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install 20x4 I2C Display - Problem without 3.3v ?

 

Hello to All!

I have a Ubitx project since a month or more and its time for ready to start receive..

Now i look for software, the KD8CEC - CEC v1.08 (or 1.097 when you say its better to use this), and my problem was to use the I2C Display 20x4 i have, because of i doesn't now which are the voltage options for optimal usage. When i was read about a few post of other user, i can't see the version of my Display! With this I2C was seen at all in forum post(the i2c display post) here it has a few capacitor and resistor at pcb which can see, but my don't have this !!!




and now i read it is harmful to use a connection to the pins on raduino which have the votage of the s5351, at 3.3v and the I2C LCD Display have 5v and this should be very bad. but on the picture i have post you can see that my version isn't same which i see on every post or site i searched for the topic - "ubitx I2C 20x4 Display" - and i read on W0EB I2C PDF that i should have a logic level converter 5v to 3.3v.... but i don't read anything on the KD8CEC homepage for any harm by this, installing the 20x4 I2C Display to the 4 pins at raduino..

so i read on and on and find the document of my Display an read this: "logiclevel 3.3v or 5v"... please look at datasheet here it says a few info about:

and here i have buy this (last year whitout use till today..) ? in english translated it was talk about a "Both 3.3V and 5V logic level (5V power supply) -> Sowohl 3,3 V als auch 5 V Logiklevel (Spannungsversorgung 5 V)
Features:
  • Modell: I2C LCD 20x4 Zeichen
  • HD44780 Industrie-Standard
  • Mit aufgel?teten I2C-Kommunikations-Adapter Dadurch werden nur 4 I/O Leitungen (Spannungsversorgung + 2xDatenleitungen) f¨¹r den Betrieb ben?tigt
  • Adapterchip: PCF8574AT
  • Sowohl 3,3 V als auch 5 V Logiklevel (Spannungsversorgung 5 V)
  • 20x4 Zeichen (4 Zeilen mit 20 Spalten)
  • Hintergrundbeleuchtung: Farbe Blau

Can somebody help me with this ? I don't have an idea if there was a integrated logic level converter or i have to buy or build the converter additional for use the I2C whitout any harm..

When i was look at the K8CEC website i see only the information for the pins that should be conect to but the I2C pcb on his LCD is on of that i have seen at all website i look and it have a few resistor and capacitor on it..that makes me confused, about my version and the information at datasheet and selling page that i have post now obove...

Its the last point then i want to test receive or i think about the desolder the I2C pcb from my LCD Display and connect it by the original pins which was the 16x2 display is connected.. is this an option to desolder the I2C panel from the display and conect it like i was thinkin or more things to do for this?(but that should be only an version of doing when the I2C version is not able)

Please help.

Regards Fabian
 

The issue is that I2C requires level conversion.

The direct use of 20x4 line without i2C does not require that as the display is 5V.
But that needs 4 data and 2 control lines (d4-D7,R,E)

Where the converter board for i2c is 3.3V for the I2C bus and requries 5V for the display.
I believe that board will accept the 3.3V I@C?from the controller and operates at
5V to suit the display.? ?Since I2C is used as a signal to the display that appears right.

>Sowohl 3,3V als auch 5V Logiklevel (@Spannungsversorgung 5V)
I believe that it accept either logic levels when powered with 5V.
My German is not so much.? But it would appear correct based on
a similar board I use for 20x2 line display.

The included document if from that vendor and shows hookup to a Uno and
only 5V power used. and the Uno signals are same as NANO as it is same
family MPU.

Allison

D810673B.PDF
D810673B.PDF

 

Here's an old post regarding the use of a 5v i2c LCD display with the Raduino:
? ??/g/BITX20/message/39966

Summary:
The two wire i2c bus is also used to talk to the 3.3v si5351, so we can't operate the i2c bus at 5v.
Most i2c devices such as an i2c LCD display will include pullup resistors to 5v, they should be removed.
The 3.3v pullup resistors R13 and R14 on the Raduino are sufficient.

There should be only one set of pullups on the i2c bus.
If you try to put 10 i2c devices (such as LCD displays) on an i2c bus and they all have
their own pullups, it won't work.? The open-collector drivers will see too much current.

ArduinoLand has been running on 5v for the last 20 years, most of the world has since
moved on to 3.3v or less.? So hooking up a newer part like the si5351 to an Arduino Nano
is a bit more complicated than it should be.

Jerry


On Fri, Sep 7, 2018 at 11:15 AM, ajparent1/KB1GMX wrote:
The issue is that I2C requires level conversion.

The direct use of 20x4 line without i2C does not require that as the display is 5V.
But that needs 4 data and 2 control lines (d4-D7,R,E)

Where the converter board for i2c is 3.3V for the I2C bus and requries 5V for the display.
I believe that board will accept the 3.3V I@C?from the controller and operates at
5V to suit the display.? ?Since I2C is used as a signal to the display that appears right.

>Sowohl 3,3V als auch 5V Logiklevel (@Spannungsversorgung 5V)
I believe that it accept either logic levels when powered with 5V.
My German is not so much.? But it would appear correct based on
a similar board I use for 20x2 line display.

The included document if from that vendor and shows hookup to a Uno and
only 5V power used. and the Uno signals are same as NANO as it is same
family MPU.

Allison

?

?
 

On Fri, Sep 7, 2018 at 11:15 AM, ajparent1/KB1GMX wrote:
The issue is that I2C requires level conversion.

The direct use of 20x4 line without i2C does not require that as the display is 5V.
But that needs 4 data and 2 control lines (d4-D7,R,E)

Where the converter board for i2c is 3.3V for the I2C bus and requries 5V for the display.
I believe that board will accept the 3.3V I@C?from the controller and operates at
5V to suit the display.? ?Since I2C is used as a signal to the display that appears right.

>Sowohl 3,3V als auch 5V Logiklevel (@Spannungsversorgung 5V)
I believe that it accept either logic levels when powered with 5V.
My German is not so much.? But it would appear correct based on
a similar board I use for 20x2 line display.

The included document if from that vendor and shows hookup to a Uno and
only 5V power used. and the Uno signals are same as NANO as it is same
family MPU.

Allison
Ok that means it doesn't work direct to the raduino conect like in picture on KD8CEC site here:
there is no word about anything of this problem with 3.3v and 5v.... please look at the site at the info below with the 20x4 I2C Display.. l this show only the connection to these pins and no other required like this line converter or a dissoldering from any 4.7k like i was read in a tutorial by W0EB, nothing ..nothing is there written..?? and on the picture a can't see any line converter, why he dont give any information?

ok other way i think of the option with desolder the I2C panel from my 20x4 I2C Display and put it on the original factory set 16x2 display pins.. this should work or not? it was an way to become a bigger display and till to the next time a have ordered the line converter, i have an running display .. should i dessolder now and put it in ?
 

On Fri, Sep 7, 2018 at 11:50 AM, Jerry Gaffke wrote:
Here's an old post regarding the use of a 5v i2c LCD display with the Raduino:
? ??/g/BITX20/message/39966

Summary:
The two wire i2c bus is also used to talk to the 3.3v si5351, so we can't operate the i2c bus at 5v.
Most i2c devices such as an i2c LCD display will include pullup resistors to 5v, they should be removed.
The 3.3v pullup resistors R13 and R14 on the Raduino are sufficient.

There should be only one set of pullups on the i2c bus.
If you try to put 10 i2c devices (such as LCD displays) on an i2c bus and they all have
their own pullups, it won't work.? The open-collector drivers will see too much current.

ArduinoLand has been running on 5v for the last 20 years, most of the world has since
moved on to 3.3v or less.? So hooking up a newer part like the si5351 to an Arduino Nano
is a bit more complicated than it should be.

Jerry


hey thanks too !

i have seen your post to late so i write now again..

when i was reading your post then i dont understand my I2C panel that's on my I2C Display in here. that is not the same i see at other pics by ubitx users they have showed.. and by the post pics above, you can see my I2C Display and there is nothing like an capacitor or resistor.. By the way i should ask "what ist an PULLUP Resistor?" i dont know this word, or is it the variable resistor that looks like a blue quadrat with a with plastic screw, to adjust the displays brightness, ..is that mean for pullup resistor? others not at my I2C panel and i dont know what you think about the KD8CEC website.. there would be a tutorial an there nothing was say about any 3.3v or desolder resistor.. that is making me crazy.. here ( l ) have you an idea for that website tutorial wasn't give information to the point of voltage on these pins using?

and what you say about my other idea, to desolder the I2C panel from Display and use it by put in the orignal display pins place? was that an option or there is an hiding problem too?

thanks
 

Fabian,

> By the way i should ask "what ist an PULLUP Resistor?"

Just a normal fixed resistor.

The i2c bus has two open collector signals named SDA (data) and SCL (clock).
Each of those two signals has a pullup resistor to 3.3v or 5.0v, with a value of perhaps 2k or 5k.
So when nothing is happening, both of those signals get pulled high.
But any device on the i2c bus can pull them low, then release the signal to allow it to go high again.

I am not familiar with your display, or with the i2c bus interface on your display.
I don't see any pullup resistors in the photo you showed.
They could be on the back of the i2c bus interface board.
Or they may not be present at all.
You could try measuring the resistance from the SDA and SCL pins to the upper power rail (with power off)
using an ohmmeter.
It is possible there are no pullup resistors at all on that board.

You might just try hooking up the SDA and SCL lines to the Raduino, see if it works.
The worst that will happen is that it will damage the si5351 chip on the Raduino,
but I doubt that will happen.

Getting i2c devices to work can be difficult.
Ii you need assistance you might be best off attending a local amateur radio club meeting,
see if someone there can help you get it going.

Jerry


On Fri, Sep 7, 2018 at 03:01 PM, sdr freak wrote:
when i was reading your post then i dont understand my I2C panel that's on my I2C Display in here. that is not the same i see at other pics by ubitx users they have showed.. and by the post pics above, you can see my I2C Display and there is nothing like an capacitor or resistor.. By the way i should ask "what ist an PULLUP Resistor?" i dont know this word, or is it the variable resistor that looks like a blue quadrat with a with plastic screw, to adjust the displays brightness, ..is that mean for pullup resistor? others not at my I2C panel and i dont know what you think about the KD8CEC website.. there would be a tutorial an there nothing was say about any 3.3v or desolder resistor.. that is making me crazy.. here ( l ) have you an idea for that website tutorial wasn't give information to the point of voltage on these pins using?

and what you say about my other idea, to desolder the I2C panel from Display and use it by put in the orignal display pins place? was that an option or there is an hiding problem too?

thanks
 

Hello Jerry!

Very much thanks and that is nice to hear these kind of post, i looking forward now and every post like this, which gives me good information is very nice!

ok when put the I2C board away from the display, with desoldering of this part, then i can post you few pics from the backside of the I2C board and i can run for first time my ubitx with the CEC software at the 20x04 Display in paralell-mode ? or is there a new problem to use it, when i desolder the I2C board awy from the Display and would run up like an normal paralell 20x04 Display? is there anything what i should or must do in progress of use as paralell Display, like other mods or something or is that ready to use at this point?
 

Fabian,

I am not familiar with your particular display or the CEC software.
Perhaps someone else can respond here after looking at the photo of your display
in your previous post, and tell you if it will work with the CEC software in parallel mode.
?
You should be able to determine if the pullup resistors for the SDA and SCL pins
are present by using an ohmmeter.? Measure from the SDA pin to the 5v power pin.
If the resistor is present, it will be between 5000 and 2000 ohms.? (If there is no resistor
present then that reading will likely be 50000 ohms or more.)? You can then find that resistor
so you can remove it by measuring from the SDA pin to the various possible resistors
and looking for zero ohms.? Then do the same for the SCL pin.

For the CEC software to be able to talk to the i2c adapter board, you must make sure
the software knows the correct i2c address to use as per post?/g/BITX20/message/39966
The easiest thing is to scan the i2c device by running special i2c scanning software on the Nano.

Also, the i2c adapter board must be using a particular interface IC that the CEC software
knows how to talk to.? I believe that should be either a?PCF8574T or?PCF8574AT

Jerry


On Mon, Sep 10, 2018 at 08:09 AM, sdr freak wrote:
Hello Jerry!

Very much thanks and that is nice to hear these kind of post, i looking forward now and every post like this, which gives me good information is very nice!

ok when put the I2C board away from the display, with desoldering of this part, then i can post you few pics from the backside of the I2C board and i can run for first time my ubitx with the CEC software at the 20x04 Display in paralell-mode ? or is there a new problem to use it, when i desolder the I2C board awy from the Display and would run up like an normal paralell 20x04 Display? is there anything what i should or must do in progress of use as paralell Display, like other mods or something or is that ready to use at this point?

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