Matrix Orbital Corp

Last week I received my new GTT480272A.
I plan to use it with a PIC microcontroller, my question is:

What is easier to start with: 232TTL or I2C ?

Regards,

Klaus de Jong

Hello Klaus,

Unfortunately, as listed on our website, the GTT480272A does not yet support I2C protocol, so your choice will have to be TTL at this time. However, I would also say TTL is a much easier protocol with which to begin development. If you have any questions or concerns as you set up the hardware and start to develop code, please don't hesitate to post.

Thanks,
~Troy

Hello Troy,

OK, in general TTL will be more easy.

But when I understand things right TTL will need hardware handshaking. This is not supported by my PIC C compiler.

Can I use 232TTL with just Tx and Rx ?

Klaus

Hello Klaus,

You are correct, the GTT does require hardware handshaking; it cannot be turned off. However, we can work around it.

Hardware handshaking consists of two signals, request to send (RTS) and clear to send (CTS). If you turn off all handshaking on your controller, you can send data without any trouble; it will never send an RTS or wait for a CTS. However, when you read from the display, it will send out an RTS and wait for a CTS, if CTS is not received the display will hang; so reading will be troublesome, without modification.

If you are unable to supply RTS and CTS you can use a jumper to connect these two pins on the display. As soon as the dispaly sends a request it will receive a clear and data will be sent to the host without interruption.

Please note with these modifications flow control will essentially be off, so you will have to monitor the display and code to ensure buffers are not overrun and communication is successful.

~Troy

OK, thank you Troy,

This way I should be able get the touchscreen to work. For receiving data on my uC I normally use an interrupt, that should be no problem. And, if needed I can write code for handling RTS and CTS.

But now the soldered jumpers. I closed two jumpers for the I2C bus, I now must open them again, right?

Do I then have to close the four jumpers for the 232TTL ??

Regards,

Klaus

from: GTT480272A Hardware Manual Revision 1.3

quote

Similarly, in order to change the display to TTL mode, simply remove the zero ohm resistors from the RS232 or I

No worries Klaus,

I'm glad you can handle the TTL data without handshaking, but may add it later if needed. You are correct, to put the unit in TTL mode remove all other jumpers, and connect only the 4 pads labeled TTL with either one of the zero ohm resistors provided or a solder bridge.

~Troy

Thanx for your help.

I swapped the jumpers and now the display is showing strings, it accepts commands and it 'beeps'.

Regards,

Klaus

Thanx for your help.

I swapped the jumpers and now the display is showing strings, it accepts commands and it 'beeps'.

Regards,

Klaus

No worries Klaus, great to hear you are up and running. If you do have any further questions as you continue development, please don't hesitate to ask.

Thanks,
~Troy