VOLVO+ Development Story (10), camping mode

Camping mode

VOLVO XC60 is suitable for camping. Some customers told me they're unloading. Several minutes later, the tailgate can't close anymore



Opps, I didn't test the scearuo before. Here is the engineering report:
  • The car put idle, and several minutes, both car and VOLVO+ go to sleep mode
  • In sleep mode, VOLVO+ wakes up every 3 seconds (3000ms). The on duration is roughly 10ms to detect packets on the CAN bus. It shall detect packet then enter active mode
Therefore, humans shall press the tailgate button in the 10ms window, whose probability is 10/3000 = 0.3% (1 success in 300 trials). Try to tweak parameters:
  1. Every second (1000ms) listens 10ms. Success rate 1%. 1 success in 100 trial, too bad
  2. Every seconds (1000ms) listens 500ms. Success rate 50%. 1 success in 2 trials. Extremely bad power consumption
  3. VOLVO+ enters sleep 10 minutes later after cars entering sleep mode. It sacrifices some battery life, but not solves the problem (why can't I have a party with tailgate on?)
So my low power mechanism failed completedly. I read the MCU datasheet carefully, and I got something useful:
  1. CAN transceiver can monitor the bus in power-saving way. With any dominant signal appeared, it will notify MCU
  2. MCU wakes up immediately if receiving notification signal from CAN transceiver
So the problem is resolved, and the low power mechanism improved as well
  • Wake up speed (<1ms), much faster than old mechanism (10~3000x). A single CAN packet wakes up system
  • Slightly improved standby power drain: 1% battery can keeps standby in 2 years
I've notified all shipped VOLVO+ owner to upgrade the FW. I will take charge of shipping fees







Maybe I should go camping too, so that the design can be more comprehensive

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