cores.opto.tof: Add polling core for VL6180X

lambdalib/cores/opto/tof.py

@@ -0,0 +1,60 @@
+"""Time-of-flight related cores"""
+
+from amaranth import *
+
+from lambdalib.cores.i2c.stream import I2CStream
+from lambdalib.interface.stream import Endpoint
+from lambdalib.time.timer import WaitTimer
+
+
+__all__ = ["VL6180XPoller"]
+
+
+class VL6180XPoller(Elaboratable):
+    def __init__(self, pins, sys_freq, i2c_freq=400e6, poll_freq=1e3):
+        self._pins = pins
+        self._sys_freq = sys_freq
+        self._i2c_freq = i2c_freq
+        self._poll_freq = poll_freq
+
+        self.samples = stream.Endpoint([("data", 8)])
+
+    def elaborate(self, platform):
+        m = Module()
+
+        m.submodules.i2c = i2c = I2CStream(
+            pins=self._pins,
+            period_cyc=self._sys_freq / self._i2c_freq,
+        )
+
+        # Power up timer
+        m.submodules.pup_timer = pup_timer = WaitTimer(self._sys_freq * 1.4e-3)  # 1.4ms delay (Power-Up Delay + Boot time)
+
+        # Polling pulse generator
+        polling_interval_cycles = self._sys_freq / self._poll_freq
+        polling_cnt = Signal(range(polling_interval_cycles))
+        with m.If(polling_cnt == 0):
+            m.d.sync += polling_cnt.eq(polling_interval_cycles - 1)
+        with m.Else():
+            m.d.sync += polling_cnt.eq(polling_cnt - 1)
+
+        # Routine from Fig 11/Fig 12 of VL6180X datasheet
+        with m.FSM():
+            with m.State("POWER-UP"):
+                with m.If(pup_timer.done):
+                    m.next = "WAIT-DEVICE-BOOTED"
+
+            with m.State("INIT-DATA"):
+                pass
+
+            with m.State("PREPARE"):
+                pass
+
+            with m.State("WAIT-POLLING-PULSE"):
+                with m.If(polling_cnt == 0):
+                    m.next = "RANGE-POLL"
+
+            with m.State("RANGE-POLL"):
+                pass
+
+        return m