HK Backlight mod - on when switch is off

[dr3x]

I did the HK backlight mod after installing the SmartieParts board and now the backlight comes on when I put in the battery and turns off when I switch the TX on so it is backwards of what I expect.

Found this writeup which may be relevant:
Install Instructions

Starting with Rev 2.2, the backlight is designed to operate on by default to make it compatible with all firmware options. However, in doing this it makes some firmware versions work "backwards". Until a given firmware package has specific support for the Rev 2.2 board, you may have to program it to be "off" when you expect the light to be on, and vice versa. Some technical jargon to help firmware authors: The light is powered when the 9x outputs a low (zero volt) signal on PB7 (aka "pin 17") . A high (5v) signal turns the light off. Sending a PWM of varying duty cycle will dim the light from 0 to 100% (frequency of 400hz if frequency can be set independent of duty cycle).

The TX is flashed with the latest er9x firmware.

Is there a way to toggle PB7 / pin 17 via one of the hardware switches programmatically?

[Westy]

In the Radio setup menu 1/6, you can set any switch you want on the light ..... hope that helps

[Kilrah]

If the backlight is on when the power switch is off you likely have a wiring error...
What "Backlight mod" did you do? With an SP board you'd just connect the backlight wires to the SP board and that's it.

[jhsa]

If you are using er9x go to the main settings menu by pressing long the left key, then scroll down to "Backlight Invert" and turn it "ON". There's a version of the SP board where the backlight works inverted. That's the reason for this setting on the radio..

João

[gohsthb]

Start with the first problem, like Kilrah said, the backlight should not be on if the radio is off. Somehow there is a wiring error. I'm guessing you have the SP board where there is a jumper to the main board next to the LCD ribbon connector? Still just guessing but you might have to swap that connector on the SP board you plugged the jumper into. And take a picture of your setup, that will make helping much easier for us.
-Gohst

[Westy]

good point

also I have noticed the latest V r786 in hte setup menu 1/6 ... "Backlight invert"

great thinking you clever developers you!

[jhsa]

that's why the backlight invert exists.. because of the smartie parts board..

Companion also has a compile option "SP2.2" Which is "backlight Support"..

[dr3x]

In the Radio setup menu 1/6, you can set any switch you want on the light ..... hope that helps

Tried setting the Gear switch to the backlight both with and without the backlight inverted option checked, unfortunately that didn't work...

[dr3x]

If the backlight is on when the power switch is off you likely have a wiring error...
What "Backlight mod" did you do? With an SP board you'd just connect the backlight wires to the SP board and that's it.

Yes the mod was to add the HK backlight; it has a connector that goes between the SP board and the TX board.

[dr3x]

If you are using er9x go to the main settings menu by pressing long the left key, then scroll down to "Backlight Invert" and turn it "ON". There's a version of the SP board where the backlight works inverted. That's the reason for this setting on the radio..

João

Thanks - didn't know about that. Unfortunately it didn't work...

[dr3x]

Start with the first problem, like Kilrah said, the backlight should not be on if the radio is off. Somehow there is a wiring error. I'm guessing you have the SP board where there is a jumper to the main board next to the LCD ribbon connector? Still just guessing but you might have to swap that connector on the SP board you plugged the jumper into. And take a picture of your setup, that will make helping much easier for us.
-Gohst

Here is a picture of the setup, do you mean the jumper labeled with A K?

So the wiring harness that came with the HK backlight is the group of red wires with one black wire, plugged into the SP board; the other end connects to the bunch of white wires that were plugged into that socket.

[Kilrah]

This connection is to be used on the stock ratio only, without the SP board. With the SP board you should connect as per the instructions here, on the little 2-pin connector on the right of the SP board.

Step 4: The LED panel requires modification to work with our programmer board. Simply snip the thin black and red wires as close as possible to its small circuit board they are attached to, so that you are left with just the panel and the two wires as shown below (basically, you want the two wires to be as long as possible). In this picture, we've added a connector (not included) so that we can easily disconnect the panel later. You can do this too, or simply solder the wires to the programmer board. A page describing the different LED connection options is here. Note: As of Rev 2.3 we now include a connector with red and black wires attached. Simply splice the LED wires to these connector wires (matching up the colors) and you should be good to go! We've made the wires long enough that you can elect to solder them directly to the LED backlight panel itself, but we leave this somewhat more advanced exercise to the user's discretion.

[s_mack]

Exactly. While I mean this with humor... this is a case of RTM (Read the manual) The way you installed it is what you'd do if you want to use the backlight but DONT want to use our advanced controller circuitry. HK uses the simple, and exceedingly common, but really "incorrect" method of driving an LED... by using a current limiting resistor in series with the LED. LEDs are best driven with a constant current, and the circuitry on the SP board provides that. But its not compatible with their resistor in place. That's why it is necessary to remove their resistor from the equation and link the LED + and - wires directly to our board as per our instructions. Don't want to modify it? That's fine... do exactly what you did, but then its just on/off with the radio's switch.