Diff: main.cpp

Revision:

0:44f87c90421e

Child:

1:aef8ec8d23d8

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Fri Nov 20 15:13:10 2020 +0000
@@ -0,0 +1,59 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2019 ARM Limited
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include "mbed.h"
+#include "platform/mbed_thread.h"
+#include "stdio.h"
+/* Reference resistor in series with the thermistor is of 10 KOhm */
+#define R_REFERENCE (float)(10000)
+/* Beta constant of this thermistor is 3380 Kelvin. See the thermistor
+   (NCP18XH103F03RB) data sheet for more details. */
+#define B_CONSTANT (float)(3380)
+/* Resistance of the thermistor is 10K at 25 degrees C (from data sheet)
+   Therefore R0 = 10000 Ohm, and T0 = 298.15 Kelvin, which gives
+   R_INFINITY = R0 e^(-B_CONSTANT / T0) = 0.1192855 */
+#define R_INFINITY (float)(0.1192855)
+/* Zero Kelvin in degree C */
+#define ABSOLUTE_ZERO (float)(-273.15)
+//static DigitalIn thermVDD(P10_0);  // if wing is detached and powered from 3.3v
+//static DigitalIn thermGND(P10_3);  // don't need to control power to thermistor
+   
+
+// Blinking rate in milliseconds
+#define BLINKING_RATE_MS 500
+#define SW2 P0_4
+
+int main()
+{
+    // Initialise the digital pin LED1 as an output
+    DigitalOut led(LED1);
+    DigitalIn pushButton(SW2, PullUp);
+    AnalogIn vTherm(P10_1);
+    DigitalOut thermVcc(P10_3);
+    DigitalOut thermGnd(P10_0);
+    
+    thermVcc = 1;
+    thermGnd = 0;
+    while (true) {
+        if (pushButton == 0) {
+            led = !led;
+            /* read thermistor Voltage */
+    float refVoltage = vTherm.read() * 2.4; // Range of ADC 0->2*Vref
+    float refCurrent = refVoltage  / 10000.0; // 10k Reference Resistor
+    float thermVoltage = 3.3 - refVoltage;    // Assume supply voltage is 3.3v
+    float thermResistance = thermVoltage / refCurrent; 
+    float logrT = (float32_t)log((float64_t)thermResistance);
+ 
+    /* Calculate temperature from the resistance of thermistor using Steinhart-Hart Equation */
+    float stEqn = (float32_t)((0.0009032679) + ((0.000248772) * logrT) + 
+                             ((2.041094E-07) * pow((float64)logrT, (float32)3)));
+ 
+    float temperatureC = (float32_t)(((1.0 / stEqn) - 273.15)  + 0.5);
+
+            printf("Temperature is %f\r\n", temperatureC);
+        }
+        thread_sleep_for(BLINKING_RATE_MS);
+    }
+}