First doc writeup

docs/DEVELOPMENT_SETUP.md

@@ -0,0 +1,49 @@
+# Current Development Setup
+
+This file holds the current `CM7` development setup and implementation specificities. The target architecture is documented in [`ARCHITECTURE.md`](./ARCHITECTURE.md).
+
+## Platform
+
+Current bench development targets the STM32H747 on the Arduino Giga platform.
+
+The present `CM7` code uses:
+
+- STM32 HAL
+- FreeRTOS
+- CMSIS-RTOS v2
+- `TIM2` as the main engine-control timer
+
+The current pin mapping is provisional:
+
+- `TIM2_CH1` / `PA0`: crank input capture
+- `TIM2_CH2` / `PA1`: cam input capture
+- `TIM2_CH3` / `PA2`: scheduled spark output compare
+
+## Implementation Specificities
+
+### Spark Charge Step
+
+The current spark path forces a charge transition before scheduling the release transition. This is temporary and belongs to the development setup, not the target architecture.
+
+The final design should handle dwell time explicitly:
+
+- compute when charging must begin
+- compute when spark must release
+- schedule both as normal output-compare transitions
+
+### Injection Placeholder
+
+Injection scheduling is not complete. `tasks/crank.c` contains an early placeholder based on `INJECTION_PHASE`, but there is no finished actuator path yet.
+
+### Sync Filtering
+
+The broad sync model is implemented, but thresholds and recovery behavior still need hardware validation. Current behavior includes:
+
+- `SYNC_NOT_OK`, `SYNC_PENDING`, and `SYNC_OK`
+- limited cam miss tolerance through `MAX_CAM_MISS`
+- crank interval filtering while synchronized
+- sync loss when cam timing is inconsistent with the expected crank state
+
+### Timer and Pin Routing
+
+`TIM2` and the current Arduino Giga pins are useful for bench work. They should not be treated as final ECU hardware routing.