diff --git a/Inc/stm32h7xx_hal_conf.h b/Inc/stm32h7xx_hal_conf.h
index ed7bc0a..4846dee 100644
--- a/Inc/stm32h7xx_hal_conf.h
+++ b/Inc/stm32h7xx_hal_conf.h
@@ -107,7 +107,7 @@
   *        (when HSE is used as system clock source, directly or through the PLL).
   */
 #if !defined  (HSE_VALUE)
-#define HSE_VALUE    (2 * 8000000UL) /*!< Value of the External oscillator in Hz */
+#define HSE_VALUE    (8000000UL) /*!< Value of the External oscillator in Hz */
 #endif /* HSE_VALUE */
 
 #if !defined  (HSE_STARTUP_TIMEOUT)
diff --git a/README.md b/README.md
index dd2bdcc..0460c30 100644
--- a/README.md
+++ b/README.md
@@ -83,6 +83,10 @@ The firmware prints its messages to and expect user input coming on the board co
 
 The 1PPS signal is emitted on the `PB5` pin.
 
+## Test environment
+
+To test the software and evaluate the synchronization accuracy connect the devboard with another PTP-compatible equipment, either a dedicated Master clock or any other device (e.g. another devboard). We recommend using the [linuxptp](https://github.com/richardcochran/linuxptp) software suite available in Linux systems through the official package repositories, PTP hardware support is available out-of-the-box on several Intel NICs, like Intel I210, Intel I219-V or Intel 82576.
+
 ## Development
 
 An all-around [Visual Studio Code](https://code.visualstudio.com/) project is packaged along the project to enable easy development, debugging and editing. To enable these powerful features, install the [STM32Cube for Visual Studio Code](https://marketplace.visualstudio.com/items?itemName=stmicroelectronics.stm32-vscode-extension), [CMakeTools](https://marketplace.visualstudio.com/items?itemName=ms-vscode.cmake-tools), [Cortex-Debug](https://marketplace.visualstudio.com/items?itemName=marus25.cortex-debug), [Embedded Tools](https://marketplace.visualstudio.com/items?itemName=ms-vscode.vscode-embedded-tools) extensions, [OpenOCD](https://openocd.org/) and the [STM32CubeCLT](https://www.st.com/en/development-tools/stm32cubeclt.html) software package. The latter one is required for downloading the firmware right away using the Cortex-Debug extension (if not done through OpenOCD) and for providing the Embedded Tools extension with register description `.SVD` files. [clangd](https://marketplace.visualstudio.com/items?itemName=llvm-vs-code-extensions.vscode-clangd) and clang-format are highly recommended.