Use IOCTL code to implement LCD backlight adjustment, and use ioctl code to implement LCD Backlight

Use IOCTL code to implement LCD backlight adjustment, and use ioctl code to implement LCD Backlight

Such Code cannot be found in China. Therefore, the following code is improved after the relevant code is referenced, and the implementation method uses IOCTL code to implement the LCD backlight adjustment function.

Suitable for tablets or laptops. It depends on BIOS support or not.

Compile the environment using the Dev-cpp tool.

#include <stdio.h>#include <stdlib.h>#include <windows.h>#include <ddk/Ntddvdeo.h>typedef struct _DISPLAY_BRIGHTNESS {    UCHAR ucDisplayPolicy;    UCHAR ucACBrightness;    UCHAR ucDCBrightness;} DISPLAY_BRIGHTNESS, *PDISPLAY_BRIGHTNESS;#define IOCTL_VIDEO_QUERY_SUPPORTED_BRIGHTNESS  CTL_CODE(FILE_DEVICE_VIDEO, 0x125, METHOD_BUFFERED, FILE_ANY_ACCESS)#define IOCTL_VIDEO_QUERY_DISPLAY_BRIGHTNESS CTL_CODE(FILE_DEVICE_VIDEO, 0x126, METHOD_BUFFERED, FILE_ANY_ACCESS)#define IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS CTL_CODE(FILE_DEVICE_VIDEO, 0x127, METHOD_BUFFERED, FILE_ANY_ACCESS)void help(void){fprintf(stderr, "(c) Tody, 2014\n");fprintf(stderr, "Usage: wbl.exe -b <level>\n");fprintf(stderr, "  Option:\n");fprintf(stderr, "     -b <level>\t brightness level need to be specified\n");fprintf(stderr, "\n  Error code:\n");fprintf(stderr, "     Pass: 0;  Fail: 1\n");exit(1);}int setBrightness(int level){HANDLE h ;DWORD nOutBufferSize = 256;BYTE SupportedBrightness[256];DWORD g_supportedLevelCount; DISPLAY_BRIGHTNESS DisplayBrightness;memset(SupportedBrightness, 0, sizeof(SupportedBrightness));/* use createfile function to open lcd.  * url from microsoft about IOCTL code.*  http://msdn.microsoft.com/en-us/library/windows/desktop/aa372703%28v=vs.85%29.aspx*/h = CreateFile("\\\\.\\LCD", GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, 0);if(h == INVALID_HANDLE_VALUE){printf("Open \\\\.\\LCD error");exit(1);}/* Query for display supported level */if(!DeviceIoControl(h, IOCTL_VIDEO_QUERY_SUPPORTED_BRIGHTNESS, NULL, 0, SupportedBrightness, nOutBufferSize, &g_supportedLevelCount, NULL)){printf("IOCTL_VIDEO_QUERY_SUPPORTED_BRIGHTNESS error - %d, - buffer: %d ", g_supportedLevelCount, nOutBufferSize);exit(1);}if (g_supportedLevelCount == 0)  /* 0 means not supported */{printf("\nLCD not support LEVEL COUNT", g_supportedLevelCount);exit(1);}DisplayBrightness.ucDisplayPolicy = 0;DisplayBrightness.ucACBrightness = level;DisplayBrightness.ucDCBrightness = level;/* Set display backlight level */nOutBufferSize = sizeof(DisplayBrightness);if(!DeviceIoControl(h, IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS, (DISPLAY_BRIGHTNESS *)&DisplayBrightness, nOutBufferSize, NULL, 0, &nOutBufferSize, NULL)){printf("IOCTL_VIDEO_SET_SUPPORTED_BRIGHTNESS error - %d, - buffer: %d ", g_supportedLevelCount, nOutBufferSize);exit(1);}Sleep(500); /* delay for some time while wmi event changed */nOutBufferSize = sizeof(DisplayBrightness);if(!DeviceIoControl(h, IOCTL_VIDEO_QUERY_DISPLAY_BRIGHTNESS, NULL, 0, (DISPLAY_BRIGHTNESS *)&DisplayBrightness, nOutBufferSize, &nOutBufferSize, NULL)){printf("IOCTL_VIDEO_QUERY_SUPPORTED_BRIGHTNESS error - %d, - buffer: %d ", g_supportedLevelCount, nOutBufferSize);exit(1);}printf("\nBrightness_AC: %d\nBrightness_DC: %d", DisplayBrightness.ucACBrightness, DisplayBrightness.ucDCBrightness);}int main(int argc, char *argv[]) {/* program with arguments support */if (argc == 3 && strcmp("-b", argv[1])==0){setBrightness(atoi(argv[2]));}else{help();}return 0;}

How to control the LCD12864 backlight, that is, how to use a single-chip microcomputer to adjust the brightness of the LCD12864 backlight, how to connect the hardware

The simplest is PWM. The backlight is controlled by a transistor, And the PWM inputs the baseline of the transistor.

How does XP Adjust the LCD backlight?

For a desktop, press the menu key on the monitor, find the brightness options, find the options to adjust the brightness, and then adjust the left and right arrows.