12f675_fuse_about_to_blow!

[LEDave]

Hi everyone.

I'm working on my first circuit using the12F683 and I'd like to add a push button as an input. Would I be right in assuming that:

A pull-up resistor say 10k from the +5v line onto the chosen input GPIO.n and a push button connected from GPIO.n to ground should do the job?

This to my mind would leave GPIO.n at +5v until pressed, momentarily dropping to 0v.

David

[mackrackit]

Yup, that will work.

[LEDave]

Cheers mackrackit.

My project, here's the master plan:

I'm going to use the 12F683 to output 4 bit words to drive a BCD to 7-segment decoder driver: Count up from 0-9 in a continual loop IF the push button is pressed THEN GOTO countdown from 9-0 in a continual loop, IF pressed again count down from 5-0 then stop.

This project covers a lot of the ground we've been over in the last week or two and would give me some much needed practical practice.

Another question: Is this program statement viable / do-able to provide input words into the decoder driver?

i VAR WORD
Main:
For i = 0 to 3 etc
LOOKUP i, [0, 1,2,3], GPIO
NEXT i

Sorry but the code tags didn't work tonight.

This would output from the PIC (I hope):

0000 making the driver display '0'
0001 " " '1'
0010 " " '2'
0011 " " '3'
1000 " " '4'

Also from the output side of the PIC ('words') to the input side of the display driver, I'd like to bleed off a little current to the base of four transistors with LED's in the collector leg to visually see the binary count, just for fun.

So what do we think then guys? Have I learned my lessons well, or am I heading for the books...!

David

[HenrikOlsson]

Hi David,

i VAR WORD
Main:
For i = 0 to 3 etc
LOOKUP i, [0, 1,2,3], GPIO
NEXT i

That will work for exercise purposes but in the above case there's really no need for the LOOKUP table. You can just as well write i directly to GPIO, you'd also want a PAUSE in there or it will count really fast, and don't forget to set the TRIS-register to make the pins in question outputs:

Main:
For i = 0 to 3
  GPIO = i
  Pause 500
NEXT i

0000 making the driver display '0'
0001 " " '1'
0010 " " '2'
0011 " " '3'
1000 " " '4'

Not quite, it will count (and display) 0, 1, 2 and 3 since 3 is what you have in your FOR statement. Actually i will get incremented one more time, to 4, but when that happens the code will jump to after the NEXT statement so the "4" will never make it to GPIO. (If that last thing didn't make sense never mind, the important thing is that it counts from 0 to 3.)

/Henrik.

[LEDave]

Hi Henrik

So to get the program to count down from 9-0 would this do it:

FOR i = 9 to 0 STEP -1
GPIO = i
Pause 500
NEXT i

*I don't know why but I my code tags still aren't working tonight, sorry*

If GPIO = 9 then out would go 1001 to the driver etc...

Yes, without the pause it would have counted to 3 lightning fast I guess.

The LOOKUP table is excellent for outputting stored values though, really glad we touched on it.

[HenrikOlsson]

Hi,
Yes, that is correct - all of it. Good job!

All BBTags uses square brackets, ie. [...] and [/...] to turn the option ON and OFF respectively. Seems to work from here. There's a box at the bottom of the page showing if BBCode is ON or OFF, make sure it's ON.

/Henrik.

[LEDave]

Henrik thanks for that.

I'm trying to use the COUNT command that mackrackit put me onto to jump from one loop to the next after a button is pressed. There are three loops (count up to nine when button pressed once - Jump to second loop and count down from nine if button pressed a second time and to a final third loop, count down from five after button is pressed a third time).

Is this code anywhere near to where I need to be? If I'm close but not quite there please let me carry on thinking. If I'm miles off course then a pointer would be much appreciated.

COUNT PIN.n, 10000, VAR B_P_C WORD  'Set GPIO.n as input, define Button Push 
Count as VAR WORD B_P_C, with a loop count time of 10 secs.

Let i = B_P_C

IF B_P_C = i GOTO  FIRSTLOOP ' Button pressed once
IF B_p_c = i+i GOTO SECONDLOOP ' Button pressed twice
IF B_P_C = i+i+i Goto THIRDLOOP   ' Button pressed a third time

My code tags are working today, I didn't touch anything.

David