cores/led: add LedChaser (now that LiteX is running on FPGA mining boards let's use fancy led blinks :))

litex/soc/cores/led.py

@@ -0,0 +1,35 @@
+# This file is Copyright (c) 2020 Florent Kermarrec <florent@enjoy-digital.fr>
+# License: BSD
+
+from migen import *
+from migen.genlib.misc import WaitTimer
+
+from litex.soc.interconnect.csr import *
+
+# Led Chaser ---------------------------------------------------------------------------------------
+
+class LedChaser(Module, AutoCSR):
+    def __init__(self, pads, sys_clk_freq, period=1e0):
+        self.control  = CSRStorage(fields=[
+            CSRField("mode", size=2, values=[
+                ("``0b0``", "Chaser mode."),
+                ("``0b1``", "CPU mode."),
+            ])
+        ])
+        self.value = CSRStorage(len(pads), description="Control value when in CPU mode.")
+
+        # # #
+
+        n      = len(pads)
+        chaser = Signal(n)
+        timer  = WaitTimer(int(period*sys_clk_freq/(2*n)))
+        self.submodules += timer
+        self.comb += timer.wait.eq(~timer.done)
+        self.sync += If(timer.done, chaser.eq(Cat(~chaser[-1], chaser)))
+        self.comb += [
+            If(self.control.fields.mode,
+                pads.eq(self.value.storage)
+            ).Else(
+                pads.eq(chaser)
+            )
+        ]