Add a VREFBUF Driver Module to control the reference voltage.

zephyr/modules/owntech_vrefbuf_driver/zephyr/CMakeLists.txt

+if(CONFIG_OWNTECH_VREFBUF_DRIVER)
+  # Define the current folder as a Zephyr library
+  zephyr_library()
+  # Select source files to be compiled
+  zephyr_library_sources(
+    ./src/vrefbuf_driver.c
+    )
+endif()

zephyr/modules/owntech_vrefbuf_driver/zephyr/Kconfig

+config OWNTECH_VREFBUF_DRIVER
+	bool "Enable OwnTech VREFBUF driver for STM32"
+	default y

zephyr/modules/owntech_vrefbuf_driver/zephyr/module.yml

+name: owntech_vrefbuf_driver
+build:
+  cmake: zephyr
+  kconfig: zephyr/Kconfig

zephyr/modules/owntech_vrefbuf_driver/zephyr/src/vrefbuf_driver.c

+/*
+ * Copyright (c) 2021 LAAS-CNRS
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU Lesser General Public License as published by
+ *   the Free Software Foundation, either version 2.1 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU Lesser General Public License for more details.
+ *
+ *   You should have received a copy of the GNU Lesser General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: LGLPV2.1
+ */
+
+/**
+ * @author  Clément Foucher <clement.foucher@laas.fr>
+ */
+
+
+// Zephyr
+#include <zephyr.h>
+#include <device.h>
+
+// STM32 LL
+#include "stm32_ll_bus.h"
+#include "stm32_ll_system.h"
+
+
+static int vrefbuf_init(const struct device* dev)
+{
+	LL_APB2_GRP1_EnableClock(LL_APB2_GRP1_PERIPH_SYSCFG);
+	LL_VREFBUF_SetVoltageScaling(LL_VREFBUF_VOLTAGE_SCALE0);
+	LL_VREFBUF_DisableHIZ();
+	LL_VREFBUF_Enable();
+
+	return 0;
+}
+
+DEVICE_DEFINE(vrefbuf_driver,
+              "vrefbuf_driver",
+              vrefbuf_init,
+              device_pm_control_nop,
+              NULL,
+              NULL,
+              PRE_KERNEL_1,
+              CONFIG_KERNEL_INIT_PRIORITY_DEVICE,
+              NULL
+             );

zephyr/prj.conf

@@ -45,3 +45,4 @@ CONFIG_ASSERT=y
 #CONFIG_OWNTECH_LEG_DRIVER=n
 #CONFIG_OWNTECH_NGND_DRIVER=n
 #CONFIG_OWNTECH_DATA_ACQUISITION=n
+#CONFIG_OWNTECH_VREFBUF_DRIVER=n