Mixing 5V and 3.3V problems

[camerart]

Hi,
I've been happily using BASIC of some sort since, learning it by osmosis, while my son had it on the TV (No monitors then)

The Oshonsoft simulator is brilliant, but lately (more advanced programs) it can have faults when compiling. After much dliberating, while wondering what the difference is between the pile of PICs I have on a pile of circuits, and Arduino, apart from marketing. There may be differences, but not enough for me to change.

I have now decided to to 'make the effort' to change to 'C' and MPLABX. Unless fairly son, I am talked out of it, for another system.
C.

 

[Wp100]

Everyones different, but when you look at the connectivety of the Arduino and the free libraries that are around anything else seems so limiting.

While you can get complex devices working within minutes with the Arduino , it does not mean you loose any programing skills as you still need to build those modules into a viable project.

What I cannot readily see, is your what extra your move from Basic to MS C will really give you over all the effort ?
If you see some of the other posts from this forums members, MplabX and C does have its own problems.

Nigel would probably admit to being a die hard Assembly fan, but think even he has also started to look at / use the Arduino - what say you Nigel ?

For a fiver and a few hours to try things out, think you will find it a worthwhile exercise , either way ...
Plenty of online tutorials to give you along.

**broken link removed**

 

[Nigel Goodwin]

Nigel would probably admit to being a die hard Assembly fan, but think even he has also started to look at / use the Arduino - what say you Nigel ?

I've got some Arduino's to play with, but not done much with them yet - I am however currently using C rather than assembler on new PIC projects, I've also moved to using the 24F series because of the extra speed and memory size, as C (particularly the free version) is so much more inefficient than assembler.

 

[camerart]

Hi,
I always seem to get things working with PICs, and have lots of them in previous circuits with software for many different applications, so I don't see the need to change to Arduino.

I chose MPLABX as it is modern and because it is backed by Microchip, I think any problems will be sorted out.

As for 'C' I've had much advice to switch to it, and as I don't know one end of it from the other it seems a reasonable choice.

If anyone has the perfect solution, where I can watch a simulator as the program steps/runs. then I may change my thoughts.

C.

 

[spec]

Back to mixing 5V and 3.3V logic systems. The various resistor and FET home made translators do not meet the interface specifications so while you may get away with using home made translators, they inevitably lead to problems and don't even think about using them for high speed digital interfaces.

The bidirectional 4050 chip is similarly problematic.

spec

 

[Nigel Goodwin]

Back to mixing %v and 3.3V logic systems. The various resistor and FET home made translators do not meet the interface specifications so while you may get away with using home made translators, they inevitably lead to problems and don't even think about using them for high speed digital interfaces.

That's rather a sweeping statement, and completely misleading

They don't 'inevitably lead to problems', for the vast majority of purposes they will be 100% perfect, and more than good enough.

 

[camerart]

That's rather a sweeping statement, and completely misleading

They don't 'inevitably lead to problems', for the vast majority of purposes they will be 100% perfect, and more than good enough.

Hi S and N,
Have you followed that I'm not using any translators/level matching, this is why I'm using both 3.3V components?
C

 

[spec]

That's rather a sweeping statement, and completely misleading

They don't 'inevitably lead to problems', for the vast majority of purposes they will be 100% perfect, and more than good enough.

You missed out quite a bit in your quotation Nigel. The main one being that the level translators do not meet the interface requirements. I also said that with a low speed interface you may get away with them.

Your statement that it is a sweeping statement and misleading is opinion stated as fact and is a sweeping statement in itself- please stick to technical matters and leave the sweeping statements out.

spec

 

[Nigel Goodwin]

You missed out quite a bit in your quotation Nigel. The main one being that the level translators do not meet the interface requirements.

I left it out because it wasn't relevant, not that I've any interest in reading through specifications trying to find some imaginary possible problem. Actually working is what matters to the majority of people.

I also said that with a low speed interface you may get away with them.

Your statement that it is a sweeping statement and misleading is opinion stated as fact and is a sweeping statement in itself- please stick to technical matters and leave the sweeping statements out.

Perhaps you should do the same, in the vast majority of cases such interfaces are 100% effective, and claiming 'low speed' is meaningless unless you give some figures - as they work perfectly at most microcontroller speeds it's not really a problem?.

 

[camerart]

Now now lads!

I appreciate all replies, even if they are sweeping, it all adds to the general knowledge.

C.

 

[spec]

Now now lads!

I appreciate all replies, even if they are sweeping, it all adds to the general knowledge.

C.

Exactly. It is up to the OP to decide what he wants to go with.

It is not necessary or even desirable for everyone to agree about a subject.

spec

 

[spec]

Back to mixing 5V and 3.3V logic systems. The various resistor and FET home made translators do not meet the interface specifications so while you may get away with using home made translators, they inevitably lead to problems and don't even think about using them for high speed digital interfaces.

The bidirectional 4050 chip is similarly problematic.

spec

Getting back to my point, here is an illustration of the kind of problems that some home made translators produce:

**broken link removed**

spec

 

[camerart]

Getting back to my point, here is an illustration of the kind of problems that some home made translators produce:

**broken link removed**

spec

Hi S,
Ok, thanks, but I'm not using translators.
C.

 

[spec]

Hi S,
Ok, thanks, but I'm not using translators.
C.

Hi Camerart,

Yes, I know, but the subject was brought up and I just thought you would like some information about translators in case you wanted to use them and had problems with high speed/long lines.

Apologies for cluttering your thread.

spec

 

[Nigel Goodwin]

Getting back to my point, here is an illustration of the kind of problems that some home made translators produce:

Interesting article, but presumably he deliberately choose much too high resistor values to make it look bad?. It's usual to use 1K resistors to feed 3.3V SPI displays from 5V processors, and this works fine with a 16F1827, but dies at higher speeds from a 24F chip (which is 3.3V anyway, and doesn't need the resistors - but I was reusing the 16F1827 board). The 24F goes up to 4MHz SPI, the 16F was a fair bit lower, as I was only running it at 4MHz - I'll have to check the actual speed.

It's a shame he didn't test the FET converters, to see how they perform - as they should greatly out perform a simple resistor - if I get time I'll have to do the tests myself.

 

[Wp100]

It's a shame he didn't test the FET converters, to see how they perform - as they should greatly out perform a simple resistor - if I get time I'll have to do the tests myself.

It would be good to have details of such a proven fet diy logic level converter using readily available parts from a well followed author like yourself.

Perhaps an extra chapter on your tutorial showing various such circuits and their application /limitations /advantages.

 

[granddad]

Hi C ...
Had a few voltage mixups in the past have usually got round it with a simple 74HCT04 ( or 14) as a 3v to 5v output , 3v3 PIC24Fs have some 5v tollerant inputs . G

 

[camerart]

Hi C ...
Had a few voltage mixups in the past have usually got round it with a simple 74HCT04 ( or 14) as a 3v to 5v output , 3v3 PIC24Fs have some 5v tollerant inputs . G

Hi G,
Ok, thanks. I am using 3.3v to 3.3v so not needed.
C.

 

[ericgibbs]

hi Gran,
I guess you use two 74hct04 inverters is series to keep the signal sense.?

I use the 74hc125 for level shifting.

Eric

 

[granddad]

Hi Eric, Yes if i can't invert the output , but with some gigerepokery get away with one gate. also it allows a hi R pull-up to hold the signal low ( not floating ) until the 'system' is up and running , i will check out the 125 . G