turn on and off 21 LEDs using BStamp2 P40

Markus

Hi,

I can't turn on 21 LEDs using this rutine.
Do you know why ? Any easy rutine instead this one?

' {$STAMP BS2p}
' {$PBASIC 2.5}

ini:

FOR W2 = 0 TO 21
HIGH W2
PAUSE 100
LOW W2
PAUSE 100
NEXT

GOTO ini


Thanks, Mark

Paul Baker

You may only address 16 pins at a time (0-15 or 16-31), using the statement MAINIO to use the first bank and AUXIO to address the second. Refer to the stamp manual for the use of the two commands.

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·1+1=10

Jon Williams

Here's a subroutine to "virtualize" your pins so that you can set any one of them (0 - 31) to 0 (low) or 1 (high).

Setup_Pin:
· IOTERM thePin / 16················· · ' point to correct pin bank
· thePin = thePin // 16·············· · ' truncate 'bank' from pin
· DIRS.LOWBIT(thePin) = 1············ · ' make the pin an output
· OUTS.LOWBIT(thePin) =·pinLevel······· '·set the pin level
· RETURN

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Jon Williams
Applications Engineer, Parallax

allanlane5

If I'm not mistaken, if you're using 10 mA per LED, 21 LED's would be 210 mA. That's WAY more than the PIC chip inside the BS2p40 will drive.

You should probably add 2 ULN2008 darlington chips to the circuit to handle the current for you.

Now, if you're using "High efficiency" LED's, of 1 to 3 mA each, that's below the 50 mA limit for the PIC chip, and you'd be okay.

Chris Savage

In the original post the LEDs were being turned on, then off before the next one was turned on.· Following this concept he should be fine.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

allanlane5

Fair enough. I assumed the original post code was test code, and that there was some reason for having 21 LED's that he MIGHT want them all on at the same time at some point.

If not, then you're right, it's not a problem.

LoopyByteloose

Only the BS1 and BS2 use PIC chips.

That one is an SX-Ubicom, soon to be an SX-Parallax chip. It actually may handle a bit more power. [noparse][[/noparse]read the specifications]

Alternatively, he can use three shift registers and get 24 leds lit from one data pin, one clock pin, and one latch pin. There are even 'high power output shift registers' that can eliminate the UNL2308.

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"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

Chris Savage

Allan,

· He may not know that, so your post is justified in simply making him aware of this potential problem.· I was just going by the original code posted.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

Markus

Thanks,


I was testing the BSP40 with LEDs
Then it seems that Basic Stamp P40 couldn't turn on and off
more than 16 LEDs at the same time.
( Regarding Paul Baker reply )

Thanks for all the support. Mark

Jon Williams

Small scale microcontrollers an only sink/source so much current -- this is not a function of the BASIC Stamp, but the PIC or SX micro at its core. Similar 8-bit microcontrollers have similar limitations, and if you need to run a bunch of LEDs you have to control the current. You can either use very low current LEDs (usually not very bright) or put a buffer in between the microcontroller and the standard LED circuits you want to illuminate.

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Jon Williams
Applications Engineer, Parallax

allanlane5

Or, as seems true here, if you're just creating a 'test jig' and cycling each LED one at a time, you should be OK without a buffer.

Markus

Thanks Jon,

The current is not my problem.

The problem I have is to use the all the Basic Stamp P40 pins at a time,
something like:

' {$STAMP BS2p}
' {$PBASIC 2.5}

High 1
High 2
High 3
High 4
High 5
High 6
High 7
High 8
High 9
High 10
High 11
High 12
High 13
High 14
High 15
High 16
High 17
High 18
High 19
High 20
High 21

END

Please suppose the I/O consuption is not the problem because I
could use a very little led and the total comsumption of all pins at the
same time is 15 mA only. I that possible?


Thanks, Mark

Jon Williams

You cannot do anything past HIGH 15 -- this is just one of the rules of PBASIC.· The subroutine I wrote earlier in this thread will let you accomplish what you want, though the syntax would look something like:

Main:
· FOR thePin =·1 TO 21
··· pinLevel = 1············ ' make pin high
··· GOSUB Setup_Pin··········' do it
· NEXT

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Jon Williams
Applications Engineer, Parallax