reading a 4x4 switch matrix

[Pommie]

Hi Dan,

You may get some insight into peoples state of mind if you have a read of this thread.

Mike.
P.S. note that in post 112 I posted fully working code but it still continued for an additional 450 posts. This thread is a baby in comparison.

 

[Dan Soze]

You may get some insight into peoples state of mind if you have a read of this thread.

P.S. note that in post 112 I posted fully working code but it still continued for an additional 450 posts. This thread is a baby in comparison.

I can now appreciate where the relationship between the "experienced" forum members and MrDEB is presently at.

For my part I can tolerate thoughtless behavior from someone that is polite and well meaning. I am less accepting of intentionally rude behavior with cruel intent no matter the apparent justification or provocation.

It's obvious that MrDEB could be more explicit in acknowledgment to those that help him but then it does take an emotionally secure personality to truly be tankful to others.

In essence giving and gratitude are the social contract. To explicitly mandate them breaks the contract. For someone to recognize that the true reward of a gift given freely is that gratitude is a pleasant reward but not a mandatory response. Those with manners understand the social contract, those without seem never to learn.

 

[Pommie]

Even after 10 years of trying to help, I still try but occasionally get frustrated by the lack of progress.

Mike.

 

[Ian Rogers]

I think its like school.... When the teacher spends an hour talking to the students.... After the lesson he always asks "Everybody got that??" Then no one will dare reply.... It's when when you see someone is offering help and you are too embarrassed to acknowledge you don't quite get what's on offer!!

MrDeb still programs in a top to bottom approach... fetch the kettle, fill with water, press on button etc..

When offering solutions its better to "try" and keep to that approach.. C won't help and ASM won't help..

Mike's keyboard scan routine is brilliant.. but I'm afraid possibly at least 10 foot over the head..

 

[large_ghostman]

No worries mate, this ain't my first rodeo. I help where I can an do not expect much. My standards are so low that MrDEB should be hard pressed to disappoint me.

It seems to me that the group here is riding MrDEB a bit hard. As he is spending this evening playing Mexican Train dominoes at the community center for the +55 set perhaps he is someone rich in years. Such persons may enjoy the process of creation more than any individual completion.

The old adage that one can lead a mule to the lake but you can't make her drink applies.

Responses to this situation differ depending on your vocation, this is an end for an engineer but for a sales person other options could apply. So she doesn't drink but can she swim?

If it dont drink then burgers is the answer! Apparently we were eating them for years in the UK. .

Dan your first post made me smile, i remember taking similar stances 7 years ago........ This is my first Rodeo, mainly because these rodeos go on for a bit. Mexican Train is a quick interlude compared to a MD thread . You can tell everyone is getting older, this should be up to around page 15 by now! Guess were all slowing down lol.

That other thread Mike posted reminded me, anyone heard much from 3V lately? really miss having him post, i appreciate his situation but would be nice to know how he is getting on. Mike and 3VO were my two main teachers when i first started out, 3VO was brilliant at teaching and had so much patience with me. REALLY miss H being about.

And bill for that matter, not seen blueroom for a while! I still got a couple of his excellent Junebugs.

 

[granddad]

You can tell everyone is getting older

Age = experience ...

 

[JonSea]

...everyone is getting older....

Nope! I refuse!

 

[MrDEB]

There is a misconception here and I have repeated myself numerous times, I have followed most if not all suggestions posted. As an example, my present project the Domino counter calculator has the switch matrix and suggested basic code. And I did purchase the leaded solder suggested several months and and it works great, way better than the junk I was procuring from Radio Shack.
Yesterday after my last pos, I had some time and found where I crossed "shorted" the Vdd and grd.
The pic that burt posted in post#134 are my game hubs that I have revised since the switches are tooo expensive etc. The black ones are/ should be better. The pic has parts of suggested code from this forum.
I am wondering if maybe I am going too fast between projects and forum members get confused?? which project I am working on.
As for length or pages, sorry but detailed discussion makes a better mouse trap.

 

[Ian Rogers]

As for length or pages, sorry but detailed discussion makes a better mouse trap.

You mean "Jon trap"

 

[JonSea]

You mean "Jon trap"

I'm not sure whether I should laugh or cry! Probably just have my head examined....

 

[MrDEB]

No Jon your head is in good condition. I really enjoy your insight and suggestions.
As for the mouse trap, some things are better explained in length instead of a brief one or two sentences.
One of these days I plan to drive north and visit Seattle, been 10+ years and maybe we can meet for lunch or dinner and invent a better mouse trap if there is such a thing.

 

[JonSea]

Geez. I am thinking about MrDEB's projects while I'm in the shower!

I realized something. Somewhere along the line, we're changed projects and we're talking about 5 volt LCDs and therefore presumably not the POS 18F25K20 with its 3.3v limitation.

That means the diode in MrDEB's schematic isn't there for the voltage drop (to ensure battery voltage doesn't go too high) but for reverse polarity protection.

I suppose MrDEB plans on a Shotkey diode even though that's not what the schematic shows. I don't know what the intended power supply is for these "calculators" but most likely it's batteries and a 5 volt regulator. In any case for a battery powered circuit, a diode isn't the best reverse polarity protection because of the voltage drop and the power dissipation loss of the diode.

I have settled on using a P channel MOSFET for reverse polarity protection as described in my article Power Protection Circuits. With appropriate MOSFET selection, the voltage drop is less than that even of a Shotkey, and I×R losses are vanishingly small. On a surface-mount board, an SOT-23 package won't take up any more room than a diode.

If you want to use this idea for higher voltages, a zener diode and a resistor should be added to protect the gate from excessive voltage as mentioned in the commenrs to the article. For 5 volt supplies, only the MOSFET is required.

 

[JonSea]

There is some additional information here:

Power Protection Circuits - A Closer Look At The P Channel MOSFET

 

[MrDEB]

The diode is a simple 1n4148. It is there to drop the 4.5 volts from 3 AAA batteries to 3.4 aprox. This was somebody eles'es idea and it appears to work just fine. I have a circuit board with a K pic on it and the diode and everything seems to work just fine
Thanks for thinking about this. And yes I have a circuit board with provision for using the mosfet for battery reversed protection but after reading the data sheet for the battery holders I am using, it shows a reverse polarity protection already on the holder.
https://www.mouser.com/ds/2/209/EPD-200576-1171328.pdf

 

[JonSea]

Repeating once again, an LCD not explicitly supporting 3.3 volts isn't going to work unless you have a means of generating a negative voltage for Vo. Vo on a LCD designed for 5 volts is usually around 1 volt, so 4 volts less than the supply voltage. Operate it off 3.3 volts, and Vo will need to be about -0.7 volts.

 

[JonSea]

 

[MrDEB]

Am planning on using 5v pic and LCD
hopefully avoid voltage issues.
Trying to get the keypad16 working but so far no luck.
Have a 18f4321 wired up, lcd works as planned
have a test led that blinks as planned
just havn't got the keypad to display?
maybe an issue with cobbled keypad?
using keypad16.bas

 

[JonSea]

Just including the keypad file does absolutely nothing on its own as I explained in the two posts where I listed E X A C T L Y what you need to do.

If you expect any help, you need to post your code.

 

[JonSea]

From memory i am sure Nigel posted a pic of a pic and his thumb. I am sure he will correct me if i get it wrong... But i think he did something pretty bad to it and it got so hot his thumb was burnt, AFAIK the pic lived!! I think Nigel did as well lol, i am positive there is a post here on it. But 7 years a member and it gets harder to remember some the older posts.

That happens a lot with 79xx negative voltage regulators when you assume the pinout is the same as a 78xx. I had a TO220 imprint on my thumb for a long time.

 

[Dan Soze]

That happens a lot with 79xx negative voltage regulators when you assume the pinout is the same as a 78xx. I had a TO220 imprint on my thumb for a long time.

And remember that the hot end of the soldering iron is the wrong one to be holding. When you touch that end on more that 2 out of 5 times you're an engineer, 3 out of 5 times you're a firmware engineer, 4 out of 5 times you're a manager.