WIO Terminal - Custom Module to turn off / on LCD Backlight

Products & Technology Wio Terminal
#1

I have created a module, (based on the WT_LCDBacklight module), and added 2 additional methods to allow turning off and on the LCD Backlight from Ardupy Micropython.

The code in the module is as follows:

#define LCD_BACKLIGHT (72Ul)

void common_hal_lcdbacklight_turn_off(abstract_module_t *self) // function to turn off the backlight
{
pinMode(LCD_BACKLIGHT, OUTPUT);
digitalWrite(LCD_BACKLIGHT, 0);
}

void common_hal_lcdbacklight_turn_on(abstract_module_t *self) // function to turn on the backlight
{
pinMode(LCD_BACKLIGHT, OUTPUT);
digitalWrite(LCD_BACKLIGHT, 1);
}

I then create and flash a build and I can see the methods but the digitalWrite doesn’t change the LCD_BACKLIGHT to 0 and therefore it never turns off the LCD Backlight.
I have added the following printf before and after the method and sure enough it is always 1:

printf("common_hal_lcdbacklight_turn_off BEFORE -> LCD_BACKLIGHT = %u, current = %d\n\n", LCD_BACKLIGHT, digitalRead(LCD_BACKLIGHT));
pinMode(LCD_BACKLIGHT, OUTPUT);
digitalWrite(LCD_BACKLIGHT, 0);    
delay(10);
printf("common_hal_lcdbacklight_turn_off AFTER -> LCD_BACKLIGHT = %u, current = %d\n\n", LCD_BACKLIGHT, digitalRead(LCD_BACKLIGHT));

Any ideas why the digitalWrite has no effect on the 72Ul pin?

#2

Hi @jim_macb,

Could you try this first with Arduino to check?

Best Regards,
Lakshantha

#3

Hi @lakshan, yes this works on Arduino and it is that code that I was attempting to use here.

#4

Hi @jim_macb,

First of all, you cannot use 72Ul, PinMode and digitalWrite on ArduPy, because they are not included in the ArduPy APIs.

You could check these documents for further clarification:


  • Define a pin:
p3 = Pin(3, Pin.OUT)    // Setting Pin 3 as an output pin
  • Set the pin to HIGH:
p3.on()
  • Set the pin to LOW:
p3.off()

I would suggest you to check out this playlist to learn more about ArduPy:

Even though 72Ul pin is defined for Arduino, you cannot directly use that pin with ArduPy because it is not defined within ArduPy APIs.

However, there is a way to achieve what you have been trying before. That is by using the following ArduPy library:

This is used to control the brightness of the LCD. But however, you can use it to turn the LCD ON and OFF as well by using the following codes.

  • Turn OFF LCD:
backlight.setBrightness(0)
  • Turn ON LCD:
backlight.setBrightness(100)

Here is an example sketch for your reference. This would turn ON/OFF LCD every 2 seconds.

# include libraries  
from arduino import wt_lcdbacklight
from machine import LCD
import time

lcd = LCD() # initialize LCD
backlight = wt_lcdbacklight() # initialize backlight

def main(): # main function 
    lcd.fillScreen(lcd.color.RED) # fill background 

    while True: # while loop
        backlight.setBrightness(0) # turn off the LCD backlight
        time.sleep(2) # delay for 2 seconds
        backlight.setBrightness(100) # turn on the LCD backlight
        time.sleep(2)

if __name__ == "__main__": # check whether this is run from main.py
    main() # execute function

Please try the above methods and share your updates.

Hope it helps.

Best Regards,
Lakshantha

#5

Hi Lakshantha,
We currently use a slightly modified WTbacklight module that I have modified to simply be “turnOff” and “turnOn” functions setting as you say, the backlight to 0 or 100 accordingly.

I originally in this C library tried to manipulate 72Ul because of the reason you say that Ardupy hardware ID’s only go up to 64 but as I say, although it accepted the call it had no effect from out c module.

Anyway, I will leave the code as adjusting the backlight to 0 or 100 until Ardupy catches up and exposes 72Ul as an allowable hardware id or the Ardupy LCD class exposes a working “Turn Off” and “Turn On” method which would be useful.

Thanks for your support.

1 Like