What the heck am I doing wrong?

[andywpg]

I'm having some trouble figuring out something and hope someone here can help.

I am doing a project to control the marker lights on a pace car for a race track. We will have
strobes on the four corners and on the front of the mirrors, as well as four lights on the rear
that will indicate 'pass left', 'pass right' and 'do not pass'.

To that end, I have decided to use a 'time slice' scheme to control the lights. Based on switch
inputs, there will be word or long-sized 'patterns' of bits to turn the outputs on or off, then a pause
and move on to the next bit in the pattern.

My problem is figuring out how to shift the bits out of the patterns to turn the output ports on and off.

I had thought of using SHIFTRIGHT (>>) to shift the bits off the LSB end of the pattern to turn the
port on or off based on it being a one or zero, but it would appear that SHIFTRIGHT discards the shifted
bit and won't let it be used.

My other thought was to use an index to address the bits individually, but I don't think this will work
either. For example:




pattern var byte 'may be a word or even long in the actual program
index var byte

pattern = 01010101 'example pattern, not all will be this regular

for index = 0 to 7
PORTB.0 = pattern.index 'turn portb.0 on or off based on whether the bit is 0 or 1
pause 100
next index



For some reason, the 'percent' sign vanished - it's supposed to be 'percent' 01010101

I'm pretty sure that won't work either. What am I doing wrong? Any ideas how I can accomplish this? I know there
must be a way, I'm just missing it. Perhaps a 'bit array'? Is that even possible?

Thanks for any help,

Andy

[Demon]

Andy, I can't help you with your code. But if you click on the first icon above the editor box, two As, you want to be in SOURCE mode, not WYSIWYG.

Then this will always work:
%01010101


To set this by default, click on SETTINGS at top right, then GENERAL SETTINGS, then at Message Editor Interface, click on Standard Editor - Extra formatting controls.

Robert

[Art]

I had thought of using SHIFTRIGHT (>>) to shift the bits off the LSB end of the pattern to turn the
port on or off based on it being a one or zero, but it would appear that SHIFTRIGHT discards the shifted
bit and won't let it be used.

Maybe not the best way, but "pattern" can be the high byte alias of a word variable,
then when you shift it, the low byte will either be 00000000 or 10000000,
which is either zero or not zero.

[HenrikOlsson]

Hi,
Try something like

Pattern = %11001010
FOR index = 0 to 7
PORTB.0 = pattern.0[index] 'turn portb.0 on or off based on whether the bit is 0 or 1
pause 100
NEXT index

/Henrik.

[AvionicsMaster1]

Would a look up table work? Something like this:

starthere:
IF gpio.3 = 1 THEN GOTO main

GOTO starthere

'------------------------------------flash them all to make it look cool
main:
FOR i = 1 TO 20
RANDOM myword
mybyte = (myword//20)
IF previous_random = mybyte THEN GOTO main
GOSUB high_led
PAUSE delay
gpio = %000000
PAUSE delay
previous_random = mybyte
NEXT i

gpio = 0
trisio = %111111
' ----------------------------------------------------send it back to nap
GOTO starthere

high_led:
LOOKUP mybyte,[%000001,%000010,%000001,%000100,%000001,%010000,%0 00001,%100000,%000010,%000100,%000010,%010000,%000 010,%100000,%000100,%010000,%000100,%100000,%01000 0,%100000],gpiostate
gpio = gpiostate
LOOKUP mybyte,[%111100,%111100,%111010,%111010,%101110,%101110,%0 11110,%011110,%111001,%111001,%101101,%101101,%011 101,%011101,%101011,%101011,%011011,%011011,%00111 1,%001111],tristate
trisio = tristate
RETURN

END



I cut this out of a program I was using to control 20 LEDs so you'd have to modify the table to suit your needs.

[andywpg]

That worked, thanks!

[andywpg]

I think this would work too - thanks! It amazes me how many ways there are to do the same thing.

[Demon]

Wait, there's more, the brainiacs will post assembler solutions now. :D

Robert

[andywpg]

Wait, there's more, the brainiacs will post assembler solutions now. :D

Robert

Actually, before I saw Henrik's method, I came up with ANOTHER solution that worked too. I used byte-sized arrays. It worked great, only it used 160 bytes of 367 bytes of total RAM available. Using arrays the way Henrik showed me (same thing, only on the bit level) it's only a few bytes.

Before I came up with the byte array solution, I was toying with an assembler subroutine that used BTFSC f,b (if bit 'b' in register 'f' is a one, the next instruction is executed, otherwise skipped).

So I would have tested the bit, then next instruction would branch to a routine that set the light on, the instruction after would set the light off.

I just KNEW that PBP would be able to do it though.

The best part? The dang program worked first try! Only a couple of syntax errors to clear up, but IT WORKED! Tested everything on a breadboard, now all I have to do is build it in a box and make it look pretty......

Thanks for all the help!

Andy