LK162-12 serial port LCD lockup

[Wayne Galaugher]

Ihave an lk162-12 attached to an 16f877 using the serial port. All is well sending code to the LCD using pin 3 and 5v through the rs232 for power to the LCD. I have not connected pin 2 to send data from the LCD during the early testing. I just started using pin 2 to test the keypad functions and found that as soon as I connected the pin to the PIC the backlight worked but nothing else. All the functions that worked before stopped and as soon as I take the pin off the PIC it starts working. I set the state of the port from the lcd LOW. Might I have to set the LCD to work on TTL voltage levels? I'm baffled.

[Raquel]

Hi Wayne,

Thank you for your post.

If you will be connecting the LK162-12 straight to the 16F877, then yes, you need to get the module to the TTL mode, which entails desoldering the RS232 connecttions, and soldering the TTL connections.

The unit worked before (receive only) because of a (probably) forgiving RS232 IC, which was happy to receive 0 and 5V. Connecting the transmit pin, though, mean the 16f877 received RS232 level voltages. The 16f877 will not like that.

Best Regards,

[Wayne Galaugher]

Thanks Raquel for your quick response. I thought that was the problem but could not find any documentation.

One thing that I did notice was very little code samples for Picbasic and how to get around the initial stages of talking to the LCD at 19,200. I've got some code that works very well with picss if think it would be of interest to others.

[Raquel]

Hello Wayne,
It'll be great if you will share your basic PIC code. If you please email tech support tlam@matrixorbital.ca, he can post your code in our application note section.
Thank you very much.