = errors + check; } if (errors != 0) { writedata('E'); writedata('R'); writedata('R'); writedata('O'); writedata('R'); writedata('!'); } else { kite1_f = 1; delay(10000); IE = 0; } }
Can you see any problems with this ?
And any input on the ISR as a whole problem would be a big help.
Yes:
check=card_id[i]-kite1[i]; errors = errors + check;
'check' could be positive or negative - so errors could "cancel-out"...
You test fails as soon as any mismatch fails - so you just need to flag that a mismatch was found (and there's no need to continue the loop beyond that).
Also, you are checking at the same index in each array - which isn't what your original code intended...
What I mean is, you need to construct a test that will indicate "fail" if any mismatch is found.
Ah how did i not see that thanks! ... I'll start work on that now .... The system I'm using has a maximum of 12 tags that are all predefined I've used tags that all have the final array differing from one another (hence how I thought it was doing the original implementation) so this is the starting check to differentiate between each tag and the check is then ensuring that the user is not cheating by using a different tag not predefined for usage in the orienteering course.
Any thoughts on why my ISR is only being triggered once ?
If your ISR is expected to trig by an external-interrupt pin, then you shouldn't also have any "receive()" in that interrupt.
Create a UART ISR that trigs, picks up single characters and places in a queue.
Then have other code consume characters from this queue to try to figure out if you have a complete code. Obviously taking into account incomplete transfers where the UART doesn't get a complete number for some reason and might later restart a new transfer.
If your RFID unit sends digits and ends the stream with a newline character, then you could have your serial code set a flag when it sees the newline, and the main loop reacts to the flag, scans the received data and accepts/rejects.
Too much data before the newline? Throw away all characters until you either gets a longer pause or a newline character.
Long pause after digits but before a newline? So timeout the received data and wait for a new transfer.
But don't try to do too much in an interrupt handler.
receive(); what does that do?
Right so in reply to Andrew(hope you don't mind me using your first name) I have changed the check to this:
if (card_id[13] == kite1[13]) { for (i=2;i<14;i++) { if (card_id[i]!=kite1[i]) { writedata('E'); writedata('R'); writedata('R'); writedata('O'); writedata('R'); writedata('1'); return; } } kite1_f = 1; delay(10000); IE = 0; }
Hope thats a bit better, kind of quickly thrashing out code here maybe I should take some time with the problem ?
In reply to Mr Westmark : Hello there and thanks would I be correct in assuming when you are talking about placing in a queue you are talking about an array or is there some other construct for this implementation? I'll show you my current recieve(); function below but it appears that my function is currently working for the first external interrupt but then failing to trigger in the second instance however from my debugging I can see its not sticking inside the ISR just not recognising it. Also go easy on me when you see this recieve function as it was the first time I wrote anything for serial communication.
void receive() //Function to receive data serialy from RS232 { unsigned char k; for(k=0;k<14;k++) { while(RI==0); card_id[k]=SBUF; RI=0; } }
memcmp()