From e3509fc0239a88cf74166468db82f68644ca17d5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fabian=20H=C3=BC=C3=9Fler?= <fabian.huessler@st.ovgu.de>
Date: Sun, 23 Jan 2022 10:40:51 +0100
Subject: [PATCH] cpu/stm32: add sampling time to F4/F7 ADC driver

---
 cpu/stm32/periph/adc_f4_f7.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/cpu/stm32/periph/adc_f4_f7.c b/cpu/stm32/periph/adc_f4_f7.c
index 64c489a6b1..a36a80282a 100644
--- a/cpu/stm32/periph/adc_f4_f7.c
+++ b/cpu/stm32/periph/adc_f4_f7.c
@@ -30,6 +30,12 @@
  */
 #define MAX_ADC_SPEED           (12000000U)
 
+/**
+ * @brief   Maximum sampling time for each channel (480 cycles)
+ *          T_CONV[µs] = (RESOLUTION[bits] + SMP[cycles]) / CLOCK_SPEED[MHz]
+ */
+#define MAX_ADC_SMP             (7u)
+
 /**
  * @brief   Default VBAT undefined value
  */
@@ -93,7 +99,15 @@ int adc_init(adc_t line)
         }
     }
     ADC->CCR = ((clk_div / 2) - 1) << 16;
-
+    /* set sampling time to the maximum */
+    if (adc_config[line].chan >= 10) {
+        dev(line)->SMPR1 &= ~(MAX_ADC_SMP << (3 * (adc_config[line].chan - 10)));
+        dev(line)->SMPR1 |= MAX_ADC_SMP << (3 * (adc_config[line].chan - 10));
+    }
+    else {
+        dev(line)->SMPR1 &= ~(MAX_ADC_SMP << (3 * adc_config[line].chan));
+        dev(line)->SMPR2 |= MAX_ADC_SMP << (3 * adc_config[line].chan);
+    }
     /* free the device again */
     done(line);
     return 0;