I2C communication problems

ariclowe · Post by **ariclowe** » Wed Mar 25, 2009 5:44 pm

Hello,
Im new to the world of LCD's and I2C for that matter. Im attempting to communicate with an LCD model LK162-12 with a Freescale microcontroller via I2C and have had zero success. I moved the jumpers from 232 to I2C, set up the I2C comm. on my chip, set the baud rate to 93.75 kbps, and sent '254 /160 / 0' to turn off auto transmission of data in RS232. Following this Ive tried clearing the screen and writing various characters with no avail. Anyone have any suggestions? Any help would be greatly appreciated.

Thanks,

Aric

Raquel · Post by **Raquel** » Thu Mar 26, 2009 2:09 pm

Hi ariclowe,

Thank you for posting on the forum.

With I2C, the only hardware changes you need to do on the display side are the jumpers, as you have mentioned you have done (the third resistor from 232 can be discarded).

You will need to make sure that hardware connection on the master side is done properly as well (eg. pull up on SCL and SDA line).

On the firmware side, it is important to make sure that you are addressing the display properly. The default address for the display is 0x50. If you get the display's attention, it should ACK you at the 9th clock. Here's an assortment of I2C posts on the forum. Hopefully they help you out.

post 1 with scope capture
post 2 with scope capture
post 1 with code
post 2 with code

And as well, you might to check out our App Note I2C Section

I hope this helps.

Thanks and Best Regards,

NiTris · Post by **NiTris** » Thu Mar 26, 2009 4:20 pm

If you are new to i2c, double check that your i2c pins are all going the right direction (set as outputs), that your freescale is set as the i2c master, and that you have your SCL and SDA lines idle at the right state.