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Forum Index : Microcontroller and PC projects : Help with SunFounder IIC I2C TWI Serial 2004 20x4 LCD Module Shield

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fapplin
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Joined: 14/02/2025
Location: United States
Posts: 3

Posted: 04:10pm 15 Feb 2025

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Hi.

I'm a retired programmer who plays a lot with small microcontrollers like Raspberry Pi Pico. I have programmed them with the Arduino IDE in C/C++ or used the Pico SDK in C. I just came across MMBASIC for the Pico a couple days ago and decided for fun to convert a working project that I used the Arduino IDE for and re-work in MMBASIC.

I have almost everything working but the 4 x 20 LCD panel (in 2 days). I found some old code that someone posted in 2014 that I'm using and it works, but it only works for 2 lines not 4.

https://www.thebackshed.com/forum/ViewTopic.php?FID=16&TID=6715

Does anyone have an idea of how to get the 3rd and 4th line working?

I promise to post the project when finished. The project lets a user choose a key and scale and it will light up an LED strip above a piano keyboard showing which keys are in that key and scale (scales are definable on an SD Card.

Thanks,

Frank

Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
Posts: 7585

Posted: 04:23pm 15 Feb 2025

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So, it's a display with the I2C module on it?

In that code look for the line:

SUB LCDI2C(LineNum,CharPos,Text$)

That's the call used to print to the display. So
LCDI2C(4,3,"Hello")
should (in theory) print "Hello" at the third position on the bottom line. I think.... :)

And welcome to the 'shed. :)

.
Edited 2025-02-16 02:24 by Mixtel90

Mick

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Preliminary MMBasic docs & my PCB designs

fapplin
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Joined: 14/02/2025
Location: United States
Posts: 3

Posted: 04:49pm 15 Feb 2025

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This is from his code:

SUB LCDI2C(LineNum,CharPos,Text$)
LOCAL I
IF LineNum=1 THEN I=(&H80 + CharPos-1) 'I=&H02
IF LineNum=2 THEN I=(&HC0 + CharPos-1)
LCDI2C_CMD(I)

FOR I=1 TO LEN(Text$)
LCDI2C_DATA(ASC(MID$(Text$,I,1)))
NEXT I

END SUB

So, he's only doing 2 lines. The hex values were going up by 64, so I tried:

IF LineNum=3 THEN I=(&H100 + CharPos-1)

It was just a guess, but it didn't work.

JohnS
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Joined: 18/11/2011
Location: United Kingdom
Posts: 4006

Posted: 04:52pm 15 Feb 2025

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hmm... looking at the code, SUB LCDI2C(LineNum,CharPos,Text$) checks LineNum against 1 and 2, setting I accordingly.

I expect it would need to check for 3 or 4 and set I (er, to &H40 and 0?)

I don't know the display needs, though.

John

JohnS
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Joined: 18/11/2011
Location: United Kingdom
Posts: 4006

Posted: 04:53pm 15 Feb 2025

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Oh, you beat me to it.

Bigger than &h40 does make sense - try a datasheet...

John

fapplin
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Joined: 14/02/2025
Location: United States
Posts: 3

Posted: 06:11pm 15 Feb 2025

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Through trial and error - this works!!

IF LineNum=1 THEN I=(&H80 + CharPos-1) 'I=&H02
IF LineNum=2 THEN I=(&HC0 + CharPos-1)
IF LineNum=3 THEN I=(&H94 + CharPos-1)
IF LineNum=4 THEN I=(&HD4 + CharPos-1)

Frank

lizby
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Joined: 17/05/2016
Location: United States
Posts: 3326

Posted: 06:22pm 15 Feb 2025

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Right. Typically (or at least frequently), the third line location is immediately following the first line (&H94-&H80 is 20 bytes further on), and the forth line immediately follows the second.

PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed

JohnS
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Joined: 18/11/2011
Location: United Kingdom
Posts: 4006

Posted: 01:48pm 16 Feb 2025

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Excellent!

John

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