diff --git a/frequency.c b/frequency.c
index cf04b93..705b7a5 100644
--- a/frequency.c
+++ b/frequency.c
@@ -9,9 +9,43 @@
 #include "driverlib/interrupt.h"
 #include "inc/hw_types.h"
 #include "inc/hw_memmap.h"
+#include "driverlib/fpu.h"
+#include <math.h>
+#include "driverlib/pwm.h"
 
 #include "frequency.h"
 
+// start a pwm test signal
+void start_signal() {
+  // configure M0PWM2, at GPIO PF2, BoosterPack 1 header C1 pin 2
+  SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
+  GPIOPinTypePWM(GPIO_PORTF_BASE, GPIO_PIN_2 | GPIO_PIN_3);
+  GPIOPinConfigure(GPIO_PF2_M0PWM2);
+  GPIOPinConfigure(GPIO_PF3_M0PWM3);
+  GPIOPadConfigSet(GPIO_PORTF_BASE, GPIO_PIN_2 | GPIO_PIN_3, GPIO_STRENGTH_2MA,
+                   GPIO_PIN_TYPE_STD);
+  // configure the PWM0 peripheral, gen 1, outputs 2 and 3
+  SysCtlPeripheralEnable(SYSCTL_PERIPH_PWM0);
+  // use system clock without division
+  PWMClockSet(PWM0_BASE, PWM_SYSCLK_DIV_1);
+  PWMGenConfigure(PWM0_BASE, PWM_GEN_1,
+                  PWM_GEN_MODE_DOWN | PWM_GEN_MODE_NO_SYNC);
+  gPWMPeriod = roundf((float)gSystemClock / PWM_FREQUENCY);
+  set_pwm_period(gPWMPeriod);
+  PWMOutputState(PWM0_BASE, PWM_OUT_2_BIT | PWM_OUT_3_BIT, true);
+  PWMGenEnable(PWM0_BASE, PWM_GEN_1);
+}
+
+void set_pwm_period(uint32_t period) {
+    PWMGenPeriodSet(PWM0_BASE, PWM_GEN_1,
+                    gPWMPeriod);
+    PWMPulseWidthSet(PWM0_BASE, PWM_OUT_2,
+                     roundf((float)gPWMPeriod * 0.4f));
+    PWMPulseWidthSet(PWM0_BASE, PWM_OUT_3,
+                     roundf((float)gPWMPeriod * 0.4f));
+}
+
+
 
 void start_frequency_scan() {
     // config GPIO PD0 as timer input T0CCP0 at BoosterPack Connector #1 pin 14
diff --git a/frequency.h b/frequency.h
index 2698a7c..6e87bad 100644
--- a/frequency.h
+++ b/frequency.h
@@ -1,6 +1,12 @@
 #ifndef FREQUENCY_C
 #define FREQUENCY_C
+#define gSystemClock 120000000 // [Hz] system clock frequency
+
+#define PWM_FREQUENCY 20000 // PWM frequency = 20 kHz
+
 void start_frequency_scan(void);
+void set_pwm_period(uint32_t period);
 
 uint32_t gPeriod;
+uint32_t gPWMPeriod;
 #endif
diff --git a/main.c b/main.c
index 1ad61d3..0c75318 100644
--- a/main.c
+++ b/main.c
@@ -35,9 +35,7 @@
 #include "kiss_fft.h"
 #include "_kiss_fft_guts.h"
 
-#define PWM_FREQUENCY 20000 // PWM frequency = 20 kHz
 
-uint32_t gSystemClock = 120000000; // [Hz] system clock frequency
 
 #define PI 3.14159265358979f
 
@@ -93,30 +91,7 @@ const float gVoltageScale[VOLTAGE_SCALES] = {
 
 int Trigger(bool rising);
 
-// start a pwm test signal
-void start_signal() {
-  // configure M0PWM2, at GPIO PF2, BoosterPack 1 header C1 pin 2
-  SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
-  GPIOPinTypePWM(GPIO_PORTF_BASE, GPIO_PIN_2 | GPIO_PIN_3);
-  GPIOPinConfigure(GPIO_PF2_M0PWM2);
-  GPIOPinConfigure(GPIO_PF3_M0PWM3);
-  GPIOPadConfigSet(GPIO_PORTF_BASE, GPIO_PIN_2 | GPIO_PIN_3, GPIO_STRENGTH_2MA,
-                   GPIO_PIN_TYPE_STD);
-  // configure the PWM0 peripheral, gen 1, outputs 2 and 3
-  SysCtlPeripheralEnable(SYSCTL_PERIPH_PWM0);
-  // use system clock without division
-  PWMClockSet(PWM0_BASE, PWM_SYSCLK_DIV_1);
-  PWMGenConfigure(PWM0_BASE, PWM_GEN_1,
-                  PWM_GEN_MODE_DOWN | PWM_GEN_MODE_NO_SYNC);
-  PWMGenPeriodSet(PWM0_BASE, PWM_GEN_1,
-                  roundf((float)gSystemClock / PWM_FREQUENCY));
-  PWMPulseWidthSet(PWM0_BASE, PWM_OUT_2,
-                   roundf((float)gSystemClock / PWM_FREQUENCY * 0.4f));
-  PWMPulseWidthSet(PWM0_BASE, PWM_OUT_3,
-                   roundf((float)gSystemClock / PWM_FREQUENCY * 0.4f));
-  PWMOutputState(PWM0_BASE, PWM_OUT_2_BIT | PWM_OUT_3_BIT, true);
-  PWMGenEnable(PWM0_BASE, PWM_GEN_1);
-}
+
 
 uint32_t cpu_load_count(void)
 {
@@ -274,6 +249,12 @@ void handle_user_input() {
             case Down: // previous scale
                 local_options.voltage_scale = (local_options.voltage_scale + VOLTAGE_SCALES - 1) % VOLTAGE_SCALES;
                 break;
+            case SW1:
+                set_pwm_period(++gPWMPeriod);
+                break;
+            case SW2:
+                set_pwm_period(--gPWMPeriod);
+                break;
         }
 
         Semaphore_pend(options_sem, BIOS_WAIT_FOREVER);
@@ -320,11 +301,14 @@ void display_waveform(UArg arg1, UArg arg2)
         GrContextForegroundSet(&sContext, ClrWheat);
 
         snprintf(str, sizeof(str), "CPU Load %.1f%%", usage_percent);
-        GrStringDraw(&sContext, str, /*length*/ -1, /*x*/ 0, /*y*/ HEIGHT - 20, /*opaque*/ false);
+        GrStringDraw(&sContext, str, /*length*/ -1, /*x*/ 0, /*y*/ HEIGHT - 30, /*opaque*/ false);
 
-        float frequency = (float) gSystemClock / (float) gPeriod;
+        uint32_t period = gPeriod;
+        float frequency = (float) gSystemClock / (float) period;
         snprintf(str, sizeof(str), "f = %.1fhz", frequency);
         GrStringDraw(&sContext, str, /*length*/ -1, /*x*/ 0, /*y*/ HEIGHT - 10, /*opaque*/ false);
+        snprintf(str, sizeof(str), "T = %dc", period);
+        GrStringDraw(&sContext, str, /*length*/ -1, /*x*/ 0, /*y*/ HEIGHT - 20, /*opaque*/ false);
 
 
         if (local_options.fft) {