Instant Interrupts - Revisited

[HankMcSpank]

mister_e.... I'd like to get interupts working on my 16F690 ....I visited Darrel's website & on the very first example "Hello World", he shows the code along with a short schematic - the interupt is showing as being presented on port RBO (actually called RBO/INT on the diagram).

I have some (newbie!) questions...

Are Darrel's interput routines for a specific PIC?

I ask because my PIC 16F690 doesn't even have an RB0(!), therefore to my next question....

Is there a particular PIC pin I should be using for his routines to work.

My end goal is quite simple...I have an encoder wheel with 48 black stripes that I'm having one helluva job getting the polling right....I'd simply like to be able to use a PIC interupt for when each black stripe passes the photo transistor 'pickup' (to increment a PIC counter)

That said, for testing puproses I do need one more interupt ...this being for a magnetic switch (I've glued a magnet to the edge of the disc so I know when the wheel has turned once) to interupt once per rev, I can then make sure that the PIC 'saw' all the stripes for the past rev....so to my other question - is there normally just one INT pin that's useable for externally triggered interupts on a PIC (specifically a 16F690)

i'd dearly love to be able to use Darrel's simple routines...but I'm a little clueless wrt ensuring I'm connecting my incoming 'pulses' to the correct PIC 16F690 pins!

edit: Darrel has kindly replied to the earlier PM I sent him, telling me that I need to look for the pin marked 'INT'...which on my PIC 16F690 is apparently pin RA2 - tks Darrel!

[Jumper]

Hi,

If you have a T?CKI pin on your pic you can use that pin to check for black stripes. This is the pin for the external clock signal connected to the internal timer/counter. This way you can get an interupt every black stripe or every 2:nd or once per wheel rotation (or anything else more or less). This is all depending of what you preload the counter with. If you have a 8-bit counter and load FF into it, next clock pulse will overflow the counter and you will get an interupt. If you preload it with FF-(dec 48) it will overflow once every full rotation of the wheel.

If you just want to count the stripes preload it with 0 and off you go....

This way your PIC will do most of the counting by itself and giving you more instruction time for something more useful.

If you use the RA2/INT for the magnetic switch you can use RA5/T1CKI the external clock input for the stripes phototransistor

/me

[HankMcSpank]

Hi,

If you have a T?CKI pin on your pic you can use that pin to check for black stripes. This is the pin for the external clock signal connected to the internal timer/counter. This way you can get an interupt every black stripe or every 2:nd or once per wheel rotation (or anything else more or less). This is all depending of what you preload the counter with. If you have a 8-bit counter and load FF into it, next clock pulse will overflow the counter and you will get an interupt. If you preload it with FF-(dec 48) it will overflow once every full rotation of the wheel.

If you just want to count the stripes preload it with 0 and off you go....

This way your PIC will do most of the counting by itself and giving you more instruction time for something more useful.

If you use the RA2/INT for the magnetic switch you can use RA5/T1CKI the external clock input for the stripes phototransistor

/me

Thanks...there's some top tips there.

Just a thought here - is it even possible to get reliable results with mechanical switches & interupts?

By this I mean, a mechanical switch normally needs a debounce, else you'd get more than one interupt for every time the switch 'settled'? In my situation, it's importnat that there's just one 'trigger' for every revolution of the encoder wheel (so I can establish how many interupts/black stripes the PIC has counted over one rev)...if I used an interupt for the magnetic switch, there'd be a possibility of not just one interupt...but several in quick succession...which will cause a bit of 'fog' whilst trying to confirm that my wheel, circuit & PIC are all in sync & counting 48 stripes per turn!

By the way...I've now dabbled with Darrel's "Hello World" which will suit my encoder wheel needs perfectly....after wrestling with 'pin' polling for weeks with my encoder wheel & getting very erratic results, I'm one very happy McSpank here today! October 05, 2002 maybe was a good day...but I can say without any shadow of a doubt, for me the 19 May 2009 was a lot better !!

Just a couple of small suggestions for Darrel's website (to save avoid a lot of newbie-esque puzzlement) - on Darrel's very first hello world code page, it might be worth saying that a user will need to establish their own PIC variant's 'INT' pin, along with perhaps a couple of PIC specific examples. (it might be ovbious to you old hands, but looking at the plethora of pins PICs have, it wasn't obvious to me!)

Also, for what it's worth...the 16F690 is perhaps the most common chip that newbies come into contact with at the moment (on account it's bundled with Microchip's very popular PikKit2 starter kit)...I had a problem with Darrel's "Hello World" code when I first compiled ...."error: variable wsave3 position request 416 beyond ram_end 367.", ultimately meaning a line in Darrel's DT_INTS-14.bas file needed commenting out - that might also be worth a mention too? (or at least some mention on a FAQ page?)

Anyway, a hearty thanks to Darrel... without his effort towards making interupts easy with PICBasic , I'm sure I would have left interupts for another day (ie sometime in 2023!)

[jchandir]

I am using a 16f866 with your instant interrupt but I cannot get it to wake up from sleep using a USART RX int.. If i use a Pause 1 in the main loop it works fine but I would really like for it to go to sleep and just wait. Please let me know what I am doing wrong.. here is the code.. Thank you Darrel for the awesome instant interrupt routines.

Define OSC 8

INCLUDE "DT_INTS-14.bas"     ' Base Interrupt System
INCLUDE "ReEnterPBP.bas"     ' Include if using PBP interrupts

' Set receive register to receiver enabled
DEFINE HSER_RCSTA 90h 

' Set transmit register to transmitter enabled
DEFINE HSER_TXSTA 20h 

' Set baud rate
DEFINE HSER_BAUD 2400

x var byte
OSCCON=%01111000

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   RX_INT ,  _ToggleLED1,   PBP,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor
ENDASM

@ INT_ENABLE  RX_INT      

Main:
@sleep
@nop
GOTO Main

'---[RX-Int - interrupt handler]--------------------------------------------------
ToggleLED1:
hserin [x]
hserout ["Hello"]
@ INT_RETURN

[Darrel Taylor]

I assume you meant 16F886?

From the datasheet...

During Sleep mode, all clocks to the EUSART are
suspended. Because of this, the Baud Rate Generator
is inactive and a proper character reception cannot be
performed.

You can use the AUTO-WAKE-UP ON BREAK feature of the EUSART, but there are several things to consider.

Take a look at section 12.3.2 AUTO-WAKE-UP ON BREAK
<br>

[jchandir]

shoot.. i meant 16f688... sorry about my careless mistake.

[jchandir]

ok so i solved the problem. thanks Darrel. I just had to set the BAUDCTL.1 (WUE) bit.