From 36aff1e4646ada018512ff0ee0c8a27205d8c260 Mon Sep 17 00:00:00 2001
From: LinFor <linfor@gmail.com>
Date: Tue, 22 Dec 2020 03:30:03 +0300
Subject: [PATCH] 12-bit ADC resolution for STM32 (#20519)

---
 Marlin/src/HAL/STM32/HAL.h                                  | 6 +++---
 Marlin/src/module/thermistor/thermistors.h                  | 2 ++
 .../share/PlatformIO/variants/MARLIN_FYSETC_S6/variant.h    | 2 ++
 3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/Marlin/src/HAL/STM32/HAL.h b/Marlin/src/HAL/STM32/HAL.h
index f2fb5ddb6a..b1c27e4ec5 100644
--- a/Marlin/src/HAL/STM32/HAL.h
+++ b/Marlin/src/HAL/STM32/HAL.h
@@ -159,14 +159,14 @@ static inline int freeMemory() {
 
 #define HAL_ANALOG_SELECT(pin) pinMode(pin, INPUT)
 
-inline void HAL_adc_init() {}
-
 #define HAL_ADC_VREF         3.3
-#define HAL_ADC_RESOLUTION  10
+#define HAL_ADC_RESOLUTION  ADC_RESOLUTION // 12
 #define HAL_START_ADC(pin)  HAL_adc_start_conversion(pin)
 #define HAL_READ_ADC()      HAL_adc_result
 #define HAL_ADC_READY()     true
 
+inline void HAL_adc_init() { analogReadResolution(HAL_ADC_RESOLUTION); }
+
 void HAL_adc_start_conversion(const uint8_t adc_pin);
 
 uint16_t HAL_adc_get_result();
diff --git a/Marlin/src/module/thermistor/thermistors.h b/Marlin/src/module/thermistor/thermistors.h
index 340712e22d..03ed5c2a57 100644
--- a/Marlin/src/module/thermistor/thermistors.h
+++ b/Marlin/src/module/thermistor/thermistors.h
@@ -27,6 +27,8 @@
 #define THERMISTOR_TABLE_SCALE (HAL_ADC_RANGE / _BV(THERMISTOR_TABLE_ADC_RESOLUTION))
 #if ENABLED(HAL_ADC_FILTERED)
   #define OVERSAMPLENR 1
+#elif HAL_ADC_RESOLUTION > 10
+  #define OVERSAMPLENR (20 - HAL_ADC_RESOLUTION)
 #else
   #define OVERSAMPLENR 16
 #endif
diff --git a/buildroot/share/PlatformIO/variants/MARLIN_FYSETC_S6/variant.h b/buildroot/share/PlatformIO/variants/MARLIN_FYSETC_S6/variant.h
index ee4b1ef296..07e2cad3f9 100644
--- a/buildroot/share/PlatformIO/variants/MARLIN_FYSETC_S6/variant.h
+++ b/buildroot/share/PlatformIO/variants/MARLIN_FYSETC_S6/variant.h
@@ -114,6 +114,8 @@ extern "C" {
 #define NUM_ANALOG_INPUTS       7
 #define NUM_ANALOG_FIRST        80
 
+#define ADC_RESOLUTION          12
+
 // PWM resolution
 // #define PWM_RESOLUTION          12
 #define PWM_FREQUENCY           20000 // >= 20 Khz => inaudible noise for fans