632 Serial Display problems


New member
I have a V1.2 Serial 632 display. Model number is SKD162-632SG-LG. Using the crystal control software I can display various information on the display. However when I connect the data in line from the seven pin solder pad to the TX line of my MCU the display does not respond. I understand that the MCU puts out inverted data and I have closed Jumper B. I have connected +5 to Vdd, ground to Vss and left Led+ unconnected. No cigar.

Here is the kicker when I applied +5 to Led+ all my commands coming in through data in (0-5v) were understood by the display and I was able to write characters and such. However when I reduce the backlight brightness by sending command 14 the display returns to the previous state of not responding to my commands. I understand that the backlight is PWM driven and that there may be noise but I shouldn't have this problem when the backlight isn't powered at all.

What am I missing? I don't want to use the backlight since it draws excessive power for an embedded application yet I don't want to use an RS232 driver IC since the 632 is advertised to accept 0-5v signals on the data in line.
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Try closing JPE on the module, as that sets the logic levels to 0-5v. Just connecting to pin 4 does not change the levels.