A health checking library.
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This library is basically a panic mode button for embedded systems. In embedded application system resets are usually very fast and not very disruptive as most applications are simply tasks waiting for a given event to happen. So when something goes very wrong and it is very hard to recover from it (like running out of memory) resetting the microcontroller and re-initializing the application is a good way to get back to a known good state.

We built this library for our satellite firmware.

libohnoes is a (for now) FreeRTOS dependent library that runs a monitoring task periodically checking the health of your application and when something goes very wrong it resets the microcontroller so it returns to a known state.

The health-checking functions have to be registered using the libohnoes interface, they should return a boolean true (C99), if they return false, libohnoes will reset the system.


  • FreeRTOS


typedef bool (*ohnoes_health_check_fn)(void);

Health checking callback. Takes no parameters and returns a boolean.

typedef void (*ohnoes_cpu_reset)(void);

CPU reset function, this is heavily microcontroller/architecture dependent so you should provide it. Takes no parameters and returns nothing.


int ohnoes_init (int frequency_secs, ohnoes_cpu_reset cpu_reset, int priority)

Initializes the ohnoes health check library. frequency_secs is the number of seconds to wait between health checks, cpu_reset is the function that will reset the cpu and priority is the priority for the FreeRTOS task.

void ohnoes_destroy (void)

Destroys the ohnoes task and removes all the registered health checking functions from internal data structures.

void ohnoes_pause (void)

Stops monitoring. The task still exists and is scheduled to run, just does nothing and yields to other tasks.

void ohnoes_unpause (void)

Resumes monitoring after a call to pause.

int ohnoes_register_health_check (ohnoes_health_check_fn check)

Registers a health check function. The function must take no parameters and return a boolean. true means everything is fine, false means something is very wrong and it will make libohnoes reset the system. Even if there are several registered functions, if one of them returns false, it will reset the system so make sure the functions do check for really unrecoverable situations.