diff --git a/main.c b/main.c
index 4297527..33b38c7 100644
--- a/main.c
+++ b/main.c
@@ -59,12 +59,14 @@ static kiss_fft_cpx in[FFT_BUF_LEN], out[FFT_BUF_LEN];
 
 typedef struct
 {
+    bool fft;
     uint8_t voltage_scale;
     uint8_t time_scale;
     uint8_t trigger_mode;
 } Options;
 
 Options options = {
+   .fft = false, // oscilloscope mode
    .voltage_scale = 4, // 2v
    .time_scale = 5, // 20us
    .trigger_mode = 1, // rising
@@ -185,7 +187,7 @@ void capture_waveform(UArg arg1, UArg arg2)
         int32_t adc_current_index;
         int32_t i;
 
-        if (true) {
+        if (options.fft) {
             adc_current_index = gADCBufferIndex;
             int32_t j = 0;
             for(i=adc_current_index-FFT_BUF_LEN; i<adc_current_index; i++) {
@@ -228,7 +230,7 @@ void process_waveform(UArg arg1, UArg arg2) {
         #define MAX(a,b) (((a)>(b))?(a):(b))
         #define CONSTRAIN(x) MAX(MIN(HEIGHT - 1, x), 0)
 
-        if(true) { // fft
+        if(options.fft) { // fft
             for(i=0; i<FFT_BUF_LEN; i++) {
                 //in[i].r = sinf(20*PI*i/FFT_BUF_LEN);
                 in[i].r = (float) adc_buffer_fft_sample[i] * w[i];
@@ -272,6 +274,9 @@ void handle_user_input() {
             case S1: // toggle edge
                 local_options.trigger_mode = (local_options.trigger_mode + 1) % 3;
                 break;
+            case S2: // toggle fft
+                local_options.fft ^= 1;
+                break;
             case Up: // next scale
                 local_options.voltage_scale = (local_options.voltage_scale + 1) % VOLTAGE_SCALES;
                 break;