diff --git a/ion/test/device/n0110/Makefile b/ion/test/device/n0110/Makefile
index 3acf290d9..d379f0fb2 100644
--- a/ion/test/device/n0110/Makefile
+++ b/ion/test/device/n0110/Makefile
@@ -1,10 +1,8 @@
 test_ion_external_flash_read_src += $(addprefix ion/test/$(PLATFORM)/$(MODEL)/, \
-  external_flash_helper.cpp \
   external_flash_read.cpp \
 )
 
 test_ion_external_flash_write_src += $(addprefix ion/test/$(PLATFORM)/$(MODEL)/, \
-  external_flash_helper.cpp \
   external_flash_write.cpp \
 )
 
diff --git a/ion/test/device/n0110/external_flash_helper.cpp b/ion/test/device/n0110/external_flash_helper.cpp
deleted file mode 100644
index 11d776784..000000000
--- a/ion/test/device/n0110/external_flash_helper.cpp
+++ /dev/null
@@ -1,26 +0,0 @@
-#include "ion/include/ion/timing.h"
-#include <quiz.h>
-#include <stddef.h>
-
-size_t uint64ToString(uint64_t n, char buffer[]) {
-  size_t len = 0;
-  do {
-    buffer[len++] = (n % 10) + '0';
-  } while ((n /= 10) > 0);
-  int i = 0;
-  int j = len - 1;
-  while (i < j) {
-    char c = buffer[i];
-    buffer[i++] = buffer[j];
-    buffer[j--] = c;
-  }
-  return len;
-}
-
-void printElapsedTime(uint64_t startTime) {
-  char buffer[7+26+2] = " time: ";
-  size_t len = uint64ToString((Ion::Timing::millis() - startTime)/1000, buffer+7);
-  buffer[7+len] = 's';
-  buffer[7+len+1] = 0;
-  quiz_print(buffer);
-}
diff --git a/ion/test/device/n0110/external_flash_helper.h b/ion/test/device/n0110/external_flash_helper.h
index de84d3d0d..11350ce9b 100644
--- a/ion/test/device/n0110/external_flash_helper.h
+++ b/ion/test/device/n0110/external_flash_helper.h
@@ -17,6 +17,3 @@ inline uint32_t expected_value_at(uint32_t * ptr) {
   uint16_t * ptr16 = reinterpret_cast<uint16_t *>(ptr);
   return (static_cast<uint32_t>(expected_value_at(ptr16+1)) << 16) + static_cast<uint32_t>(expected_value_at(ptr16));
 }
-
-size_t uint64ToString(uint64_t n, char buffer[]);
-void printElapsedTime(uint64_t startTime);
diff --git a/ion/test/device/n0110/external_flash_read.cpp b/ion/test/device/n0110/external_flash_read.cpp
index 3b234f14c..4a2417c6e 100644
--- a/ion/test/device/n0110/external_flash_read.cpp
+++ b/ion/test/device/n0110/external_flash_read.cpp
@@ -1,7 +1,6 @@
 #include <quiz.h>
+#include <quiz/stopwatch.h>
 #include <ion.h>
-#include <assert.h>
-#include <drivers/config/external_flash.h>
 #include <drivers/external_flash.h>
 #include "external_flash_helper.h"
 
@@ -47,56 +46,56 @@ void test(int accessType, int repeat) {
 }
 
 QUIZ_CASE(ion_extflash_read_byte_fwd) {
-  uint64_t startTime = Ion::Timing::millis();
+  uint64_t startTime = quiz_stopwatch_start();
   test<uint8_t>(0, 1);
-  printElapsedTime(startTime);
+  quiz_stopwatch_print_lap(startTime);
 }
 
 QUIZ_CASE(ion_extflash_read_byte_bck) {
-  uint64_t startTime = Ion::Timing::millis();
+  uint64_t startTime = quiz_stopwatch_start();
   test<uint8_t>(1, 1);
-  printElapsedTime(startTime);
+  quiz_stopwatch_print_lap(startTime);
 }
 
 QUIZ_CASE(ion_extflash_read_byte_rand) {
-  uint64_t startTime = Ion::Timing::millis();
+  uint64_t startTime = quiz_stopwatch_start();
   test<uint8_t>(2, 1);
-  printElapsedTime(startTime);
+  quiz_stopwatch_print_lap(startTime);
 }
 
 QUIZ_CASE(ion_extflash_read_half_fwd) {
-  uint64_t startTime = Ion::Timing::millis();
+  uint64_t startTime = quiz_stopwatch_start();
   test<uint16_t>(0, 1);
-  printElapsedTime(startTime);
+  quiz_stopwatch_print_lap(startTime);
 }
 
 QUIZ_CASE(ion_extflash_read_half_bck) {
-  uint64_t startTime = Ion::Timing::millis();
+  uint64_t startTime = quiz_stopwatch_start();
   test<uint16_t>(1, 1);
-  printElapsedTime(startTime);
+  quiz_stopwatch_print_lap(startTime);
 }
 
 QUIZ_CASE(ion_extflash_read_half_rand) {
-  uint64_t startTime = Ion::Timing::millis();
+  uint64_t startTime = quiz_stopwatch_start();
   test<uint16_t>(2, 1);
-  printElapsedTime(startTime);
+  quiz_stopwatch_print_lap(startTime);
 }
 
 QUIZ_CASE(ion_extflash_read_word_fwd) {
-  uint64_t startTime = Ion::Timing::millis();
+  uint64_t startTime = quiz_stopwatch_start();
   test<uint32_t>(0, 1);
-  printElapsedTime(startTime);
+  quiz_stopwatch_print_lap(startTime);
 }
 
 QUIZ_CASE(ion_extflash_read_word_bck) {
-  uint64_t startTime = Ion::Timing::millis();
+  uint64_t startTime = quiz_stopwatch_start();
   test<uint32_t>(1, 1);
-  printElapsedTime(startTime);
+  quiz_stopwatch_print_lap(startTime);
 }
 
 QUIZ_CASE(ion_extflash_read_word_rand) {
-  uint64_t startTime = Ion::Timing::millis();
+  uint64_t startTime = quiz_stopwatch_start();
   test<uint32_t>(2, 1);
-  printElapsedTime(startTime);
+  quiz_stopwatch_print_lap(startTime);
   Ion::Timing::msleep(3000);
 }
diff --git a/ion/test/device/n0110/external_flash_write.cpp b/ion/test/device/n0110/external_flash_write.cpp
index 0585abd96..a9097117a 100644
--- a/ion/test/device/n0110/external_flash_write.cpp
+++ b/ion/test/device/n0110/external_flash_write.cpp
@@ -1,20 +1,19 @@
 #include <quiz.h>
-#include <drivers/config/external_flash.h>
+#include <quiz/stopwatch.h>
 #include <drivers/external_flash.h>
-#include "ion/include/ion/timing.h"
 #include "external_flash_helper.h"
 
 // Choose some not too uniform data to program the external flash memory with.
 
 QUIZ_CASE(ion_ext_flash_erase) {
-  uint64_t startTime = Ion::Timing::millis();
+  uint64_t startTime = quiz_stopwatch_start();
   Ion::Device::ExternalFlash::MassErase();
-  printElapsedTime(startTime);
+  quiz_stopwatch_print_lap(startTime);
 }
 
 QUIZ_CASE(ion_ext_flash_program) {
   // Program separately each page of the flash memory
-  uint64_t startTime = Ion::Timing::millis();
+  uint64_t startTime = quiz_stopwatch_start();
   for (int page = 0; page < (1<<15); page++) {
     uint8_t buffer[256];
     for (int byte = 0; byte < 256; byte++) {
@@ -22,5 +21,5 @@ QUIZ_CASE(ion_ext_flash_program) {
     }
     Ion::Device::ExternalFlash::WriteMemory(reinterpret_cast<uint8_t *>(page * 256), buffer, 256);
   }
-  printElapsedTime(startTime);
+  quiz_stopwatch_print_lap(startTime);
 }
diff --git a/quiz/Makefile b/quiz/Makefile
index 25ddd96b1..10ffb7e9f 100644
--- a/quiz/Makefile
+++ b/quiz/Makefile
@@ -14,6 +14,7 @@ runner_src += $(addprefix quiz/src/, \
   assertions.cpp \
   i18n.cpp \
   runner.cpp \
+  stopwatch.cpp \
 )
 
 runner_src += $(BUILD_DIR)/quiz/src/tests_symbols.c
diff --git a/quiz/include/quiz/stopwatch.h b/quiz/include/quiz/stopwatch.h
new file mode 100644
index 000000000..53a582b08
--- /dev/null
+++ b/quiz/include/quiz/stopwatch.h
@@ -0,0 +1,17 @@
+#ifndef QUIZ_STOPWATCH_H
+#define QUIZ_STOPWATCH_H
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+uint64_t quiz_stopwatch_start();
+void quiz_stopwatch_print_lap(uint64_t startTime);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/quiz/src/runner.cpp b/quiz/src/runner.cpp
index dae22605a..ef4b883c3 100644
--- a/quiz/src/runner.cpp
+++ b/quiz/src/runner.cpp
@@ -1,8 +1,6 @@
 #include "quiz.h"
 #include "symbols.h"
-#include <string.h>
 #include <ion.h>
-#include <kandinsky.h>
 #include <poincare/init.h>
 #include <poincare/tree_pool.h>
 #include <poincare/exception_checkpoint.h>
diff --git a/quiz/src/stopwatch.cpp b/quiz/src/stopwatch.cpp
new file mode 100644
index 000000000..f4dafac16
--- /dev/null
+++ b/quiz/src/stopwatch.cpp
@@ -0,0 +1,36 @@
+#include <quiz/stopwatch.h>
+#include "quiz.h"
+#include <ion/timing.h>
+#include <string.h>
+
+uint64_t quiz_stopwatch_start() {
+  return Ion::Timing::millis();
+}
+
+static size_t uint64ToString(uint64_t n, char buffer[]) {
+  size_t len = 0;
+  do {
+    buffer[len++] = (n % 10) + '0';
+  } while ((n /= 10) > 0);
+  int i = 0;
+  int j = len - 1;
+  while (i < j) {
+    char c = buffer[i];
+    buffer[i++] = buffer[j];
+    buffer[j--] = c;
+  }
+  return len;
+}
+
+void quiz_stopwatch_print_lap(uint64_t startTime) {
+  constexpr char Time[] = " time: ";
+  constexpr char Ms[] = "ms";
+  constexpr size_t uint64ToStringMaxLength = 20;
+  constexpr size_t MaxLength = sizeof(Time) + uint64ToStringMaxLength + sizeof(Ms) + 1;
+  char buffer[MaxLength];
+  char * position = buffer;
+  position += strlcpy(position, Time, sizeof(Time));
+  position += uint64ToString(Ion::Timing::millis() - startTime, position);
+  position += strlcpy(position, Ms, sizeof(Ms));
+  quiz_print(buffer);
+}