diff --git a/DDCM1.m b/DDCM1.m
new file mode 100644
index 0000000..03e6658
--- /dev/null
+++ b/DDCM1.m
@@ -0,0 +1,123 @@
+//
+//  DDCM1.m
+//  NativeDisplayBrightness
+//
+//  Created by Cédric Vuillet on 05/08/2021.
+//  Copyright © 2021 Benno Krauss. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+#include "DDCM1.h"
+
+@import Darwin;
+@import Foundation;
+@import IOKit;
+
+// clang -fmodules -o i2cwrite i2cwrite.m && ./i2cwrite
+
+typedef CFTypeRef IOAVServiceRef;
+extern IOAVServiceRef IOAVServiceCreate(CFAllocatorRef allocator);
+extern IOAVServiceRef IOAVServiceCreateWithService(CFAllocatorRef allocator, io_service_t service);
+
+extern IOReturn IOAVServiceCopyEDID(IOAVServiceRef service, CFDataRef* x2);
+extern IOReturn IOAVServiceReadI2C(IOAVServiceRef service, uint32_t chipAddress, uint32_t offset, void* outputBuffer, uint32_t outputBufferSize);
+extern IOReturn IOAVServiceWriteI2C(IOAVServiceRef service, uint32_t chipAddress, uint32_t dataAddress, void* inputBuffer, uint32_t inputBufferSize);
+
+#define BRIGHTNESS 0x10
+#define CONTRAST 0x12
+#define AUDIO_SPEAKER_VOLUME 0x62
+#define AUDIO_MUTE 0x8D
+#define INPUT_SOURCE 0x60
+#define DPMS 0xD6
+
+struct DDCWriteCommand {
+    UInt8 control_id;
+    UInt8 new_value;
+};
+
+bool DDCM1Write(uint level) {
+    io_iterator_t iter;
+    io_service_t service = 0;
+    io_registry_entry_t root = IORegistryGetRootEntry(kIOMasterPortDefault);
+    kern_return_t kerr = IORegistryEntryCreateIterator(root, "IOService", kIORegistryIterateRecursively, &iter);
+    if (kerr != KERN_SUCCESS) {
+        IOObjectRelease(iter);
+        NSLog(@"Error on IORegistryEntryCreateIterator: %d", kerr);
+        return 1;
+    }
+
+    CFStringRef edidUUIDKey = CFStringCreateWithCString(kCFAllocatorDefault, "EDID UUID", kCFStringEncodingASCII);
+    CFStringRef locationKey = CFStringCreateWithCString(kCFAllocatorDefault, "Location", kCFStringEncodingASCII);
+    CFStringRef displayAttributesKey = CFStringCreateWithCString(kCFAllocatorDefault, "DisplayAttributes", kCFStringEncodingASCII);
+    CFStringRef externalAVServiceLocation = CFStringCreateWithCString(kCFAllocatorDefault, "External", kCFStringEncodingASCII);
+    
+    int found = 0;
+    while ((service = IOIteratorNext(iter)) != MACH_PORT_NULL) {
+        io_name_t name;
+        IORegistryEntryGetName(service, name);
+        if (strcmp(name, "AppleCLCD2") == 0) {
+            CFStringRef edidUUID = IORegistryEntrySearchCFProperty(service, kIOServicePlane, edidUUIDKey, kCFAllocatorDefault, kIORegistryIterateRecursively);
+            CFDictionaryRef displayAttrs = IORegistryEntrySearchCFProperty(service, kIOServicePlane, displayAttributesKey, kCFAllocatorDefault, kIORegistryIterateRecursively);
+            if (displayAttrs) {
+                NSDictionary* displayAttrsNS = (__bridge NSDictionary*)displayAttrs;
+                NSDictionary* productAttrs = [displayAttrsNS objectForKey:@"ProductAttributes"];
+                if (productAttrs) {
+                    NSString* monitorName = [productAttrs objectForKey:@"ProductName"];
+                    NSLog(@"Testing monitor %@ [UUID: %@]", monitorName, edidUUID);
+                    NSLog(@"Attributes: %@", productAttrs);
+                    found = 1;
+                }
+            }
+        }
+        if (strcmp(name, "DCPAVServiceProxy") == 0 && found == 1) {
+            IOAVServiceRef avService = IOAVServiceCreateWithService(kCFAllocatorDefault, service);
+            CFStringRef location = IORegistryEntrySearchCFProperty(service, kIOServicePlane, locationKey, kCFAllocatorDefault, kIORegistryIterateRecursively);
+            if (location == NULL) {
+                NSLog(@"No location for service %d: %s\n\n\n", service, name);
+                continue;
+            }
+
+            if (!avService) {
+                NSLog(@"No AVService for service %d: %s\n\n\n", service, name);
+                continue;
+            }
+
+            if (CFStringCompare(externalAVServiceLocation, location, 0) == 0) {
+                NSLog(@"Found External AVService for %d: %d", service, avService);
+            } else {
+                NSLog(@"Found Embedded AVService for %d: %d\n\n\n", service, avService);
+                continue;
+            }
+
+            struct DDCWriteCommand command;
+            command.control_id = BRIGHTNESS;
+
+            UInt8 data[256];
+            memset(data, 0, sizeof(data));
+            data[0] = 0x84;
+            data[1] = 0x03;
+            data[2] = command.control_id;
+            
+            command.new_value = level;
+            NSLog(@"Setting BRIGHTNESS to %d", command.new_value);
+
+            data[3] = (command.new_value) >> 8;
+            data[4] = command.new_value & 255;
+            data[5] = 0x6E ^ 0x51 ^ data[0] ^ data[1] ^ data[2] ^ data[3] ^ data[4];
+
+            for (int i = 0; i < 3; ++i) {
+                IOReturn err = IOAVServiceWriteI2C(avService, 0x37, 0x51, data, 6);
+                if (err) {
+                    NSLog(@"i2c error: %s", mach_error_string(err));
+                }
+                usleep(32000);
+            }
+        }
+    }
+    CFRelease(locationKey);
+    CFRelease(edidUUIDKey);
+    CFRelease(displayAttributesKey);
+    CFRelease(externalAVServiceLocation);
+    
+    return YES;
+}