message: annotate GPIO list
diff: @@ -144,14 +144,14 @@ std::array<Axis, AXIS_COUNT> axes{{
  Stm32Gpio gpios[] = {
  {nullptr, 0}, // dummy GPIO0 so that PCB labels and software numbers match
  - {GPIOB, GPIO_PIN_2},
  - {GPIOA, GPIO_PIN_5},
  - {GPIOA, GPIO_PIN_4},
  - {GPIOA, GPIO_PIN_3},
  - {nullptr, 0},
  - {nullptr, 0},
  - {nullptr, 0},
  - {nullptr, 0},
  + {GPIOB, GPIO_PIN_2}, // GPIO1
  + {GPIOA, GPIO_PIN_5}, // GPIO2
  + {GPIOA, GPIO_PIN_4}, // GPIO3
  + {GPIOA, GPIO_PIN_3}, // GPIO4
  + {nullptr, 0}, // GPIO5 (doesn't exist on this board)
  + {nullptr, 0}, // GPIO6 (doesn't exist on this board)
  + {nullptr, 0}, // GPIO7 (doesn't exist on this board)
  + {nullptr, 0}, // GPIO8 (doesn't exist on this board)
  {GPIOB, GPIO_PIN_4}, // ENC0_A
  {GPIOB, GPIO_PIN_5}, // ENC0_B
  @@ -166,14 +166,14 @@ Stm32Gpio gpios[] = {
  Stm32Gpio gpios[] = {
  {nullptr, 0}, // dummy GPIO0 so that PCB labels and software numbers match
  - {GPIOA, GPIO_PIN_0},
  - {GPIOA, GPIO_PIN_1},
  - {GPIOA, GPIO_PIN_2},
  - {GPIOA, GPIO_PIN_3},
  - {GPIOB, GPIO_PIN_2},
  - {nullptr, 0},
  - {nullptr, 0},
  - {nullptr, 0},
  + {GPIOA, GPIO_PIN_0}, // GPIO1
  + {GPIOA, GPIO_PIN_1}, // GPIO2
  + {GPIOA, GPIO_PIN_2}, // GPIO3
  + {GPIOA, GPIO_PIN_3}, // GPIO4
  + {GPIOB, GPIO_PIN_2}, // GPIO5
  + {nullptr, 0}, // GPIO6 (doesn't exist on this board)
  + {nullptr, 0}, // GPIO7 (doesn't exist on this board)
  + {nullptr, 0}, // GPIO8 (doesn't exist on this board)
  {GPIOB, GPIO_PIN_4}, // ENC0_A
  {GPIOB, GPIO_PIN_5}, // ENC0_B
  @@ -188,14 +188,14 @@ Stm32Gpio gpios[] = {
  Stm32Gpio gpios[GPIO_COUNT] = {
  {nullptr, 0}, // dummy GPIO0 so that PCB labels and software numbers match
  - {GPIOA, GPIO_PIN_0},
  - {GPIOA, GPIO_PIN_1},
  - {GPIOA, GPIO_PIN_2},
  - {GPIOA, GPIO_PIN_3},
  - {GPIOC, GPIO_PIN_4},
  - {GPIOB, GPIO_PIN_2},
  - {GPIOA, GPIO_PIN_15},
  - {GPIOB, GPIO_PIN_3},
  + {GPIOA, GPIO_PIN_0}, // GPIO1
  + {GPIOA, GPIO_PIN_1}, // GPIO2
  + {GPIOA, GPIO_PIN_2}, // GPIO3
  + {GPIOA, GPIO_PIN_3}, // GPIO4
  + {GPIOC, GPIO_PIN_4}, // GPIO5
  + {GPIOB, GPIO_PIN_2}, // GPIO6
  + {GPIOA, GPIO_PIN_15}, // GPIO7
  + {GPIOB, GPIO_PIN_3}, // GPIO8
  {GPIOB, GPIO_PIN_4}, // ENC0_A
  {GPIOB, GPIO_PIN_5}, // ENC0_B
  