pipeline GW: add KCode Dict & add a decode example

src/gateware/cxp_pipeline.py

@@ -13,7 +13,16 @@ downconn_layout = [("data", downconn_dw), ("k", downconn_dw//8)]
 def K(x, y):
     return ((y << 5) | x)
 
-def bytes2word(arr):
+KCode = {
+    "pak_start" : K(27, 7),
+    "io_ack" : K(28, 6), 
+    "trig_indic_28_2" : K(28, 2), 
+    "trig_indic_28_4" : K(28, 4), 
+    "pak_end" : K(29, 7),
+}
+
+
+def _bytes2word(arr):
     assert len(arr) == 4
     sum = 0
     for i, val in enumerate(arr):
@@ -386,7 +395,7 @@ class Receiver_Path(Module, AutoCSR):
 
         
         self.submodules.trig_ack_checker = trig_ack_checker = CXP_Trig_Ack_Checker()
-        self.submodules.packet_decoder= packet_decoder = CXP_Data_Packet_Decode()
+        self.submodules.packet_decoder = packet_decoder = CXP_Data_Packet_Decode()
         self.sync += [
             If(trig_ack_checker.ack,
                self.trig_ack.eq(1),
@@ -412,11 +421,55 @@ class CXP_Data_Packet_Decode(Module):
         # This is where data stream comes out
         self.source = stream.Endpoint(downconn_layout)
 
+        self.packet_type = Signal(8)
+        self.decode_err = Signal()
+
         # # #
 
-        self.comb += self.sink.connect(self.source)
+        # decoder -> priorities mux(normal packet vs trigger ack) -> data packet mux (control ack, data stream, heartbeat, testmode, (optional Genlcam event))
+        type = {
+            "data_stream": 0x01,
+            "control_ack_no_tag": 0x03,
+            "test_packet": 0x04,
+            "control_ack_with_tag": 0x06,
+            "event_ack": 0x08,
+            "heartbeat": 0x09,
 
+            "debug" : 0x02,
+        }
 
+        self.submodules.fsm = fsm = FSM(reset_state="IDLE")
+
+        fsm.act("IDLE",
+            self.sink.ack.eq(1),
+            # TODO: add error correction?
+            If((self.sink.stb & (self.sink.data == _bytes2word([KCode["pak_start"]]*4)) & (self.sink.k == 0b1111)),
+                NextState("DECODE_PAK"),
+            )
+        )
+
+        # TODO: decode packet type here
+        fsm.act("DECODE_PAK",
+            self.sink.ack.eq(1),
+            If(self.sink.stb,
+                NextValue(self.packet_type, self.sink.data[:8]),
+                NextState("STREAMING"),
+            )
+        )
+
+        fsm.act("STREAMING",
+            If((self.sink.stb & (self.sink.data == _bytes2word([KCode["pak_end"]]*4)) & (self.sink.k == 0b1111)),
+                # discard K29,7
+                self.sink.ack.eq(1),
+                NextState("IDLE")
+            ).Elif(self.packet_type == type["debug"],
+                self.sink.connect(self.source),
+            ).Else(
+                # discard K29,7
+                self.sink.ack.eq(1),
+                NextValue(self.decode_err, 1),
+            )
+        )
 class CXP_Trig_Ack_Checker(Module, AutoCSR):
     def __init__(self):
         self.sink = stream.Endpoint(downconn_layout)
@@ -437,7 +490,7 @@ class CXP_Trig_Ack_Checker(Module, AutoCSR):
         )
 
         fsm.act("COPY",
-            If((self.sink.stb & (self.sink.data == bytes2word([K(28, 6)]*4)) & (self.sink.k == 0b1111)),
+            If((self.sink.stb & (self.sink.data == _bytes2word([KCode["io_ack"]]*4)) & (self.sink.k == 0b1111)),
                 # discard K28,6
                 self.sink.ack.eq(1),
                 NextState("CHECK_ACK")
@@ -451,7 +504,7 @@ class CXP_Trig_Ack_Checker(Module, AutoCSR):
                 NextState("IDLE"),
                 # discard the word after K28,6
                 self.sink.ack.eq(1),
-                If(self.sink.data == bytes2word([0x01]*4),
+                If(self.sink.data == _bytes2word([0x01]*4),
                     self.ack.eq(1),
                 )
             )