Okay, I still haven't gotten anything to display on the LCD.

Probing with a scope shows that the communication between the teensy and the module looks alright.

I even see voltages on some of the pins react proportional to the amount of pixels I'm allegedly writing to the screen. When the code was writing full black for a second and then full white for a second I could see the voltages on all the V lines go up or down with one second frequency. Changing the code to slowly ramp up and down the amount of pixels also shows gradually changing voltages.

I'm just not seeing anything on the display itself.

I also tried sweeping through the 0-255 range on the contrast register, and while this did show corresponding changes on the voltage pins, it did not show any change on the display itself.

Just to be sure I swapped out the LCD module for another and get the exact same result.

The datasheet page 32-34 seems to suggest that VLCD (pin 3 and 4) should be producing between 12 and 18 volts.

I'm seeing between 1.7 and 2.4 volts on those pins.

Unfortunately I'm running out of ideas on what could be going wrong. Does anyone have any suggestions?