[modules] Update ADC temperature to be configurable (#1607)

conf/modules/temp_adc.xml

@@ -5,11 +5,18 @@
     <description>
       Temperature ADC
       Measure temperature of 3 sensores connecter to any ADC
-      Can read LM35 or 10k / 100k NTC sensor
+      Can read LM35 or NTC sensor
     </description>
     <define name="TEMP_ADC_CHANNELX" value="ADC_X" description="choose which ADC is used for temperature sensor"/>
     <define name="TEMP_ADC_CHANNELX_TYPE" value="XXXX" description="choose which type of sensor is used (LM35 or NTC)"/>
   </doc>
+  <settings>
+    <dl_settings>
+      <dl_settings name="temp_adc">
+        <dl_setting min="0" max="1" step="1" module="sensors/temp_adc" var="temp_adc_sync_send" shortname="sync_send" param="TEMP_ADC_SYNC_SEND"  values="Off|On"/>
+      </dl_settings>
+    </dl_settings>
+  </settings>
   <header>
     <file name="temp_adc.h"/>
   </header>

sw/airborne/mcu_periph/adc.h

@@ -45,6 +45,15 @@
  microcontroller architecture.
 */
 
+/* Set the correct ADC resolution */
+#ifndef ADC_RESOLUTION
+#if defined(STM32F1) || defined(STM32F4)
+#define ADC_RESOLUTION 4096
+#else
+#define ADC_RESOLUTION 1024
+#endif
+#endif
+
 /**
     Struct to collect samples from ADC and building an average
     over MAX_AV_NB_SAMPLE values.

sw/airborne/modules/sensors/temp_adc.c

@@ -31,7 +31,8 @@
 #include "subsystems/datalink/downlink.h"
 #include BOARD_CONFIG
 
-float temp_c1, temp_c2, temp_c3;
+bool temp_adc_sync_send = false;
+static float temp_c1, temp_c2, temp_c3;
 
 #if PERIODIC_TELEMETRY
 #include "subsystems/datalink/telemetry.h"
@@ -48,26 +49,28 @@ float temp_c1, temp_c2, temp_c3;
 #endif
 #endif
 
+#ifdef TEMP_ADC_CHANNEL1
+static struct adc_buf temp_buf1;
+
 #ifndef TEMP_ADC_CHANNEL1_TYPE
 #define TEMP_ADC_CHANNEL1_TYPE LM35
 #endif
-#ifndef TEMP_ADC_CHANNEL2_TYPE
-#define TEMP_ADC_CHANNEL2_TYPE LM35
-#endif
-#ifndef TEMP_ADC_CHANNEL3_TYPE
-#define TEMP_ADC_CHANNEL3_TYPE LM35
-#endif
-
-#ifdef TEMP_ADC_CHANNEL1
-static struct adc_buf temp_buf1;
 #endif
 
 #ifdef TEMP_ADC_CHANNEL2
 static struct adc_buf temp_buf2;
+
+#ifndef TEMP_ADC_CHANNEL2_TYPE
+#define TEMP_ADC_CHANNEL2_TYPE LM35
+#endif
 #endif
 
 #ifdef TEMP_ADC_CHANNEL3
 static struct adc_buf temp_buf3;
+
+#ifndef TEMP_ADC_CHANNEL3_TYPE
+#define TEMP_ADC_CHANNEL3_TYPE LM35
+#endif
 #endif
 
 #ifndef TEMP_ADC_NB_SAMPLES
@@ -81,19 +84,22 @@ static struct adc_buf temp_buf3;
 #define TEMP_ADC_SYNC_SEND FALSE
 #endif
 
-float calc_ntc(int16_t raw_temp)
+/**
+ * Calculate the NTC tempreature in celcius based on the Steinhart equation
+ */
+static inline float calc_ntc(int16_t raw_adc, uint16_t pull_up_r, float a, float b, float c)
 {
-  float temp_c;
-  //calc for NTC
-  temp_c = log(((10240000 / raw_temp) - 10000) * 10);
-  //temp_c = 1/(0.001129148+(0.000234125*temp_c)+(0.0000000876741*temp_c*temp_c*temp_c));
-  temp_c = 1 / (0.000603985662844 + (0.000229995493730 * temp_c) + (0.000000067653027 * temp_c *
-                temp_c * temp_c));
-  temp_c = temp_c - 273.15; //convert do celcius
+  // Calculate the logaritmic resistance value based on the Pull up resistor
+  float log_r = log((pull_up_r * raw_adc) / (ADC_RESOLUTION - raw_adc));
+
+  // Steinhart equation (https://en.wikipedia.org/wiki/Steinhart%E2%80%93Hart_equation)
+  // 1 / T = a + b*len(R) + c*ln(R)³
+  float temp_c = 1 / (a + (b * log_r) + (c * log_r * log_r * log_r));
+  temp_c = temp_c - 273.15; // Convert do celcius
   return temp_c;
 }
 
-float calc_lm35(int16_t raw_temp)
+static inline float calc_lm35(int16_t raw_temp)
 {
   return ((float)raw_temp * (3300.0f / 1024.0f) / 10.0f);
 }
@@ -103,6 +109,9 @@ static void temp_adc_downlink(struct transport_tx *trans, struct link_device *de
   pprz_msg_send_TEMP_ADC(trans, dev, AC_ID, &temp_c1, &temp_c2, &temp_c3);
 }
 
+/**
+ * Temperature ADC initialize channels
+ */
 void temp_adc_init(void)
 {
   temp_adc_sync_send = TEMP_ADC_SYNC_SEND;
@@ -134,7 +143,8 @@ void temp_adc_periodic(void)
 #if TEMP_ADC_CHANNEL1_TYPE == LM35
   temp_c1 = calc_lm35(adc_raw);
 #elif TEMP_ADC_CHANNEL1_TYPE == NTC
-  temp_c1 = calc_ntc(adc_raw);
+  temp_c1 = calc_ntc(adc_raw, TEMP_ADC_CHANNEL1_PU_R,
+                     TEMP_ADC_CHANNEL1_A, TEMP_ADC_CHANNEL1_B, TEMP_ADC_CHANNEL1_C);
 #endif
 #endif
 
@@ -143,7 +153,8 @@ void temp_adc_periodic(void)
 #if TEMP_ADC_CHANNEL2_TYPE == LM35
   temp_c2 = calc_lm35(adc_raw);
 #elif TEMP_ADC_CHANNEL2_TYPE == NTC
-  temp_c2 = calc_ntc(adc_raw);
+  temp_c2 = calc_ntc(adc_raw, TEMP_ADC_CHANNEL2_PU_R,
+                     TEMP_ADC_CHANNEL2_A, TEMP_ADC_CHANNEL2_B, TEMP_ADC_CHANNEL2_C);
 #endif
 #endif
 
@@ -152,12 +163,13 @@ void temp_adc_periodic(void)
 #if TEMP_ADC_CHANNEL3_TYPE == LM35
   temp_c3 = calc_lm35(adc_raw);
 #elif TEMP_ADC_CHANNEL3_TYPE == NTC
-  temp_c3 = calc_ntc(adc_raw);
+  temp_c3 = calc_ntc(adc_raw, TEMP_ADC_CHANNEL3_PU_R,
+                     TEMP_ADC_CHANNEL3_A, TEMP_ADC_CHANNEL3_B, TEMP_ADC_CHANNEL3_C);
 #endif
 #endif
 
+  /* Send measurements as soon as they are calculated */
   if (temp_adc_sync_send) {
     temp_adc_downlink(&(DefaultChannel).trans_tx, &(DefaultDevice).device);
   }
-
 }

sw/airborne/modules/sensors/temp_adc.h

@@ -28,12 +28,7 @@
 
 #include "std.h"
 
-/// flag to enable sending every new measurement via telemetry
-bool temp_adc_sync_send;
-
-float calc_ntc(int16_t raw_temp);
-float calc_lm35(int16_t raw_temp);
-
+extern bool temp_adc_sync_send;
 void temp_adc_init(void);
 void temp_adc_periodic(void);