From 35588d46bdd2e6752b8dbdc6fb5b0d7bea36ccd0 Mon Sep 17 00:00:00 2001
From: Benjamin Valentin <benjamin.valentin@ml-pa.com>
Date: Mon, 2 May 2022 16:23:49 +0200
Subject: [PATCH] cpu/sam0_common: adc: Automatically configure extref pin

---
 cpu/sam0_common/include/periph_cpu_common.h | 17 +++++++++++++++++
 cpu/sam0_common/periph/adc.c                | 15 +++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/cpu/sam0_common/include/periph_cpu_common.h b/cpu/sam0_common/include/periph_cpu_common.h
index 1fbee3702d..2ac09a5053 100644
--- a/cpu/sam0_common/include/periph_cpu_common.h
+++ b/cpu/sam0_common/include/periph_cpu_common.h
@@ -779,6 +779,23 @@ typedef struct {
 #endif
 } adc_conf_chan_t;
 
+/**
+ * @brief Pin that can be used for external voltage reference A
+ */
+#define ADC_REFSEL_AREFA_PIN    GPIO_PIN(PA, 3)
+
+/**
+ * @brief Pin that can be used for external voltage reference B
+ */
+#define ADC_REFSEL_AREFB_PIN    GPIO_PIN(PA, 4)
+
+#if defined(ADC_REFCTRL_REFSEL_AREFC) || DOXYGEN
+/**
+ * @brief Pin that can be used for external voltage reference C
+ */
+#define ADC_REFSEL_AREFC_PIN    GPIO_PIN(PA, 6)
+#endif
+
 /**
  * @name Ethernet peripheral parameters
  * @{
diff --git a/cpu/sam0_common/periph/adc.c b/cpu/sam0_common/periph/adc.c
index 8de70b0fa5..cf6871d3e0 100644
--- a/cpu/sam0_common/periph/adc.c
+++ b/cpu/sam0_common/periph/adc.c
@@ -223,6 +223,21 @@ static int _adc_configure(Adc *dev, adc_res_t res)
         SUPC->VREF.reg |= SUPC_VREF_VREFOE;
     }
 #endif
+#ifdef ADC_REFCTRL_REFSEL_AREFA
+    if (ADC_REF_DEFAULT == ADC_REFCTRL_REFSEL_AREFA) {
+        gpio_init_mux(ADC_REFSEL_AREFA_PIN, GPIO_MUX_B);
+    }
+#endif
+#ifdef ADC_REFCTRL_REFSEL_AREFB
+    if (ADC_REF_DEFAULT == ADC_REFCTRL_REFSEL_AREFB) {
+        gpio_init_mux(ADC_REFSEL_AREFB_PIN, GPIO_MUX_B);
+    }
+#endif
+#ifdef ADC_REFCTRL_REFSEL_AREFC
+    if (ADC_REF_DEFAULT == ADC_REFCTRL_REFSEL_AREFC) {
+        gpio_init_mux(ADC_REFSEL_AREFC_PIN, GPIO_MUX_B);
+    }
+#endif
 
     /*  Enable ADC Module */
     dev->CTRLA.reg |= ADC_CTRLA_ENABLE;