diff --git a/main.c b/main.c
index fc22d5c..65796d3 100644
--- a/main.c
+++ b/main.c
@@ -1,3 +1,4 @@
+
 /*
  * ECE 3849 Lab2 starter project
  *
@@ -42,9 +43,18 @@ uint32_t cputime_unloaded;
 uint16_t adc_buffer_sample[LOCAL_BUF_LEN]; // copy of g adc buffer
 uint8_t adc_buffer_processed[LOCAL_BUF_LEN]; // copy of g adc buffer
 
-uint8_t voltage_scale = 4; // 2v
-uint8_t time_scale = 5; // 20us
-uint8_t trigger_mode = 1; // rising
+typedef struct
+{
+    uint8_t voltage_scale;
+    uint8_t time_scale;
+    uint8_t trigger_mode;
+} Options;
+
+Options options = {
+   .voltage_scale = 4, // 2v
+   .time_scale = 5, // 20us
+   .trigger_mode = 1, // rising
+};
 
 // assuming square lcd
 #define HEIGHT LCD_VERTICAL_MAX
@@ -53,7 +63,7 @@ uint8_t trigger_mode = 1; // rising
 
 #define VIN_RANGE 3.3 // volts
 #define ADC_BITS 12
-#define ADC_OFFSET 30
+#define ADC_OFFSET 100
 
 #define VOLTAGE_SCALES 5
 const char * const gVoltageScaleStr[VOLTAGE_SCALES] = {
@@ -162,6 +172,9 @@ void capture_waveform(UArg arg1, UArg arg2)
     while(true) {
         Semaphore_pend(capture_sem, BIOS_WAIT_FOREVER);
 
+        // single read of options is atomic
+        int32_t trigger_mode = options.trigger_mode;
+
         int32_t adc_current_index;
         int32_t j;
         int trigger;
@@ -184,7 +197,9 @@ void process_waveform(UArg arg1, UArg arg2) {
     while(true) {
         Semaphore_pend(process_sem, BIOS_WAIT_FOREVER);
 
-        float fVoltsPerDiv = gVoltageScale[voltage_scale];
+        // single read of global options is atomic
+
+        float fVoltsPerDiv = gVoltageScale[options.voltage_scale];
         float fScale = (VIN_RANGE * PIXELS_PER_DIV)/((1 << ADC_BITS) * fVoltsPerDiv);
 
         int j;
@@ -204,28 +219,33 @@ void process_waveform(UArg arg1, UArg arg2) {
 void handle_user_input() {
     // handle buttons
     Button button = (Button) 0;
+    Options local_options = options; // this is the only writer
     while (true) {
         Mailbox_pend(button_mailbox, &button, BIOS_WAIT_FOREVER);
 
         switch (button) {
             case S1: // toggle edge
-                trigger_mode = (trigger_mode + 1) % 3;
+                local_options.trigger_mode = (local_options.trigger_mode + 1) % 3;
                 break;
             case Up: // next scale
-                voltage_scale = (voltage_scale + 1) % VOLTAGE_SCALES;
+                local_options.voltage_scale = (local_options.voltage_scale + 1) % VOLTAGE_SCALES;
                 break;
             case Down: // previous scale
-                voltage_scale = (voltage_scale + VOLTAGE_SCALES - 1) % VOLTAGE_SCALES;
+                local_options.voltage_scale = (local_options.voltage_scale + VOLTAGE_SCALES - 1) % VOLTAGE_SCALES;
                 break;
             case Right: // next scale
-                time_scale = (time_scale + 1) % TIME_SCALES;
-                set_frequency(gTImeScale[time_scale]);
+                local_options.time_scale = (local_options.time_scale + 1) % TIME_SCALES;
+                set_frequency(gTImeScale[local_options.time_scale]);
                 break;
             case Left: // previous scale
-                time_scale = (time_scale + TIME_SCALES - 1) % TIME_SCALES;
-                set_frequency(gTImeScale[time_scale]);
+                local_options.time_scale = (local_options.time_scale + TIME_SCALES - 1) % TIME_SCALES;
+                set_frequency(gTImeScale[local_options.time_scale]);
                 break;
         }
+
+        Semaphore_pend(options_sem, BIOS_WAIT_FOREVER);
+        options = local_options;
+        Semaphore_post(options_sem);
     }
 }
 
@@ -237,6 +257,10 @@ void display_waveform(UArg arg1, UArg arg2)
     while(1) {
         Semaphore_pend(display_sem, BIOS_WAIT_FOREVER);
 
+        Semaphore_pend(options_sem, BIOS_WAIT_FOREVER);
+        Options local_options = options;
+        Semaphore_post(options_sem);
+
         // calculate cpu usage
         uint32_t cputime_loaded;
         cputime_loaded = cpu_load_count();
@@ -261,12 +285,12 @@ void display_waveform(UArg arg1, UArg arg2)
 
         // info
         GrContextForegroundSet(&sContext, ClrWheat);
-        GrStringDraw(&sContext, gVoltageScaleStr[voltage_scale], /*length*/ -1, /*x*/ 0, /*y*/ 0, /*opaque*/ false);
-        GrStringDraw(&sContext, gTimeScaleStr[time_scale], /*length*/ -1, /*x*/ 60, /*y*/ 0, /*opaque*/ false);
+        GrStringDraw(&sContext, gVoltageScaleStr[local_options.voltage_scale], /*length*/ -1, /*x*/ 0, /*y*/ 0, /*opaque*/ false);
+        GrStringDraw(&sContext, gTimeScaleStr[local_options.time_scale], /*length*/ -1, /*x*/ 60, /*y*/ 0, /*opaque*/ false);
         snprintf(str, sizeof(str), "CPU Load %.1f%%", usage_percent);
         GrStringDraw(&sContext, str, /*length*/ -1, /*x*/ 0, /*y*/ HEIGHT - 10, /*opaque*/ false);
 
-        switch (trigger_mode) {
+        switch (local_options.trigger_mode) {
             case 1:
                 GrStringDraw(&sContext, "^", /*length*/ -1, /*x*/ WIDTH - 10, /*y*/ 0, /*opaque*/ false);
                 break;
diff --git a/rtos.cfg b/rtos.cfg
index 6f06a7a..806f8ac 100644
--- a/rtos.cfg
+++ b/rtos.cfg
@@ -593,3 +593,7 @@ var task5Params = new Task.Params();
 task5Params.instance.name = "user_input";
 task5Params.priority = 6;
 Program.global.user_input = Task.create("&handle_user_input", task5Params);
+var semaphore4Params = new Semaphore.Params();
+semaphore4Params.instance.name = "options_sem";
+semaphore4Params.mode = Semaphore.Mode_BINARY;
+Program.global.options_sem = Semaphore.create(1, semaphore4Params);