unoq: implement analogReference

Take into account the analog switch

Author: facchinm

cores/arduino/zephyrCommon.cpp

@@ -353,7 +353,7 @@ void analogWrite(enum dacPins dacName, int value) {
 
 #ifdef CONFIG_ADC
 
-void analogReference(uint8_t mode) {
+void __attribute__((weak)) analogReference(uint8_t mode) {
 	/*
 	 * The Arduino API not clearly defined what means of
 	 * the mode argument of analogReference().

loader/fixups.c

@@ -186,23 +186,63 @@ SYS_INIT(maybe_flash_bootloader, POST_KERNEL, CONFIG_FILE_SYSTEM_INIT_PRIORITY);
 #include <stm32_ll_adc.h>
 #include <zephyr/devicetree.h>
 
-static int enable_adc_reference(void) {
+int analog_reference(uint8_t reference) {
 	uint8_t init_status;
-	/* VREF+ is not connected to VDDA by default */
-	/* Use 2.5V as reference (instead of 3.3V) for internal channels
-	 * calculation
-	 */
+	/* VREF+ is connected to VDDA by default */
+	const struct gpio_dt_spec spec =
+		GPIO_DT_SPEC_GET_BY_IDX(DT_PATH(zephyr_user), analog_switch_gpios, 0);
+
+	gpio_pin_configure_dt(&spec, GPIO_OUTPUT);
+
 	__HAL_RCC_SYSCFG_CLK_ENABLE();
+	__HAL_RCC_VREF_CLK_ENABLE();
+
+	HAL_SYSCFG_VREFBUF_HighImpedanceConfig(SYSCFG_VREFBUF_HIGH_IMPEDANCE_ENABLE);
+	HAL_SYSCFG_DisableVREFBUF();
+
+	if (reference == AR_DEFAULT) {
+		/* VREF+ is connected to VDDA */
+		gpio_pin_set_dt(&spec, 0);
+		return;
+	}
+
+	gpio_pin_set_dt(&spec, 1);
 
-	/* VREF_OUT2 = 2.5 V */
-	HAL_SYSCFG_VREFBUF_VoltageScalingConfig(SYSCFG_VREFBUF_VOLTAGE_SCALE1);
+	if (reference == AR_EXTERNAL) {
+		return 0;
+	}
+
+	uint32_t voltageScaling = SYSCFG_VREFBUF_VOLTAGE_SCALE3;
+	switch (reference) {
+	case AR_INTERNAL2V5:
+		voltageScaling = SYSCFG_VREFBUF_VOLTAGE_SCALE3;
+		break;
+	case AR_INTERNAL2V05:
+		voltageScaling = SYSCFG_VREFBUF_VOLTAGE_SCALE2;
+		break;
+	case AR_INTERNAL1V8:
+		voltageScaling = SYSCFG_VREFBUF_VOLTAGE_SCALE1;
+		break;
+	case AR_INTERNAL1V5:
+		voltageScaling = SYSCFG_VREFBUF_VOLTAGE_SCALE0;
+		break;
+	}
+
+	HAL_SYSCFG_VREFBUF_VoltageScalingConfig(voltageScaling);
+	HAL_SYSCFG_EnableVREFBUF();
 	HAL_SYSCFG_VREFBUF_HighImpedanceConfig(SYSCFG_VREFBUF_HIGH_IMPEDANCE_DISABLE);
 
-	init_status = HAL_SYSCFG_EnableVREFBUF();
 	__ASSERT(init_status == HAL_OK, "ADC Conversion value may be incorrect");
 
 	return init_status;
 }
 
-SYS_INIT(enable_adc_reference, POST_KERNEL, 0);
+EXPORT_SYMBOL(analog_reference);
+
+int disable_vrefbuf() {
+	// This is the safe HW configuration
+	analog_reference(AR_DEFAULT);
+}
+
+SYS_INIT(disable_vrefbuf, POST_KERNEL, 0);
 #endif

variants/arduino_uno_q_stm32u585xx/analogReference.cpp

@@ -0,0 +1,10 @@
+#include <Arduino.h>
+
+extern "C" {
+    int analog_reference(uint8_t mode);
+};
+
+void analogReference(uint8_t mode)
+{
+  analog_reference(mode);
+}

variants/arduino_uno_q_stm32u585xx/arduino_uno_q_stm32u585xx.overlay

@@ -162,6 +162,7 @@
 				    <&gpiof 9 GPIO_ACTIVE_HIGH>,
 				    <&gpiof 10 GPIO_ACTIVE_HIGH>,
 				    <&gpiog 13 GPIO_ACTIVE_HIGH>,       /* Internal SPI RDY */
+				    <&gpioa 2 GPIO_ACTIVE_HIGH>,        /* Analog switch for VREF */
 				    <&gpioh 3 GPIO_ACTIVE_HIGH>;        /* BOOT0 */
 
 		builtin-led-gpios = <&gpioh 10 GPIO_ACTIVE_HIGH>,
@@ -186,6 +187,7 @@
 		pwms = <>;
 
 		control-gpios = <&gpiog 13 GPIO_ACTIVE_HIGH>;    /* Internal SPI RDY */
+		analog-switch-gpios = <&gpioa 2 GPIO_ACTIVE_HIGH>;    /* Analog switch for VREF */
 
 		io-channels =	<&adc1 9>,
 				<&adc1 10>,

variants/arduino_uno_q_stm32u585xx/variant.h

@@ -11,3 +11,11 @@
 #define SS      0
 #define SDA     0
 #define SCL     0
+
+#define AR_DEFAULT          0
+#define AR_INTERNAL2V5      1
+#define AR_INTERNAL2V05     2
+#define AR_INTERNAL1V5      3
+#define AR_INTERNAL1V8      4
+#define AR_EXTERNAL         5
+#define AR_INTERNAL         AR_INTERNAL2V5