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Inverted backlight?


I wonder if somewhow my backlight colors are inverted

I could not find any description about the menu colors

In my case, the backlight when doing the self-test is blue

then when ready seems to be green+blue

Sleeping is red

and in menu all colors are OFF, I can bearly read the text with another light source

So are they inverted?

If so, I wonder if I can fix it by altering the line 506 in LiquidTWI2.cpp



  if (_backlightInverted) status ^= 0x7;




  if (!_backlightInverted) status ^= 0x7;



The colors should be:

State             Color             Backlight LEDs powered

Menu           WHITE           (Red + Green + Blue)

Self test        WHITE           (Red + Green + Blue)

Ready           GREEN           (Green)

Connected    YELLOW        (Red + Green)

Charging       BLUE             (Blue)

Error              RED               (Red)

Sleeping        PURPLE         (Red + Blue)

If you built your own hardware, you may have used a LCD that has a different LED pinout.

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well, to answer my own post:

!_backlightInverted  instead of _backlightInverted  does indeed invert the colors

I compiled it and now it's usable, although not as it should be.

Colors now are:

Ready: RED
Sleeping: BLUE+GREEN

The LCD pinout is the same, I did test the LCD using 5V, but the LCD colors are triggered with positive 5V, not with GND 0V

Maye the detected  LCD is wrong, is there any way to see what LCD type did openevse detect?

Or to force a specific LCD type?

It sounds like the pinout of Red and Green LEDs are swapped.

The pinout should be:

15 LED +

16 Red -

17 Green -

18 Blue -

OpenEVSE does not do any autodetection of LCD. You can set Monochrome or Color.


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the pinout should be the same, except for reversing of the GND and +5V, thus my need to invert the backlight

But indeed it would seem the red and green are swapped, thanks! I should have realized it too, but I did not see the pattern  :)

I will check the wiring between the LCD and MCP23017

If that data sheet cut you posted is accurate, you do not need to invert and all the colors should be correct.

Both the OpenEVSE standard display and your data are common Anode +5v on 15 and - GND for each color.

Notice the 3rd columd, it says: 5V for ON  and low lever (GND) for OFF  for pins 16-18.

And I can confirm that in practice I tested it and the RGB lights on with 5V on pins 16-18

Well, I did check my wiring and what do you know, indeed the Red and Green were inversed, just as you predicted  :)

So now colors look as they should, at least the ones I managed to test before connecting the cable going to the car and testing the charging / connected colors

anyway for future readers:  
if you have LCDs that have backlight colors triggered with 5V instead of GND,   adding just one character:  "!" and recompiling solves the problem  :)

And of course, having OpenEVSE Support telling you what should have been obvious helps a lot!

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