Newhaven Display Forum

I too am having the same problem with a similar display (NHD-0420D3Z-NSW-BBW-V3).  Of the 8 displays I ordered, I can only change the black light on 3 of them.  On another 3, I can only change the backlight if the display powers up with the backlight already on.  I set the back light intensity every 500ms as part of a housekeeping loop.  Is there a way to hardwire the back light on continuously?  7 of the 8 will light the backlight in self test mode.  I am using I2C at 50khz.  All other commands seem to work fine.