Matrix Keypad routine

[Ioannis]

Another transistor or other driver I suppose.

Microchip has such Mosfet drivers (either for high or los side)

Ioannis

[passion1]

Ioannis / Steve

I would like to drive a 220V circuit with a power mosfet.
Do you think an optocoupler is a MUST or will I be able to get away with a diode to protect my pic?
If so, what diode or alternative protection would you recommend?

[mister_e]

it's up to you. Everything will depend of what the whole beast will do, and how the enclosure design is done. But to me, as long as there's room to fit a transformer and optocoupler and keep away the AC line away of the user... i feel better and sleep all night without any problem.

What do you need to drive?

[Ioannis]

...

But to me, as long as there's room to fit a transformer and optocoupler and keep away the AC line away of the user... i feel better and sleep all night without any problem.

I double that. Even if the end user is well isolated from the circuit, YOU are not trying to make it work. You will have to debug the circuit while alive and sure put your life in danger.

How many pcs are you going to sell? If it is say low quantity, for sure you will be paid by your time to develop the system. That money should be more than enough to let you put that transformer without second thought.

In my country people say that coward's mother will never cry over the grave! Of course it sounds more elegant in greek than the awkard translation!!!

Ioannis

[passion1]

Ioannis / Steve

Thank you for the wise advice!! I agree 100%.

[bill12780]

Hello all,

I have to ask because I have NEVER seen it done any other way. But is it not just plain good design practice to current limit with series resistors and pull up or down ALL digital I/O's?

And as far as driving your 220AC device. You should ALWAYS use some sort of isolation device to protect your DC circuits AND the poor person that is trying to use them!

But back to the thread....

Tell me if I am missing something here and if this would work at all:

if doing a keypad scan could you not use portb 0-2 and portb 3-7 for a 3x4 keypad. then use a look up table to get the actual key pressed? If you could do this it would be easy to add "secret" key combinations to do special functions in the project.

I am just getting started here and learning lots by reading. I have spent quite some time looking over the Keypad code posted here and its VERY complex more so then I would have thought. am I missing something here?
(I am not saying anything bad about the code. I could just be ignorant to what it takes to actually do this. So please don't be insulted.)

Also, I see no accomidation in the keypad for compairing the input from the keypad to stored values for say "pin access" or the such. Or is this code ment to be only the keyscan?

Just asking?

;Smart A** Programing Joke starts here
cls
Print "Best Regards,"
Print "Bill12780"
end

[Darrel Taylor]

Hi Bill,

It's not that it really takes that much code to scan a keypad. You can write your own that's much simpler, (Except that YOU actually have to write it). And then it will probably only work with that one set of hardware that you wrote it for.

But mister_e's keypad module was written to work with Everybody's program. With lots of options to allow the user to customize it to work with whatever hardware they are using, and with different modes such as Auto Repeat, and Scan Once, or Modal modes. Without the user having to do much at all.

It looks complicated on the inside, but that's the part you don't need to worry about. All you have to deal with is the actual useage of the module. Which is really easy. Define your pins and desired features, use an @ READKEYPAD _KeyVar, and you're done.

It's just like when you use PicBasic Pro itself. You don't care how the code works inside the compiler. You just want to say LCDOUT "Hello World" and have it show up on the LCD display.

Also, I see no accomidation in the keypad for compairing the input from the keypad to stored values for say "pin access" or the such. Or is this code ment to be only the keyscan?

Correct. Just reads the keypad.
For some sample code that can recognize a sequence of key presses. This might help.

Combinaton Gate access
http://www.picbasic.co.uk/forum/showthread.php?t=5695

[RussMartin]

I have to ask because I have NEVER seen it done any other way. But is it not just plain good design practice to current limit with series resistors and pull up or down ALL digital I/O's?

This is what I was taught back in the "old days", but there are lots of circumstantial exceptions--there were circumstantial exceptions, then, too, but probably not as many of them!