Photon Hard Fault! (Variable randomly changes value and overflows)

Troubleshooting
1

I have a device setup to retrieve information from varies sensors.

For example:

double PCBTemp = 0, AcColdTemp = 0, AcHeatTemp = 0, mainLEDTemp = 0, frontLEDTemp = 0, rearLEDTemp = 0;
int ac_status = 0;
int pump_spd = 0;

They are being updated once every 2 seconds.

Upon creating a lot of variables with many different types(approximately 100+ variables), without any function modifying a variable such as “pump_spd”. When printing, the variable “pump_spd” would display the initial value 0. Without a repeatable pattern, it would suddenly display a value such as 93765147083248.29 when I am debugging using

printf("pump_spd: %d", pump_spd);

Then the photon would flash the red SOS for HARD FAULT.

Will appreciate if anyone could think of the possible reason why this would occur!

2

Hard faults typically indicate that you write a variable past its boundary. It sounds like a variable is being modified past the variable memory boundary. You say you don’t have any functions modifying pump_spd; does your code modify any other variable? For example, are you writing to an array past the defined array boundary and inadvertently modifying pump_spd by that other variable update?

By the way, the variable you typed “93765147083248.29” has a decimal place… is that true? When using %d in printf, it is valid for both decimal and integer according to this reference… but I’m not sure how would get a decimal if declared as an integer. Perhaps you have defined two variables with the same name… maybe even one global and one local?

1 Like
3

Just a point of curiosity: Since the Photon by default hasn’t set a stdout device to write to, where would you expect printf() to print to?

4

‘’‘Serial.printf()’’’ was what I meant and using a serial console from the computer to read it.