- if(trstate == 0) {
- if(tron && zok && (mnow > ztime + trdelay)) {
- PORTD |= 1;
- zok = 0;
- trstate = 1;
- trtime = mnow;
- }
- } else if(trstate == 1) {
- if(mnow > trtime + 500) {
- PORTD &= ~1;
- trstate = 0;
+ static char state = 0;
+ static unsigned long last = 0;
+ static float a, ra, l, t;
+
+ /*
+ * Theoretically:
+ * t = RC * ln(2) => R = t / (C * ln(2))
+ * R = A * exp(B / T) => T = B / ln(R / A)
+ * T = B / ln(t / (A * C * ln(2)))
+ * Where:
+ * t = The measured time (s)
+ * R = The resistance of the thermistor (Ohm)
+ * C = The capacitance of the capacitor (F)
+ * T = The temperature (K)
+ * A, B are the thermistor-specific constants
+ *
+ * In the following code:
+ * a = ttimea as float
+ * C = 1e-6 / (A * C * ln(2))
+ * ra = a * C
+ * l = ln(ra)
+ * t = B / l
+ * Note, temperature is in Kelvin
+ */
+#define C 10.819112 /* A is 0.1333469 */
+#define B 4020.0
+ if(state == 0) {
+ if((mnow - last > 200000) && tavgok) {
+ a = (float)ttimea;
+ state = 1;
+ tavgok = 0;
+ last = mnow;