Hello,
I'm developing an application based on Spotspear's 1.44-inch keychain board.
The device is battery-powered, so deep sleep is required!
Everything works correctly, including the display addressing and the processor's deep sleep procedure.
However, I can't put the display really into sleep mode using the enableDisplay() method of the Arduino_ST7735 library.
It turns out that using this method is ineffective regarding the backlight. The screen goes blank, but the backlight stays on.
It should be noted that on this board, the display's BackLight is physically wired to 3.3V.
Should I note that this method doesn't affect the backlight?
Thanks in advance for your help...
Hello @sergio83100.
It seems the "new forum" has put code tags around your post. Please, edit your post and remove the two sets of three "ticks" ( ``` and ``` ) causing the text to be in a "code block."
Thanks xfpd, it is done …
Hi @sergio83100 ,
unfortunately your change does not appear on my screen ... Correctly formatted it should look like this
Post #1 without code tags:
Hello,
I'm developing an application based on Spotspear's 1.44-inch keychain board.
The device is battery-powered, so deep sleep is required!
Everything works correctly, including the display addressing and the processor's deep sleep procedure.
However, I can't put the display really into sleep mode using the "enableDisplay()" method of the Arduino_ST7735 library.
It turns out that using this method is ineffective regarding the backlight. The screen goes blank, but the backlight stays on.
It should be noted that on this board, the display's BackLight is physically wired to 3.3V.
Should I note that this method doesn't affect the backlight?
Thanks in advance for your help...
End of post #1
I found older posts with a similar topic, e.g.
https://forum.arduino.cc/t/1-8-tft-st7735-backlight-control/562804/14
and
https://github.com/Bodmer/TFT_eSPI/discussions/998
So it is a generally known issue ... if one searches for it ... 
The backlight has to be controlled separately ...
I guess you are using the Adafruit library? If yes, you might also check the function enableSleep() instead of enableDisplay():
Good luck!
ec2021
Since the backlight is hardwired to 3.3V, there is nothing you can do in code to turn it off. If you want to be able to turn it off, you will have to modify the wiring but cutting a trace and putting in transistor tied to one of your pins so you can turn it on/off.
Hi ec2021 and blh64,
Sorry for that but I missed a pair of double quote (!) now my thread should be correctly readable!
In deed generaly the backlight is not under the ship display controler control. Regarding the size of the board, it is almost impossible to cut a track an insert a transistor to control the backlight.
May be the board designer in Spotspear did not think enough of ergonomy?
Nevertheless thanks to both of you trying to help me!
Regards