temp: Use more sane substitute value

When the ADC saturates, use a substitute value that doesn't kill the
following math...

Misc/Temp-Monitor/temperature_monitor.py

@@ -26,25 +26,28 @@ temperature_filtered = -1
 # Ignore the first 5 seconds
 last_report = time.ticks_ms() + 5000
 while True:
-    raw_value = cs1237.read()
-    value = float(raw_value) / (2**24 - 1)
+    try:
+        raw_value = cs1237.read()
+        value = float(raw_value) / (2**24 - 1)
 
-    if value > 0.9999:
-        value = 0
-    else:
-        value = 10e3 * 1 / (1 / value - 1)
+        if value > 0.9999:
+            value = 20e3
+        else:
+            value = 10e3 * 1 / (1 / value - 1)
 
-    temperature = THERMISTOR_BETA / math.log(value / THERMISTOR_RINF) - 273.15
+        temperature = THERMISTOR_BETA / math.log(value / THERMISTOR_RINF) - 273.15
 
-    if temperature_filtered == -1:
-        temperature_filtered = temperature
+        if temperature_filtered == -1:
+            temperature_filtered = temperature
 
-    temperature_filtered = (
-        temperature_filtered * (1 - FILTER_A) + temperature * FILTER_A
-    )
+        temperature_filtered = (
+            temperature_filtered * (1 - FILTER_A) + temperature * FILTER_A
+        )
 
-    now = time.ticks_ms()
-    elapsed = now - last_report
-    if elapsed >= 200 or elapsed < 0:
-        print(f"{temperature:.6f},{temperature_filtered:.6f}")
-        last_report = now
+        now = time.ticks_ms()
+        elapsed = now - last_report
+        if elapsed >= 200 or elapsed < 0:
+            print(f"{temperature:.6f},{temperature_filtered:.6f}")
+            last_report = now
+    except Exception as e:
+        print(f"Error {e}")