diff --git a/evga-card.c b/evga-card.c
index 7af209a..1cecfe4 100644
--- a/evga-card.c
+++ b/evga-card.c
@@ -27,9 +27,7 @@ int find_evga_gpu_i2cs(struct card_info *infos, int max_gpus)
 	
 	/* make sure we can open the i2c device */
 	if(dir == NULL)
-	{
 		return -1;
-	}
 	
 	/* loop over all i2c devices */
 	while((ent = readdir(dir)) != NULL)
@@ -50,10 +48,10 @@ int find_evga_gpu_i2cs(struct card_info *infos, int max_gpus)
 		/* See if it's a matching device for a supported EVGA card */
 		for (int i = 0; i < (sizeof(evga_pci_ids) / sizeof(struct gpu_pci_info)); i++) {
 			
-			if (pci_vendor == evga_pci_ids[i].vendor_id &&
-			pci_device == evga_pci_ids[i].device_id &&
-			pci_subsystem_vendor == evga_pci_ids[i].subvendor_id && 
-			pci_subsystem_device == evga_pci_ids[i].subdevice_id) {
+			if (pci_vendor           == evga_pci_ids[i].vendor_id &&
+			    pci_device           == evga_pci_ids[i].device_id &&
+			    pci_subsystem_vendor == evga_pci_ids[i].subvendor_id && 
+			    pci_subsystem_device == evga_pci_ids[i].subdevice_id) {
 				
 				/* Matched all PCI IDs, check for good firmware read */
 				strcpy(dev_file, "/dev/");
diff --git a/evga-card.h b/evga-card.h
index ad2f635..164fd33 100644
--- a/evga-card.h
+++ b/evga-card.h
@@ -1,5 +1,3 @@
-#pragma once
-
 #define NVIDIA_VEN                                      0x10DE
 
 #define NVIDIA_RTX3060_DEV                              0x2503
diff --git a/evga-icx.c b/evga-icx.c
index 631d24e..dd5444a 100644
--- a/evga-icx.c
+++ b/evga-icx.c
@@ -10,27 +10,126 @@
 
 #define MAX_GPUS 16
 
+static const char helpstring[] = "Available options:\n"
+                                 "--gpu N      : Control only GPU N instead of all supported cards\n"
+								 "--fan SPEED  : Set all fans at once to SPEED (see below)\n"
+								 "--fanN SPEED : Set fan N (0-3) to SPEED\n"
+								 "    SPEED may be one of the following:\n"
+								 "      'auto' to return the fan to its default control mode\n"
+								 "      N to set the fan to that manual % speed\n"
+								 "      [+/-]N to set that fan to an RPM offset from the GPU-controlled speed\n"
+								 "--reset      : Reset all fans to their default mode\n"
+								 "--sensors    : Print sensor readings even if setting a fan speed \n";
+								 
+void print_gpu_info(int gpu_num, struct card_info gpus[]);
+
 int main (int argc, char **argv)
 {
 	struct card_info gpus[MAX_GPUS];
-	int num_gpus;
+	int gpu_count;
+	int print_info = 0;
+	int gpu_num = -1;    /* Card to control */
+	char *fan_speed[ICX3_MAX_FANS] = {NULL}; 
 	
-	num_gpus = find_evga_gpu_i2cs(gpus, MAX_GPUS);
+	/* Input parsing */
+	for (int i = 1; i < argc; i++){
+		if (strcmp(argv[i], "--gpu") == 0) {
+			i++;
+			if (i < argc) {
+				gpu_num = atoi(argv[i]);
+			} else {
+				printf(helpstring);
+				return -1;
+			}	
+		} else if (strcmp(argv[i], "--fan") == 0) {
+			i++;
+			if (i < argc) {
+				for (int j = 0; j < ICX3_MAX_FANS; j++)
+					fan_speed[j] = argv[i];
+			} else {
+				printf(helpstring);
+				return -1;
+			}	
+		} else if (strncmp(argv[i], "--fan", 5) == 0) {
+			int fan_num = atoi(argv[i]+5);
+			i++;
+			if (i < argc) {
+				if (fan_num <= ICX3_MAX_FANS)
+					fan_speed[fan_num] = argv[i];
+			} else {
+				printf(helpstring);
+				return -1;
+			}
+		} else if (strcmp(argv[i], "--reset") == 0) {
+			for (int j = 0; j < ICX3_MAX_FANS; j++)
+				fan_speed[j] = "auto";
+		} else if (strcmp(argv[i], "--sensors") == 0) {
+			print_info = 1;
+		} else {
+			printf(helpstring);
+			return 0;
+		}
+	}
 	
-	if (num_gpus == -1) {
+	if (print_info == 0) {
+		/* Check for no fan commands given, so display info by default */
+		print_info = 1;
+		for (int i = 0; i < ICX3_MAX_FANS; i++) {
+			if (fan_speed[i] != NULL)
+				print_info = 0;
+		}
+	}
+	
+	gpu_count = find_evga_gpu_i2cs(gpus, MAX_GPUS);
+	
+	if (gpu_count == -1) {
 		printf("Error scanning I2C devices\n");
 		return -1;
-	} else if (num_gpus == 0) {
+	} else if (gpu_count == 0) {
 		printf("No supported GPUs found.\nAre you root or do you have udev access to i2c devices?\nDo you need to run `modprobe i2c-dev`?\n");
 		return -1;
 	}
 	
-	for (int i = 0; i < num_gpus; i++){
-		printf("#%d: %s (%s) @ %s\n", i, gpus[i].card_name, gpus[i].i2c_dev_path, gpus[i].pci_id);
-		print_icx3_fans(gpus[i].i2c_dev_path);
-		print_icx3_temps(gpus[i].i2c_dev_path);
-		printf("\n");
+	if (gpu_num > gpu_count - 1) {
+		printf("Invalid GPU number specified (%d, max %d)\n", gpu_num, gpu_count - 1);
+		return -1;
+	}
+		
+	
+	/* execute fan commands */
+	if (gpu_num == -1) {
+		for (int i = 0; i < gpu_count; i++){
+			for (int j = 0; j < ICX3_MAX_FANS; j++) {
+				if (fan_speed[j] != NULL)
+					set_fan(j, fan_speed[j], gpus[i].i2c_dev_path);
+					/* printf("gpu %d fan %d : %s\n", i, j, fan_speed[j]); */
+			}
+		}
+	} else if (gpu_num <= gpu_count - 1) {
+		for (int j = 0; j < ICX3_MAX_FANS; j++) {
+			if (fan_speed[j] != NULL)
+				set_fan(gpu_num, fan_speed[j], gpus[gpu_num].i2c_dev_path);
+				/* printf("gpu %d fan %d : %s\n", gpu_num, j, fan_speed[j]);*/
+		}
+	}
+	
+	/* print sensor info */
+	if (print_info) {
+		if (gpu_num == -1) {
+			for (int i = 0; i < gpu_count; i++){
+				print_gpu_info(i, gpus);
+			}		
+		} else if (gpu_num <= gpu_count - 1) {
+			print_gpu_info(gpu_num, gpus);
+		}
 	}
 	
 }
+
+void print_gpu_info(int gpu_num, struct card_info gpus[]) {
+	printf("#%d: %s (%s) @ %s\n", gpu_num, gpus[gpu_num].card_name, gpus[gpu_num].i2c_dev_path, gpus[gpu_num].pci_id);
+	print_icx3_fans(gpus[gpu_num].i2c_dev_path);
+	print_icx3_temps(gpus[gpu_num].i2c_dev_path);
+	printf("\n");
+}
 	
diff --git a/icx3.c b/icx3.c
index 58732c6..7bda775 100644
--- a/icx3.c
+++ b/icx3.c
@@ -4,6 +4,8 @@
 #include <unistd.h>
 #include <fcntl.h>
 #include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
 
 #include "icx3.h"
 
@@ -14,15 +16,10 @@ enum icx3_product_id check_for_icx3(char *i2c_dev_path)
 	int fd, read_result;
 	struct icx3_info *temp_info;
 	
-	fd = open(i2c_dev_path, O_RDONLY);
-	if (!fd)
+	fd = open_i2c_dev(i2c_dev_path);
+	if (fd == -1)
 		return ICX3_PRODUCT_NONE;
 	
-	if (ioctl(fd, I2C_SLAVE, ICX3_I2C_ADDR) < 0) {
-		close(fd);
-		return ICX3_PRODUCT_NONE;
-	}
-	
 	read_result = i2c_smbus_read_i2c_block_data(fd, ICX3_REG_READINFORMATION, ICX3_READINFORMATION_SIZE, data);
 	close(fd);
 	if (read_result == ICX3_READINFORMATION_SIZE) {
@@ -42,7 +39,68 @@ void print_icx3_fans(char *i2c_dev_path)
 	struct icx3_fan_control *fan_status; 
 	
 	/* First thing is to check for the product ID to figure out how many fans we have */
-	int fans_avail[ICX3_MAX_FANS] = {0};
+	char fans_avail[ICX3_MAX_FANS] = {0};
+	get_available_fans(i2c_dev_path, fans_avail);
+	
+	fd = open_i2c_dev(i2c_dev_path);
+	if (fd == -1)
+		return;
+	
+	for (int i=0; i < ICX3_MAX_FANS; i++) {
+		if (!fans_avail[i])
+			continue;
+		
+		read_result = i2c_smbus_read_i2c_block_data(fd, ICX3_REG_FANCONTROL + i, ICX3_FANCONTROL_SIZE, data);
+		if (read_result != ICX3_FANCONTROL_SIZE) {
+			close(fd);
+			return;
+		}
+		fan_status = (struct icx3_fan_control*) &data;
+		printf("%s: %d RPM (%d/%d%%, %s)\n",
+			icx3_fan_names[i],
+			fan_status->rpm_status,
+			fan_status->duty_status,
+			fan_status->duty,
+			icx3_fan_mode_names[fan_status->fanmode]
+			);
+	}
+	
+	close(fd);
+}
+
+void print_icx3_temps(char *i2c_dev_path)
+{
+	char data[I2C_SMBUS_BLOCK_MAX] = {};
+	int fd, read_result;
+	struct icx3_temp_sensors *temp_sensors;
+	
+	fd = open_i2c_dev(i2c_dev_path);
+	if (fd == -1)
+		return;
+	
+	read_result = i2c_smbus_read_i2c_block_data(fd, ICX3_REG_TEMPSENSOR, ICX3_TEMPSENSOR_SIZE, data);
+	if (read_result != ICX3_TEMPSENSOR_SIZE) {
+		close(fd);
+		return;
+	}
+	temp_sensors = (struct icx3_temp_sensors*) &data;
+	
+	float cur_temp;
+	short cur_data;
+	
+	for (int i=0; i<ICX3_NUM_TEMP_SENSORS; i++) {
+		/* endian swap */
+		cur_data = (short)(temp_sensors->data[2*i+1] << 8) | (short)(temp_sensors->data[2*i]);
+		/* temp is reported in tenths of deg C */
+		cur_temp = (float)cur_data/10;
+		printf("%s: %.1f C\n",
+		icx3_temp_sensor_names[i],
+		cur_temp);
+	}
+}
+
+void get_available_fans(char *i2c_dev_path, char *fans_avail)
+{
 	int product_id = check_for_icx3(i2c_dev_path);
 	
 	/* From ICX3TotalFanCtrl.cs */
@@ -87,6 +145,7 @@ void print_icx3_fans(char *i2c_dev_path)
 		fans_avail[3] = 1;
 		break;
 	default:
+	/* default fans only */
 		fans_avail[0] = 1;
 		fans_avail[1] = 1;
 		break;
@@ -94,70 +153,103 @@ void print_icx3_fans(char *i2c_dev_path)
 	/* Not sure what this case is for */
 		break;
 	}
-	
-	fd = open(i2c_dev_path, O_RDONLY);
-	
-	/* Error silently here because we should have already checked we can read the i2c in check_for_icx3() */
-	if (!fd)
-		return;
-	if (ioctl(fd, I2C_SLAVE, ICX3_I2C_ADDR) < 0) {
-		close(fd);
-		return;
-	}
-	
-	for (int i=0; i < ICX3_MAX_FANS; i++) {
-		if (!fans_avail[i])
-			continue;
-		
-		read_result = i2c_smbus_read_i2c_block_data(fd, ICX3_REG_FANCONTROL + i, ICX3_FANCONTROL_SIZE, data);
-		if (read_result != ICX3_FANCONTROL_SIZE) {
-			close(fd);
-			return;
-		}
-		fan_status = (struct icx3_fan_control*) &data;
-		printf("%s: %d RPM (%d/%d%%, %s)\n",
-			icx3_fan_names[i],
-			fan_status->rpm_status,
-			fan_status->duty_status,
-			fan_status->duty,
-			icx3_fan_mode_names[fan_status->fanmode]
-			);
-	}
 }
 
-void print_icx3_temps(char *i2c_dev_path)
+int open_i2c_dev(char *i2c_dev_path)
 {
-	char data[I2C_SMBUS_BLOCK_MAX] = {};
-	int fd, read_result;
-	struct icx3_temp_sensors *temp_sensors;
-	
-	fd = open(i2c_dev_path, O_RDONLY);
+	int fd = open(i2c_dev_path, O_RDONLY);
 	
 	/* Error silently here because we should have already checked we can read the i2c in check_for_icx3() */
-	if (!fd)
-		return;
+	if (fd == -1)
+		return -1;
+	
 	if (ioctl(fd, I2C_SLAVE, ICX3_I2C_ADDR) < 0) {
 		close(fd);
+		return -1;
+	}
+	return fd;
+}
+
+void enable_write(int enable, char *i2c_dev_path)
+{
+	int fd = open_i2c_dev(i2c_dev_path);
+	if (fd == -1)
+		return;
+	
+	unsigned char *data;
+	if (enable)
+		data = icx3_write_enable;
+	else
+		data = icx3_write_disable;
+	/* Enable or disable write */
+    i2c_smbus_write_i2c_block_data(fd, ICX3_REG_ENABLEWRITE, ICX3_ENABLEWRITE_SIZE, data);
+	
+	/* Read back the result to verify */
+	unsigned char read_result[ICX3_ENABLEWRITE_SIZE];
+	int write_ok = 0;
+	i2c_smbus_read_i2c_block_data(fd, ICX3_REG_ENABLEWRITE, ICX3_ENABLEWRITE_SIZE, read_result);
+	if (enable)
+		write_ok = (read_result[1] == 0xFC);
+	else
+		write_ok = (read_result[1] == 0xFE);
+	
+	if (!write_ok)
+		printf("Unable to enable/disable write on %s\n", i2c_dev_path);
+
+}
+
+/* Sets a given fan on the GPU according to a string setting
+'auto' resets the fan to default (fans 1-2 go to GPU control, 3-4 to +0 RPM offset from GPU control)
+A number without a sign (e.g. 50) manually sets the fan to a given % duty cycle
+A number with a sign (e.g. +500) sets the fan to run at an RPM offset from GPU control */
+void set_fan(int fan, char *setting, char *i2c_dev_path)
+{
+	char fans_avail[ICX3_MAX_FANS] = {0};
+	
+	struct icx3_fan_control fan_control = {};
+	struct icx3_fan_control fan_readback = {};
+	char reg = ICX3_REG_FANCONTROL + fan;
+
+	int write_result;
+	
+	/* Check to make sure we're setting a valid fan */
+	get_available_fans(i2c_dev_path, fans_avail);
+	if (fans_avail[fan] == 0) {
+		printf("Fan %d does not exist on this card \n", fan);
 		return;
 	}
-	
-	read_result = i2c_smbus_read_i2c_block_data(fd, ICX3_REG_TEMPSENSOR, ICX3_TEMPSENSOR_SIZE, data);
-	if (read_result != ICX3_TEMPSENSOR_SIZE) {
-		close(fd);
+
+	int fp = open_i2c_dev(i2c_dev_path);
+	if (fp == -1)
 		return;
-	}
-	temp_sensors = (struct icx3_temp_sensors*) &data;
 	
-	float cur_temp;
-	short cur_data;
-	
-	for (int i=0; i<ICX3_NUM_TEMP_SENSORS; i++) {
-		/* endian swap */
-		cur_data = (short)(temp_sensors->data[2*i+1] << 8) | (short)(temp_sensors->data[2*i]);
-		/* temp is reported in tenths of deg C */
-		cur_temp = (float)cur_data/10;
-		printf("%s %.1f C\n",
-		icx3_temp_sensor_names[i],
-		cur_temp);
+	fan_control.length = ICX3_FANCONTROL_SIZE - 1;
+	if (strcmp(setting, "auto") == 0) {
+		/* auto setting */
+		fan_control.rpm_offset = 0;
+		if (fan <= 1) 
+			fan_control.fanmode = ICX3_FANMODE_GPU_CONTROL;
+		else
+			fan_control.fanmode = ICX3_FANMODE_GPU_RPM_OFFSET;
+	} else if (setting[0] == '+' || setting[0] == '-') {
+		/* RPM offset */
+		fan_control.fanmode = ICX3_FANMODE_GPU_RPM_OFFSET;
+		fan_control.rpm_offset = atoi(setting);
+	} else {
+		fan_control.fanmode = ICX3_FANMODE_RPM;
+		fan_control.duty = atoi(setting);
 	}
-}
\ No newline at end of file
+
+	enable_write(1, i2c_dev_path);
+	
+    i2c_smbus_write_i2c_block_data(fp, reg, ICX3_FANCONTROL_SIZE, (char *)&fan_control);
+
+	/* Read back data and verify we set the fan properly */
+    i2c_smbus_read_i2c_block_data(fp, reg, ICX3_FANCONTROL_SIZE, (char *)&fan_readback);
+	if (fan_readback.fanmode    != fan_control.fanmode ||
+		fan_readback.rpm_offset != fan_control.rpm_offset ||
+		fan_readback.duty       != fan_control.duty)
+		printf("Error setting fan %d on %s\n", fan, i2c_dev_path);
+	close(fp);
+}
+
diff --git a/icx3.h b/icx3.h
index dd566d8..030beaf 100644
--- a/icx3.h
+++ b/icx3.h
@@ -1,18 +1,21 @@
-#pragma once
-
 #define ICX3_I2C_ADDR 0x2D
 
 #define ICX3_REG_FANCONTROL 80
 #define ICX3_REG_TEMPSENSOR 102
 #define ICX3_REG_READINFORMATION 177
+#define ICX3_REG_ENABLEWRITE 178
 
 #define ICX3_FANCONTROL_SIZE 0x09
 #define ICX3_TEMPSENSOR_SIZE 0x13
 #define ICX3_READINFORMATION_SIZE 0x06
+#define ICX3_ENABLEWRITE_SIZE 0x05
 
 #define ICX3_MAX_FANS 4
 #define ICX3_NUM_TEMP_SENSORS 9
 
+#define ICX3_WRITE_ENABLED 0xFC
+#define ICX3_WRITE_DISABLED 0xFE
+
 struct icx3_fan_control {
 	unsigned char length;
 	unsigned char fanmode;
@@ -68,10 +71,22 @@ enum icx3_product_id {
 	ICX3_PRODUCT_NONE = 0
 };
 
+enum icx3_fan_mode {
+	ICX3_FANMODE_DEFAULT,
+	ICX3_FANMODE_GPU_CONTROL,
+	ICX3_FANMODE_RPM,
+	ICX3_FANMODE_GPU_RPM_OFFSET,
+	ICX3_FANMODE_MCU_CURVE,
+	ICX3_FANMODE_MODE3,
+};
+
+static unsigned char icx3_write_enable[ICX3_ENABLEWRITE_SIZE] = {ICX3_ENABLEWRITE_SIZE-1, 198, 235, 234, 21};
+static unsigned char icx3_write_disable[ICX3_ENABLEWRITE_SIZE] = {ICX3_ENABLEWRITE_SIZE-1, 144, 235, 203, 52};
+
 static char *icx3_fan_names[] = {
+	"Fan 0", 
 	"Fan 1", 
 	"Fan 2", 
-	"Fan 3", 
 	"Ext. fan"
 };
 
@@ -99,3 +114,7 @@ static char *icx3_temp_sensor_names[] = {
 enum icx3_product_id check_for_icx3(char *i2c_dev_path);
 void print_icx3_fans(char *i2c_dev_path);
 void print_icx3_temps(char *i2c_dev_path);
+void get_available_fans(char *i2c_dev_path, char *fans_avail);
+int open_i2c_dev(char *i2c_dev_path);
+void enable_write(int enable, char *i2c_dev_path);
+void set_fan(int fan, char *setting, char *i2c_dev_path);
\ No newline at end of file