Prop Education kit Breadboard / using pins 29-31

Thomas Stickney

··· I am interested in adding an additional "permanent" circuit to the PEK breadboard
· by adding 8 switches and 8 LEDs to the right of the prop chip.
· using prop chip pins 24-31 as a 8-bit input switch port
·················and pins 16-23 as a 8-bit LED out port
····························· OR
······················pins 24-31 as a 8-bit LED out port
················and pins 16-23 as a 8-bit input switch port


··· My plan is to use the input pushbutton switch circuit and LED out circuit as used in the
· PEK lab·material.

··· Pins 0-7 and 8-15 are for add-on circuits.

··· What I am wondering is which circuit will provide the least conflicts to the Prop chip pins 28-29 which
··is used with 24LC256 EEPROM & pins 30-31 for the Prop Plug.

··· Thanks for any help.

Mike Green

You can't really use pins 28-31 for an input switch port without some buffering that's tri-stated during the Propeller's initialization and that would require a control pin to enable the buffer or a timer with a long enough timeout to accomodate any long download. You could use them as part of an 8-bit LED output port, but you'd want some kind of buffering so they don't load down the I/O pins. You'd have to be tolerant of some flashing while the Propeller goes through its boot code.

Fred Hawkins

Mike Green said...
You can't really use pins 28-31 for an input switch port without some buffering that's tri-stated during the Propeller's initialization and that would require a control pin to enable the buffer or a timer with a long enough timeout to accomodate any long download. You could use them as part of an 8-bit LED output port, but you'd want some kind of buffering so they don't load down the I/O pins. You'd have to be tolerant of some flashing while the Propeller goes through its boot code.

How about the kitchen light solution?

Oldbitcollector (Jeff)

Nice pic! Fred, what did you do that schematic in?

Oldbit

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Buttons . . . check. Dials . . . check. Switches . . . check. Little colored lights . . . check.

— Calvin, of 'Calvin and Hobbes.

deSilva

I think there is no need for a switch, when using active-low technique, pulling all lines up by 10k (you will even need only 3 resistors and also become complient to the I2C standard wrt clock line

Mike Green

Fred,
That would certainly work if he wants to do the switching manually.

deSilva,
It sounds like he wants to use DIP switches which would be set all the time, again not suitable without buffering.

deSilva

Right! I had a look at Fred's schematic only...

Fred Hawkins

Oldbitcollector said...
Nice pic! Fred, what did you do that schematic in?

Oldbit

An oldie but goodie-- MGI Photosuite 8.5.· Was bundled in a lot of win95 systems. One problem in XP, the paste from the print screen doesn't work directly; Control-v, Control-c in paint.exe first, then control-c to mgi.

You still can get a copy <$10 on ebay.· Be sure it isn't the later versions which modernized the interface into something worthless.

ps, most of the schematic was from the setup lab pdf.

Thomas Stickney

Thanks for the replies. I guess I will use LEDs on pins 24-31 with 470 ohm or 1000 ohm resistors instead of 100 ohm
as I had planned on.

deSilva

I do not use so many LEDs. Thus I do not need the 2 penny LEDs but pay 20 Cents for super bright. There is a astonishing development at the moment with "diffuse" LEDs illuminating not just a small angle...

What I want to say: With a raw power of 1.000 mcd you can easily reduce current to 1mA and the LEDs are still brighter than the garden variety! 1V/1mA = 1 k

Edit: Killed some typos..

Post Edited (deSilva) : 9/26/2007 10:55:40 PM GMT