interfacing LCD panel to BBB

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1

we are trying to interface some cheap LCD panel to the BBB
after checking some OpenSource designs we noted that all of them dont connect the data and control line from the beagle directly to the LCD .
some designs are adding serial resistors on each line like this one , page #7
http://www.4dsystems.com.au/new/productpages/4DCAPE-43/downloads/4DCAPE-43(T)_datasheet_R_1_4.pdf

or even more adding a transceiver IC that is not inverting or level-shifting the signals like the LCD capes made by circuitco , page #21
http://www.openhacks.com/uploadsproductos/beaglebone-lcd7-reva2-srm.pdf

so please , can any one explain those designs to me and how to calculate those resistors if they depend on some panel parameters
i have already modefied a DTO and loaded it and successfully fried a LCD panel that was directly interfaced to the beaglebonebBack

thanks in advance

2

we are trying to interface some cheap LCD panel to the BBB
after checking some OpenSource designs we noted that all of them dont connect the data and control line from the beagle directly to the LCD .
some designs are adding serial resistors on each line like this one , page #7
http://www.4dsystems.com.au/new/productpages/4DCAPE-43/downloads/4DCAPE-43(T)_datasheet_R_1_4.pdf

or even more adding a transceiver IC that is not inverting or level-shifting the signals like the LCD capes made by circuitco , page #21
http://www.openhacks.com/uploadsproductos/beaglebone-lcd7-reva2-srm.pdf

so please , can any one explain those designs to me and how to calculate those resistors if they depend on some panel parameters
i have already modefied a DTO and loaded it and successfully fried a LCD panel that was directly interfaced to the beaglebonebBack

The resistors are for impedance matching and to prevent reflections on long signal lines. These resistors have nothing to do with the make of the LCD, but are just standard practice when connecting high speed signal lines that are more than a few inches long. The resistors are used to slow down the signal transition and this eliminates refections on the signal lines. After you build the board, use an high speed oscilloscope to measure the signal quality. If you observe overshoot, then increase the resistor value. If the transitions are rounded, then decrease the resistor values.

Regards,
John