Merge pull request #683 from ajs123/master

Add SAADC offset calibration and reading of CPU temperature

Author: hathach

cores/nRF5/wiring.c

@@ -143,3 +143,27 @@ void systemOff(uint32_t pin, uint8_t wake_logic)
     NRF_POWER->SYSTEMOFF = 1;
   }
 }
+
+
+float readCPUTemperature( void )
+{
+  uint8_t en;
+  int32_t temp;
+  (void) sd_softdevice_is_enabled(&en);
+  if (en) 
+  {
+    sd_temp_get(&temp);
+  }
+  else
+  {
+    NRF_TEMP->EVENTS_DATARDY = 0x00; // Only needed in case another function is also looking at this event flag
+    NRF_TEMP->TASKS_START = 0x01; 
+  
+    while (!NRF_TEMP->EVENTS_DATARDY);
+    temp = NRF_TEMP->TEMP;                      // Per anomaly 29 (unclear whether still applicable), TASKS_STOP will clear the TEMP register.
+
+    NRF_TEMP->TASKS_STOP = 0x01;           // Per anomaly 30 (unclear whether still applicable), the temp peripheral needs to be shut down
+    NRF_TEMP->EVENTS_DATARDY = 0x00;
+  }
+  return temp / 4.0F;
+}

cores/nRF5/wiring.h

@@ -42,6 +42,12 @@ static inline bool isInISR(void)
   return (SCB->ICSR & SCB_ICSR_VECTACTIVE_Msk) != 0 ;
 }
 
+/*
+ * \brief Reads the on-chip temperature sensor, returning the temperature in degrees C
+ * with a resolution of 0.25 degrees.
+*/
+float readCPUTemperature( void );
+
 #ifdef __cplusplus
 }
 #endif

cores/nRF5/wiring_analog.h

@@ -116,6 +116,14 @@ extern void analogWriteResolution(uint8_t res);
  */
 extern void analogSampleTime(uint8_t sTime);
 
+/*
+ * \brief Calibrate the ADC offset. This is recommended occasionally, or any time the
+ * chip temperature changes by more than 10 C.  See the SAADC section of the Nordic
+ * nrf52 product pecification.
+ * 
+ */
+extern void analogCalibrateOffset( void );
+
 extern void analogOutputInit( void ) ;
 
 #ifdef __cplusplus

cores/nRF5/wiring_analog_nRF52.c

@@ -284,6 +284,25 @@ uint32_t analogReadVDD( void )
   return analogRead_internal(SAADC_CH_PSELP_PSELP_VDD);
 }
 
+void analogCalibrateOffset( void )
+{
+  // Enable the SAADC
+  NRF_SAADC->ENABLE = 0x01;
+
+  // Be sure the done flag is cleared, then trigger offset calibration
+  NRF_SAADC->EVENTS_CALIBRATEDONE = 0x00;
+  NRF_SAADC->TASKS_CALIBRATEOFFSET = 0x01;
+
+  // Wait for completion
+  while (!NRF_SAADC->EVENTS_CALIBRATEDONE);
+
+  // Clear the done flag  (really shouldn't have to do this both times)
+  NRF_SAADC->EVENTS_CALIBRATEDONE = 0x00;
+
+  // Disable the SAADC
+  NRF_SAADC->ENABLE = 0x00;
+}
+
 #ifdef __cplusplus
 }
 #endif