diff --git a/app/hal.h b/app/hal.h
index ead2af9..d21e365 100644
--- a/app/hal.h
+++ b/app/hal.h
@@ -63,7 +63,6 @@ typedef enum {
 
 hal_err_t hal_uart_send(hal_uart_port_t port, const uint8_t* data, size_t len);
 
-
 // Crypto (only use in crypto library)
 hal_err_t hal_rng_next(uint8_t *buf, size_t len);
 
@@ -79,4 +78,7 @@ hal_err_t hal_crc32_update(hal_crc32_ctx_t* ctx, const uint8_t* data, size_t len
 hal_err_t hal_crc32_finish(hal_crc32_ctx_t* ctx, uint32_t *out);
 #endif
 
+// Timer
+hal_err_t hal_delay_us(uint32_t usec);
+
 #endif
diff --git a/app/iso7816/smartcard.c b/app/iso7816/smartcard.c
index eba13a5..06751ef 100644
--- a/app/iso7816/smartcard.c
+++ b/app/iso7816/smartcard.c
@@ -4,6 +4,7 @@
 #include "iso7816/t1.h"
 #include "FreeRTOS.h"
 #include "task.h"
+#include "hal.h"
 
 #define SC_RESET_DELAY 400
 #define SC_DEFAULT_ETU10NS 9300
@@ -17,11 +18,10 @@ static inline void SmartCard_State_Reset(SmartCard* sc) {
 void SmartCard_Delay(SmartCard* sc, uint32_t etu) {
   uint32_t usec = (sc->etu_10ns * etu)/100;
 
-  if (usec & 0xffff0000) {
+  if (usec > 4000) {
     vTaskDelay(pdMS_TO_TICKS(usec/1000));
   } else {
-    //sc->usec_timer->Instance->CNT = 0;
-    //while (sc->usec_timer->Instance->CNT < usec);
+    hal_delay_us(usec);
   }
 }
 
@@ -138,38 +138,4 @@ uint8_t SmartCard_Send_APDU(SmartCard* sc, APDU* apdu) {
     return 0;
   }
 }
-/*
-void HAL_SMARTCARD_ErrorCallback(SMARTCARD_HandleTypeDef *hsc) {
-  uint32_t error = HAL_SMARTCARD_GetError(hsc);
 
-  if(error & HAL_SMARTCARD_ERROR_FE) {
-    __HAL_SMARTCARD_FLUSH_DRREGISTER(hsc);
-  }
-
-  if(error & HAL_SMARTCARD_ERROR_PE) {
-    __HAL_SMARTCARD_ENABLE_IT(hsc, SMARTCARD_IT_RXNE);
-    __HAL_SMARTCARD_FLUSH_DRREGISTER(hsc);
-  }
-
-  if(error & HAL_SMARTCARD_ERROR_NE) {
-    __HAL_SMARTCARD_FLUSH_DRREGISTER(hsc);
-  }
-
-  if(error & HAL_SMARTCARD_ERROR_ORE) {
-    __HAL_SMARTCARD_FLUSH_DRREGISTER(hsc);
-  }
-
-  if(error & HAL_SMARTCARD_ERROR_RTO) {
-    __HAL_SMARTCARD_FLUSH_DRREGISTER(hsc);
-    __HAL_SMARTCARD_DISABLE_IT(hsc, SMARTCARD_IT_RTO);
-  }
-
-}
-
-void HAL_SMARTCARD_TxCpltCallback(SMARTCARD_HandleTypeDef *hsc) {
-
-}
-
-void HAL_SMARTCARD_RxCpltCallback(SMARTCARD_HandleTypeDef *hsc) {
-  __HAL_SMARTCARD_DISABLE_IT(hsc, SMARTCARD_IT_RTO);
-}*/
diff --git a/nxp/source/nxp.c b/nxp/source/nxp.c
index f288aa5..8c3bfe7 100644
--- a/nxp/source/nxp.c
+++ b/nxp/source/nxp.c
@@ -42,6 +42,7 @@
 #include "fsl_trng.h"
 #include "fsl_lpuart.h"
 #include "fsl_dcp.h"
+#include "fsl_gpt.h"
 #include "hal.h"
 
 struct gpio_pin_spec {
@@ -77,6 +78,14 @@ hal_err_t hal_init(void) {
 
   sha256_handle.channel = kDCP_Channel0;
 
+  gpt_config_t gptCfg;
+  GPT_GetDefaultConfig(&gptCfg);
+  gptCfg.clockSource = kGPT_ClockSource_Osc;
+  gptCfg.enableFreeRun = true;
+  gptCfg.enableMode = true;
+  gptCfg.divider = 24;
+  GPT_Init(GPT1, &gptCfg);
+
   return HAL_OK;
 }
 
@@ -112,3 +121,9 @@ hal_err_t hal_uart_send(hal_uart_port_t port, const uint8_t* data, size_t len) {
   return LPUART_WriteBlocking(BOARD_DEBUG_UART_BASEADDR, data, len) == kStatus_Success ? HAL_OK : HAL_ERROR;
 }
 
+hal_err_t hal_delay_us(uint32_t usec) {
+  GPT_StartTimer(GPT1);
+  while(GPT_GetCurrentTimerCount(GPT1) < usec) {}
+  GPT_StopTimer(GPT1);
+  return HAL_OK;
+}