[solved] Grove LCD RGB Backlight unknown I2C addresses

Hi there,

I got a GrovePi+ board and an LCD RGB Backlight. When I hook it up I notice two extra I2C addresses appear in i2cdetect result.

0x03 - unknown

0x62 - rgb

0x3e - characters

0x70 - unknown, and this one disappears sometimes

What are those two extra addresses? I really did quite a research and haven’t found an explicit answer yet.


Hi andras75,

Can you post here the results of the following procedures:

  1. use i2cdetect command with the GrovePi & with the LCD RGB

  2. use i2cdetect command with the GrovePi & without the LCD RGB

Also, please make sure you have plugged in the GrovePi on top of Rapberry properly - if you haven’t, then things might happen.

Also, you should make a firmware update to the GrovePi.
If you don’t have the Raspbian for Robots image, then I highly suggest using it asap.

After you’ve installed the Raspbian for Robots image, open up a terminal and follow this commands:

cd Desktop/GrovePi/Firmware
sudo bash firmware_update.sh

The last lines you get should look like this:

Here’s one advice I usually give: do everything meticulously and always follow the procedure - even if it sounds redundant at times - it will save you.

I have updated quite recently with the dexterindustries script, also the firmware is up-to-date.
I’m not complaining that it’s not working. :slight_smile: it’s perfectly working does what I want. But I would like to get some information about those extra I2C addresses.

Just point me to the right direction / datasheet! Thanks!

Hi andras75,

Thank you for your answer.

The RGB LCD has 2 chips with 2 different functionalities. One of it drives the LEDs and the other one drives the text that’s printed.

The text driver is one and only and has an address of 0x3e.

The LED driver has multiple addresses, of which we only need one. As it’s specified on page 8 (annex 7.1.1) in this datasheet (aka PCA9633), there are 3 fixed addresses for our 8-pin chip package (the PCA9633):

  1. address 0x70 - LED all call address - it’s on at startup and cannot be addressed individually

  2. address 0x03 - Software reset address - it’s on at startup and cannot be addressed individually

  3. address 0x62 - Slave address - it’s the one you are communicating with and is addressable

Hope everything is crystal clear now.

Thank you

Exactly what i needed.