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'[PIC:]Rocket camera timer'
2004\04\19@171630 by Mike nicholas

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I'm currently building a mid sized camera rocket using a Kodak F-350 aps
camera, it has an electronic shutter. I will be using two switches the first
will engage very shortly after ignition and the second will make momentary
contact when the chute opens.

 The first switch will start a program where a 1/2 second pulse will be
triggered every 1.5 seconds for a total of 5 pulses then when the second
switch engages the first program is bypassed and a second program starts a
1/2 second pulse every 5 seconds for a total of 5 pulses, then the chip
shuts down regardless of any input.

I'm very new with programming and have only programmed one pic with the
blink program and it didnt work once put in the circuit, I have a few
pic16F84A and have some 12F675 comming in soon. I have quite a bit of
electronic knowledge, but programming is greek to me.

Anything that would help would be great
Mike

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2004\04\19@172915 by Matt Marsh

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> I'm very new with programming and have only programmed one pic
> with the blink program and it didnt work once put in the circuit,
> I have a few pic16F84A and have some 12F675 comming in soon. I
> have quite a bit of electronic knowledge, but programming is
> greek to me.

Maybe you should try and get your blink program working first? There
are lots of great folks on here and I'm sure that they'll help you
get it working... (I'll try myself, but I'm a bit of a beginner
too!). I learnt so much by getting my first program working...

Matt

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2004\04\19@180732 by Mike Hord

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This is a fairly simple project, so I don't think you'll have too much
trouble.

First, check the following site:
http://www.voti.nl/swp/index.html

The gentleman who authored it frequents the mailing list.

Second, get the blinking circuit to work!

Third, here's my approach:

Use a 12F675 (since you have them).  Run it with a 32.762 kHz crystal,
since many are built to be sturdy and that's important.

Use busy loops to wait the appropriate number of cycles (.5 sec is 4096
cycles).  Ta-dah!  Accurate to 20 ppm, and probably costs less that $2.

If you need less accuracy, you can do it using the internal oscillator...

Mike H.

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2004\04\19@181807 by David VanHorn

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>
>I'm very new with programming and have only programmed one pic with the
>blink program and it didnt work once put in the circuit, I have a few
>pic16F84A and have some 12F675 comming in soon. I have quite a bit of
>electronic knowledge, but programming is greek to me.

As someone who has put computers in rockets before:  Avoid crystals.
Internal R/C oscillator, or external resonator is a much better choice.
Xtals are internally fragile, and they don't like high accelerations.
If you can keep the long axis of the crystal in the thrust line, they do a little better, but it's not worth it.

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2004\04\19@184333 by Jinx
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>   The first switch will start a program where a 1/2 second pulse

As Matt Marsh has said, you really ought to get the chip working
first otherwise any programming you do has got nowhere to go

----------------------------------

This is fairly simple in-line code that doesn't use interrupts. Not
glamorous at all, but it's a pretty straight-forward job that doesn't
require much sophistication. Note that it's untested and commits
the PIC entirely to looping, which would not be the case if you used
interrupts. But it's simple and hopefully you can follow it well enough
to be able to build on

Note also that "status,z" is not how most people would use the Zero
flag, but it's clearer for you. It can be defined

#define  zero   status,2  ;or status,z

or tests made into macros, for example

skpz     macro                ;skip next if Z=1
        btfss status,2
        endm

MPLAB also allows the use of the BZ and BNZ branch instructions

Anyway.......

The timing of this is based on a 32.768kHz crystal, no pre-scaler,
which will make TMR0 rollover 32 times / sec = (32768/4)/256

The 12F675 has a 16-bit TMR1, but the F84A doesn't. The F628
(F84A replacement) does too, but it hardly matters in this case.
There are many ways to do what you want, this is just one. If you
did use a 16-bit timer, then a /8 prescaler would produce 1/4s
roll-overs, which would simplify the code. /16 is available for TMR0
to get 1/2s rollovers

A couple of things you didn't specify. Are the switches toggle or
momentary (you may need to test for switch release) and is the
first timing period a pulse or a gap ?

This code will do (pulse-space) x 5, repeat with modifications
to do the second part

         clrf   tmr0         ;initialise TMR0
         movlw  .5           ;initialise pulse counter
         movwf  pulse_cnt
         clrf   ro_cnt       ;initialise rollover counter

         btfss  switch1      ;wait for switch closure
         goto   $-1
         bsf    pulse        ;set output high initially

;hold pulse on for 1/2 second

wait1     btfss  intcon,t0if  ;wait for TMR0 rollover
         goto   wait1
         bcf    intcon,t0if

         incf   ro_cnt       ;increment rollover count
         movlw  .16          ;test if = 16 = 1/2 second
         xorwf  ro_cnt,w
         btfss  status,z     ;yes (zero flag = 1 = match)
         goto   wait1        ;no
         bcf    pulse        ;set output low

;wait for 1 second

         clrf   ro_cnt       ;reset rollover counter

wait2     btfss  intcon,t0if  ;wait for TMR0 rollover
         goto   wait2
         bcf    intcon,t0if

         incf   ro_cnt       ;increment rollover count
         movlw  .32          ;test if = 32 = 1 second
         xorwf  ro_cnt,w
         btfss  status,z     ;yes
         goto   wait2        ;no
         clrf   ro_cnt       ;reset rollover counter
         decfsz pulse_cnt    ;bump pulse counter
         goto   wait1        ;not done, repeat

;Part 2

         btfss  switch2
         goto   wait2

etc

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2004\04\19@194644 by teven Kosmerchock

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Mike,

Check out http://www.xavien.com, they sale a nifty camera timer, I should
know I designed it ;-). It even uses a PIC12C508A......

You can download the users manual to see the functions.

Best regards,
Steve


>>> spamBeGonemrgizmospamBeGonespamVIANET.CA 4/19/2004 5:08:10 PM >>>
I'm currently building a mid sized camera rocket using a Kodak F-350
aps
camera, it has an electronic shutter. I will be using two switches the
first
will engage very shortly after ignition and the second will make
momentary
contact when the chute opens.

 The first switch will start a program where a 1/2 second pulse will
be
triggered every 1.5 seconds for a total of 5 pulses then when the
second
switch engages the first program is bypassed and a second program
starts a
1/2 second pulse every 5 seconds for a total of 5 pulses, then the
chip
shuts down regardless of any input.

I'm very new with programming and have only programmed one pic with
the
blink program and it didnt work once put in the circuit, I have a few
pic16F84A and have some 12F675 comming in soon. I have quite a bit of
electronic knowledge, but programming is greek to me.

Anything that would help would be great
Mike

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2004\04\19@200759 by Jake Anderson

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I have made a camera timer to do pretty much exactly that

take a look at
http://www.robowars.org/teams/plan-b/Doonside%202003-06-28/

if you need help feel free to email me

grooveee
place the atsymbol here
optushome
.com
.au

MUHAHAAH choke on that spambots

some general advice
find out how the camera triggers
ie for the camera I used it is active low inputs on its switches so
triggering was easy.

if your going to get a chip the 16F628A is a good one to get, the internal
oscilator is a handy thing and good enough for what you want to do there
(though all mine run at 20Mhz cos its just more fun ;->) and the built in
USART makes debuging easy

only experiment on and fly with a camera you dont mind recovering with a
shovel.

take a look at JAL it makes programming pretty easy for most things.
{Original Message removed}

2004\04\19@204735 by redtock8

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Jake,
how did you interface to the camera?
I would like to do this

Al

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2004\04\19@210020 by redtock8

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Sorry, found it.

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2004\04\19@210813 by Jake Anderson

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its all fairly well documented in the draft assignment on that page i
believe

basically the camera runs on 3.3V with the trigger and the buttons on the
beack being active low inputs.

the pic i was using was running on 5V
basically all i did was set the pins that drove the camera to inputs (use
the schmit trigger pins so there is no smoke) then set their outputs to low
(while they were still set to input) then to trigger i made the pins outputs
for a little while. ie pulling the cameras circut to ground.

that was how my specific camera worked


{Original Message removed}

2004\04\19@211435 by redtock8

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Thanks

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2004\04\19@234614 by Mike nicholas

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Thank you, I will start with the simple blink and work my way up, if I have
problems after my next attept I will ask for help.
{Original Message removed}

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