RTC SD2405 I2C and LCD1602 RGB conflict on I2C ?

[coltex]

Hello.

I have a strange phenomenon concerning I2C bus modules.

Modules: RTC SD2405 I2C and LCD1602 RGB

I'm trying to display text on an this LCD. It works fine until I use the RTC module. Then it starts endlessly displaying the last letter of the text.

(Everything from one company DFRobot , i belive it should work together)

The simplified code looks like this:

#include "GravityRtc.h"

#include "Wire.h"

#include "DFRobot_RGBLCD1602.h"

GravityRtc rtc; // Init RTC

DFRobot_RGBLCD1602 lcd(/*RGBAddr*/0x2D ,/*lcdCols*/16,/*lcdRows*/2); //16 characters and 2 lines of show


void setup() {

Serial.begin(9600);

rtc.setup();

lcd.init();

lcd.setRGB(111,254,244);

lcd.print("Texting");

}

void loop() {

rtc.read();

Serial.print(" Hour = "); // godzina

Serial.print(rtc.hour);

Serial.print(" Minute = "); // minuta

Serial.print(rtc.minute);

Serial.print(" Second = "); // sekunda

Serial.println(rtc.second);

}

Connections as in the picture:

Thank you for any help.

[Railroader]

There's no printing to the LCD in this code except for "Texting" in Setup.

[Koepel]

DFRobot LCD with RGB Backlight: https://www.dfrobot.com/product-1609.html
That is confusing, the display has a RGB_address and a I2C_address.
The RGB_address depends on the module:

       Moudule        | Version| RGBAddr|
-----------------------------------------
  LCD1602 Module      |  V1.0  | 0x60   |
  LCD1602 Module      |  V1.1  | 0x6B   |
  LCD1602 RGB Module  |  V1.0  | 0x60   |
  LCD1602 RGB Module  |  V2.0  | 0x2D   |

The I2C_address seems to be fixed to 0x3E: https://github.com/DFRobot/DFRobot_RGBLCD1602/blob/master/DFRobot_RGBLCD1602.h#L24

---

The DFRobot RTC module: https://wiki.dfrobot.com/Gravity__I2C_SD2405_RTC_Module_SKU__DFR0469
It's I2C address seems to be fixed to 0x32: https://github.com/DFRobot/Gravity-I2C-SD2405-RTC-Module/blob/master/GravityRtc/GravityRtc.h#L25

---

Things to do:

1. Please split the wires. The flat ribbon cable has 4 wires to each other. Split those wires please.
2. Run a I2C Scanner sketch with nothing connected, then with only the RTC connected, then with only the display connected, then with both.

[coltex]

Thank you for your willingness to help.

1. When I scan only RTC :
   I2C device found at address 0x32
   When I scan only LCD :
   I2C device found at address 0x2D
   I2C device found at address 0x3E

When I scan two I got 3 adresses.
I2C device found at address 0x2D
I2C device found at address 0x32
I2C device found at address 0x3E

So, LCD use 2 adresses ? maybe.

But , Now I see one more thing.
I I disconect modul of RTC , its the sam.
It looks like there is indeed a software problem.
it endlessly displaying the last letter of the text too.

Maybe problem in library from DTRobot ?

If I comment this line :
//rtc.read();
LCD start work properly. (RTC of course not.)

[TomGeorge]

Hi, @coltex
Welcome to the forum.

Have you tested the RTC on its own, with its own code?

Thanks.. Tom..

[coltex]

Hello,
I use libraries from DFRobot - vendor of LCD and RTC.

I just try with other library from DFRobot - "DFRobot_LCD.h" but the same efect.
Problem is in software, I can disconnect RTC - its the same.

Characters on display LCD appear in every cycle of this line :

rtc.read();

I have no idea why.

Besides this RTC work properly.

The RTC library interferes with the operation of the LCD module.