LK202 with I2C bus

skisoo · Post by **skisoo** » Wed Apr 22, 2009 2:26 am

In my project, I want to use the matrix Orbital LCD LK202 with an ATmega128 through I2C.
I've tried a lot of things but nothing worked. (like sending messages to the LCD with the LCD adress and command codes)
My LCD works great on RS232.
How can I check if the I2C bus is working with my LCD ?

Thanks you for answers.

Raquel · Post by **Raquel** » Wed Apr 22, 2009 10:58 am

Hello skisoo,

Thank you for posting on the forum.

Here's some pointers on making I2C work on the LK202-25:
- make sure that the resistor jumpers are taken out from 232 and moved to I2C (only 2 are necessary for I2C)
- pull up resistors on SCL and SDA typically from 2k to 10k
- to start, keep the manual override on at power up, to assure that the address of the display is 0x50
- scope things out on SCL and SDA; we need to see that the display ACKs the I2C transactions

Check out this forum post. Hopefully it helps as well.

Thanks and Best Regards,

skisoo · Post by **skisoo** » Thu Apr 23, 2009 8:52 am

I have some questions.
I have 2 lcd lk202-25, one with chips in zone 1 (on the picture) and one whitout chips in this zone. What is the difference ?
What is the purpose of zone 2 (on the picture) ?

I've tried to monitor the I2C bus with an oscilloscope, I can clearly see the SCL on it but when I plug the LCD, I get nothing on the oscilloscope. (If I turn on the lcd first, I get the same thing).

Raquel · Post by **Raquel** » Thu Apr 23, 2009 11:29 am

Hi,

The component that lives in '1' is the regulator. If this component is populated, the display takes 9V to 15V input power. If it not populated, the display takes in 5V for power.

The 2 pads in '2' are spare pads for I2C pull up resistors. Most of the time, these pull up resistors live in the I2C master board, but they are here as complimentary pads, in case you do not have a I2C master board yet, ie. if you do not have a PCB yet, extra pads like these are handy.

Also, I want to add, in the picture, it does not look like you have completely taken the jumps in 232.

And, one most important thing to note: you have an old PCB revision. We have revised the LK202-25 PCB about 3 years ago. If you are developing, I suggest you get the newest PCB rev.

Thanks,