Add tempmon, fixes #323

teensy4/core_pins.h

 void rtc_set(unsigned long t);
 void rtc_compensate(int adjust);
 
+void tempmon_init(void);
+float tempmonGetTemp(void);
+void tempmon_Start();
+void tempmon_Stop();
+void tempmon_PwrDwn();
+
 #ifdef __cplusplus
 }
 

teensy4/startup.c

 void usb_pll_start();
 extern void analog_init(void); // analog.c
 extern void pwm_init(void); // pwm.c
+extern void tempmon_init(void);  //tempmon.c
 uint32_t set_arm_clock(uint32_t frequency); // clockspeed.c
 extern void __libc_init_array(void); // C++ standard library
 
 	usb_init();
 	analog_init();
 	pwm_init();
+	tempmon_init();
 
 	while (millis() < 300) ; // wait at least 300ms before calling user code
 	printf("before C++ constructors\n");

teensy4/tempmon.c

+#include "imxrt.h"
+#include "core_pins.h"
+#include "debug/printf.h"
+
+
+static uint16_t frequency = 0x03U;
+static uint32_t highAlarmTemp   = 85U;
+static uint32_t lowAlarmTemp    = 25U;
+static uint32_t panicAlarmTemp  = 90U;
+
+static uint32_t s_hotTemp, s_hotCount, s_roomC_hotC;
+static float s_hot_ROOM;
+
+void tempmon_init(void)
+{
+  // Notes:
+  //    TEMPMON_TEMPSENSE0 &= ~0x2U;  Stops temp monitoring
+  //    TEMPMON_TEMPSENSE0 |= 0x1U;   Powers down temp monitoring 
+  uint32_t calibrationData;
+  uint32_t roomCount;
+  uint32_t tempCodeVal;
+      
+  //first power on the temperature sensor - no register change
+  TEMPMON_TEMPSENSE0 &= ~0x1U;
+
+  //set monitoring frequency - no register change
+  TEMPMON_TEMPSENSE1 = (((uint32_t)(((uint32_t)(frequency)) << 0U)) & 0xFFFFU);
+  
+  //read calibration data - this works
+  calibrationData = HW_OCOTP_ANA1;
+    s_hotTemp = (uint32_t)(calibrationData & 0xFFU) >> 0x00U;
+    s_hotCount = (uint32_t)(calibrationData & 0xFFF00U) >> 0X08U;
+    roomCount = (uint32_t)(calibrationData & 0xFFF00000U) >> 0x14U;
+    s_hot_ROOM = s_hotTemp - 25.0f;
+    s_roomC_hotC = roomCount - s_hotCount;
+
+    //time to set alarm temperatures
+  //Set High Alarm Temp
+  tempCodeVal = (uint32_t)(s_hotCount + (s_hotTemp - highAlarmTemp) * s_roomC_hotC / s_hot_ROOM);
+    TEMPMON_TEMPSENSE0 |= (((uint32_t)(((uint32_t)(tempCodeVal)) << 20U)) & 0xFFF00000U);
+  
+  //Set Panic Alarm Temp
+  tempCodeVal = (uint32_t)(s_hotCount + (s_hotTemp - panicAlarmTemp) * s_roomC_hotC / s_hot_ROOM);
+    TEMPMON_TEMPSENSE2 |= (((uint32_t)(((uint32_t)(tempCodeVal)) << 16U)) & 0xFFF0000U);
+  
+  // Set Low Temp Alarm Temp
+  tempCodeVal = (uint32_t)(s_hotCount + (s_hotTemp - lowAlarmTemp) * s_roomC_hotC / s_hot_ROOM);
+    TEMPMON_TEMPSENSE2 |= (((uint32_t)(((uint32_t)(tempCodeVal)) << 0U)) & 0xFFFU);
+  
+  //Start temp monitoring
+  TEMPMON_TEMPSENSE0 |= 0x2U;   //starts temp monitoring
+}
+
+
+float tempmonGetTemp(void)
+{
+    uint32_t nmeas;
+    float tmeas;
+
+    while (!(TEMPMON_TEMPSENSE0 & 0x4U))
+    {
+    }
+
+    /* ready to read temperature code value */
+    nmeas = (TEMPMON_TEMPSENSE0 & 0xFFF00U) >> 8U;
+    /* Calculate temperature */
+    tmeas = s_hotTemp - (float)((nmeas - s_hotCount) * s_hot_ROOM / s_roomC_hotC);
+
+    return tmeas;
+}
+
+void tempmon_Start()
+{
+    TEMPMON_TEMPSENSE0 |= 0x2U;
+}
+
+void tempmon_Stop()
+{
+    TEMPMON_TEMPSENSE0 &= ~0x2U;
+}
+
+void tempmon_PwrDwn()
+{
+    TEMPMON_TEMPSENSE0 |= 0x1U;
+}