Bulmus, A., Freiwald, A., and Wunderlich, C., "Over the Air Software Update Realization within Generic Modules with Microcontrollers Using External Serial FLASH," SAE Technical Paper 2017-01-1613, 2017, doi:10.4271/2017-01-1613.
Connecting mobile communication channels to vehicles’ networks is currently attracting engineers in a wide range. Herein the desire of vehicle manufacturers to remotely execute software updates over the air (SOTA) within electronic control units (ECU) is probably the field of highest attention at the moment.Today software updates are typically done at vehicle service stations and connection the vehicles electronic network via the onboard diagnosis (OBD) interface to a service computer. Herby the duration of the update is invisible to the user, as this happens during standard service appointments. With introduction of SOTA, these updates become very convenient to the customer and can lead to higher customer satisfaction levels. SOTA can be made transparent to the user however the method of implementation can affect the user experience. Currently the range of solutions for data storage to address SOTA ranges from: 1Central Storage Approach whereby external Non-Volatile Memory (NVM) at this device and distributed via the internal car networks to the respective module to be updated.2Localized storage external to the Microcontroller of the device being updated.3Localized storage within the Microcontroller with an “A/B Swap” with separate Linker Scripts4Localized storage internal to the Microcontroller of the device being updated supporting a so called “Ideal A/B Swap” approach.These solutions directly correlate with the duration of the switching time between software versions resulting in differing user experiences. In principle the closer the updated software is stored to the microcontroller, the shorter the time for the update. Additionally a solution may dictate as well new hardware capability in the microcontroller, i.e. the Ideal A/B Swap is the fastest approach and not all microcontrollers on the market today can support this method.A compromise to implement a convenient SOTA user experience is to have additional external serial non-volatile memory attached to the microcontroller within an electronic control unit. The duration and handling of the software update would still allow for a high customer satisfaction.The study starts with a short overview of the operation and activities for updating software within a vehicle. Next, a hardware and software architecture overview is given for the SOTA methods available. Followed by an in depth focus on the implementation method using external non-volatile memory at the microcontroller being updated. In conclusion performance analyses of the data flow for each of the solution from the central storage to the external non-volatile memory to the internal FLASH of the microcontroller. Herby the following aspects for implementation and performance measurements are considered: 1Communication to central storage via the internal bus (CAN or CAN-FD) based on UDS2Security AspectsaCentral Storage to external non-volatile FLASHbExternal non-volatile FLASH and internal FLASHcImage Check before update activation3Fall back scenarios