I2C and Serial?

rory · Post by **rory** » Thu Jan 13, 2005 3:46 pm

I'm using a LK204-25. I'm able to talk to it over I2C and serial lines without any problems (having both cables plugged in all the time).

What I've found, though, is that since the I2C is connected, all the button presses get sent out over I2C, and not the serial line. Is there any way to get those button presses over the serial line?

Tom · Post by **Tom** » Fri Jan 14, 2005 10:10 am

Hi Rory,

Thank you for posting at the LCD forums.

When you press a key via I2C communication they keys are being sent to the internal key buffer. The key buffer is something common that is used when communicating via I2C or RS-232. The ways the key is read in I2C communications is the keys are polled from the key buffer. You can poll the keys in RS-232 communication or have them auto transmit from the key buffer. If you set autotransmitt on, you can read the keypresses on the RX line via RS-232.

For more information on I2C with Matrix Orbital units go to http://www.lcdforums.com/forums/viewtopic.php?t=910.

Try this and let me know if it works out for you.

Best Regards,

rory · Post by **rory** » Fri Jan 14, 2005 11:47 am

So keypresses are put into the internal key buffer, and then these can be retrieved via I2C or RS-232?

What we have seen here is that we can retrieve the keypresses over RS-232 without any problems, but as soon as we plug in an I2C cable (even if we're not sending or requesting any data over that bus), we don't see anything over the RS-232 line. Is that the expected behavior, or do you think we're doing something wrong?

Thanks!

Tom · Post by **Tom** » Fri Jan 14, 2005 1:45 pm

Correct, the keypresses are placed inside a buffer, and it is retrieved via I2c or RS-232.

Can you try turning auto transmitt off of the RS-232 line, and polling the keypad on the RS-232 line.

I do not see anything wrong with what your doing, unless you have wires connected improperly or it is a coding problem

Best Regards,