cores/i2c: add a driver for the tca9548a i2c multiplexer

lambdalib/cores/i2c/tca9548a.py

@@ -0,0 +1,65 @@
+# 2024 - LambdaConcept - [email protected]
+
+from amaranth import *
+
+from ...interface import stream
+from ..i2c.stream import *
+
+
+__all__ = ["TCA9548A"]
+
+
+class TCA9548A(Elaboratable):
+    """ Driver for TCA9548A I2C multiplexer.
+
+    On `self.ctrl` change, an I2C write is triggered to update
+    the control register of the TCA9548A multiplexer:
+        byte 0: i2c_addr
+        byte 1: ctrl byte
+
+    This module `source` stream is intented to be connected to an existing
+    I2CStream instance through a stream arbiter.
+    """
+    def __init__(self, i2c_addr=0x70):
+        self.i2c_addr = i2c_addr
+
+        self.done   = Signal()
+        self.ctrl   = Signal(8)
+        self.source = stream.Endpoint(i2c_stream_description)
+
+    def elaborate(self, platform):
+        source = self.source
+
+        m = Module()
+
+        init        = Signal()
+        ctrl_r      = Signal.like(self.ctrl)
+        ctrl_addr_n = Signal()
+
+        update      = (self.ctrl != ctrl_r)
+
+        with m.FSM():
+            with m.State("IDLE"):
+                with m.If(~init):
+                    m.d.sync += init.eq(1)
+                    m.next = "MUX"
+                with m.Elif(update):
+                    m.d.sync += ctrl_r.eq(self.ctrl)
+                    m.next = "MUX"
+                with m.Else():
+                    m.d.comb += self.done.eq(1)
+
+            with m.State("MUX"):
+                m.d.comb += [
+                    source.r_wn .eq(0), # Write
+                    source.data .eq(Mux(~ctrl_addr_n,
+                                        self.i2c_addr << 1, ctrl_r)),
+                    source.last .eq(ctrl_addr_n),
+                    source.valid.eq(1),
+                ]
+                with m.If(source.valid & source.ready):
+                    m.d.sync += ctrl_addr_n.eq(~ctrl_addr_n)
+                    with m.If(source.last):
+                        m.next = "IDLE"
+
+        return m