diff --git a/include/adc.h b/include/adc.h
index 5261c97..ba31ee2 100644
--- a/include/adc.h
+++ b/include/adc.h
@@ -2,5 +2,10 @@
 
 #include <inttypes.h>
 
+#define ADC_M 1024
+extern int16_t adc_buf[ADC_M];
+extern int16_t pADC;
+extern uint8_t fADC;
+
 void adc0_Init();
 int16_t adc0_TR_DATA();
diff --git a/include/derivative.h b/include/derivative.h
index c0a3312..b8df5b2 100644
--- a/include/derivative.h
+++ b/include/derivative.h
@@ -27,10 +27,10 @@
         PORT##port->PCR[pin] |= PORT_PCR_PE(0x1);   \
     }
 
-#define ticks_ms (uint32_t)(ticks_10us / 100)
+#define ticks_ms (uint32_t)(ticks_50us / 20)
 
 extern uint32_t CORCLK;
 extern uint32_t BUSCLK;
-extern volatile uint32_t ticks_10us;
+extern volatile uint32_t ticks_50us;
 extern void SysTick_Handler(void);
 extern void UART1_IRQHandler(void);
diff --git a/include/systick.h b/include/systick.h
index ac9b995..66fda6a 100644
--- a/include/systick.h
+++ b/include/systick.h
@@ -16,11 +16,11 @@ static inline bool timer_expired_ms(uint32_t *t, uint32_t prd) {
     return true;                                             // Expired, return true
 }
 
-static inline bool timer_expired_10us(uint32_t *t, uint32_t prd) {
-    if (ticks_10us + prd < *t) *t = 0;                           // Time wrapped? Reset timer
-    if (*t == 0) *t = ticks_10us + prd;                          // First poll? Set expiration
-    if (*t > ticks_10us) return false;                           // Not expired yet, return
-    *t = (ticks_10us - *t) > prd ? ticks_10us + prd : *t + prd;  // Next expiration time
+static inline bool timer_expired_50us(uint32_t *t, uint32_t prd) {
+    if (ticks_50us + prd < *t) *t = 0;                           // Time wrapped? Reset timer
+    if (*t == 0) *t = ticks_50us + prd;                          // First poll? Set expiration
+    if (*t > ticks_50us) return false;                           // Not expired yet, return
+    *t = (ticks_50us - *t) > prd ? ticks_50us + prd : *t + prd;  // Next expiration time
     return true;                                                 // Expired, return true
 }
 
@@ -29,7 +29,7 @@ static inline void delay_ms(uint32_t ms) {
     while (ticks_ms - start < ms) asm("nop");
 }
 
-static inline void delay_10us(uint32_t us) {
-    uint32_t start = ticks_10us;
-    while (ticks_10us - start < us) asm("nop");
+static inline void delay_50us(uint32_t us) {
+    uint32_t start = ticks_50us;
+    while (ticks_50us - start < us) asm("nop");
 }
diff --git a/main.c b/main.c
index dcd45c8..3379d35 100644
--- a/main.c
+++ b/main.c
@@ -6,8 +6,6 @@
 #include <stdio.h>
 #include <string.h>
 
-#define ADC_M 2048
-
 int main(void) {
     // Initialize
     uart_init(UART_MSG, 9600);  // Initialize UART1 with PC
@@ -35,13 +33,14 @@ int main(void) {
     uint16_t pos[x1 - x0 - 1];
     uint16_t x = x0 + 1, y;
     uint32_t timer = 0;
+    fADC = 1;
 
     for (;;) {
-        if (timer_expired_10us(&timer, 5)) {
+        if (timer_expired_50us(&timer, 1)) {
             LCD_DrawPoint(x, pos[x - x0 - 1], BACK_COLOR);
 
-            res = adc0_TR_DATA() - 1550;
-            y = ym + res * (y1 - ym) / ADC_M;
+            res = adc_buf[pADC];
+            y = ym + res * (y1 - ym) / 2048;
             LCD_DrawPoint(x, y, RED);
             LCD_DrawPoint(x, ym, BLACK);
 
diff --git a/src/adc.c b/src/adc.c
index c7b6d1e..764ac50 100644
--- a/src/adc.c
+++ b/src/adc.c
@@ -1,6 +1,10 @@
 #include "adc.h"
 #include "derivative.h"
 
+int16_t adc_buf[ADC_M];
+int16_t pADC = 0;
+uint8_t fADC = 0;
+
 void adc0_Init() {
     // Enable ADC0 and PORTE clock
     SIM->SCGC6 |= SIM_SCGC6_ADC0_MASK;
@@ -9,10 +13,10 @@ void adc0_Init() {
     // USE AD0 (ADC0_SE4a)
     PORTE->PCR[21] |= PORT_PCR_MUX(0x0);
 
-    ADC0->CFG1 = ADC_CFG1_ADLSMP_MASK    // Sample time 0 = Short, 1 = Long
+    ADC0->CFG1 = ADC_CFG1_ADLSMP(0x01)   // Sample time 0 = Short, 1 = Long
                  | ADC_CFG1_MODE(0x01);  // Conversion mode 00 = 8-bit, 01 = 12-bit, 10 = 10-bit, 11 = 16-bit
-    ADC0->SC3 = ADC_SC3_ADCO_MASK        // Continuous Conversion if AVGE = 1
-                | ADC_SC3_AVGE_MASK      // Hardware average
+    ADC0->SC3 = ADC_SC3_ADCO(0x01)       // Continuous conversion enable
+                | ADC_SC3_AVGE(0x01)     // Hardware average
                 | ADC_SC3_AVGS(0x01);    // Hardware average 00 = 4 samples, 01 = 8, 10 = 16, 11 = 32
     ADC0->SC1[0] = ADC_SC1_ADCH(0x04);   // Input channel select, AD4a is selected as input
 }
diff --git a/src/derivative.c b/src/derivative.c
index 8757269..922085c 100644
--- a/src/derivative.c
+++ b/src/derivative.c
@@ -1,12 +1,19 @@
+#include "adc.h"
 #include "derivative.h"
 #include "uart.h"
 
 uint32_t CORCLK = CORCLK_DEFAULT;
 uint32_t BUSCLK = BUSCLK_DEFAULT;
 
-volatile uint32_t ticks_10us;
+volatile uint32_t ticks_50us;
 
-void SysTick_Handler(void) { ticks_10us++; }
+void SysTick_Handler(void) {
+    ticks_50us++;
+    if (fADC) {
+        adc_buf[pADC] = adc0_TR_DATA() - 1550;
+        pADC = (pADC + 1) % ADC_M;
+    }
+}
 
 void UART1_IRQHandler(void) {
     if (UART1->S1 & UART_S1_RDRF_MASK) {
diff --git a/src/startup.c b/src/startup.c
index 1fee318..61ea36d 100644
--- a/src/startup.c
+++ b/src/startup.c
@@ -159,7 +159,7 @@ __attribute__((naked, noreturn)) void _reset(void) {
     copy_data();
     clock_init();
 
-    SysTick_Config(CORCLK / 100000);  // Period of systick timer : 10 us
+    SysTick_Config(CORCLK / 100000 * 5);  // Period of systick timer : 50 us
 
     main();
     for (;;) (void)0;