When and why does embedded Electronic Control Unit(ECU) use default calibration values?

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naseeam

Joined Jan 4, 2017
49
Typical embedded ECU stores real calibration values and default calibration values in Non-Volatile Memory(NVM).

Let's say ECU is Steering Controller and it's primary function is Lane Keep Assist(LKA). It is mounted in a commercial truck. It programs camera's real and default calibration values in NVM.

Mostly, real calibration values are used. When and why are default calibration values used?
 

Papabravo

Joined Feb 24, 2006
17,263
Typical embedded ECU stores real calibration values and default calibration values in Non-Volatile Memory(NVM).

Let's say ECU is Steering Controller and it's primary function is Lane Keep Assist(LKA). It is mounted in a commercial truck. It programs camera's real and default calibration values in NVM.

Mostly, real calibration values are used. When and why are default calibration values used?
I don't know that much about how the firmware for a vehicle is made ready for service, but I worked for a company that made industrial control devices. In that environment the devices would be delivered from the factory to a systems integrator. The system integrator would be responsible for installing, testing and commissioning each device in a complex system. The device would actually have four different sets of default parameters. They would be used as follows:
  1. A set of factory default parameters would be located in the FLASH (program) memory for the device. These would only ever be used to initialize a blank or corrupted version of the non-volatile parameters. If the firmware comes up with an uninitialized non-volatile memory the set of FLASH default parameters is copied into the non-volatile. That accounts for two sets.
  2. After commissioning by the systems integrator, a set of user non-volatile default parameters is established in a section of the non-volatile memory. Once the device is released to the customer a copy of the user non-volatile parameters is established as the working set of non-volatile parameters. This working set can be moved if the endurance limit of a section of the non-volatile memory is reached.
  3. At any point in time it is possible to go back to either user non-volatile parameters or the factory default parameters.
If non-volatile updates are done with a script file then restoring the current configuration from either the user-default or the factory default is a nearly automated process.
 
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