platforms/digilent_nexys_video: add PMOD connectors

Author: spersvold

litex_boards/platforms/digilent_nexys_video.py

@@ -180,6 +180,9 @@
 # Connectors ---------------------------------------------------------------------------------------
 
 _connectors = [
+    ("pmoda", "AB22 AB21 AB20 AB18 Y21 AA21 AA20 AA18"),
+    ("pmodb", "V9 V8 V7 W7 W9 Y9 Y8 Y7"),
+    ("pmodc", "Y6 AA6 AA8 AB8 R6 T6 AB7 AB6"),
     ("LPC", {
         "DP0_C2M_P"     : "D7",
         "DP0_C2M_N"     : "C7",
@@ -263,6 +266,22 @@
     )
 ]
 
+# PMODS --------------------------------------------------------------------------------------------
+
+def raw_pmod_io(pmod):
+    return [(pmod, 0, Pins(" ".join([f"{pmod}:{i:d}" for i in range(8)])), IOStandard("LVCMOS33"))]
+
+def usb_pmod_io(pmod):
+    return [
+        # USB-UART PMOD: https://store.digilentinc.com/pmod-usbuart-usb-to-uart-interface/
+        ("usb_uart", 0,
+            Subsignal("tx", Pins(f"{pmod}:1")),
+            Subsignal("rx", Pins(f"{pmod}:2")),
+            IOStandard("LVCMOS33")
+        ),
+    ]
+_usb_uart_pmod_io = usb_pmod_io("pmodb") # USB-UART PMOD on JB.
+
 # Platform -----------------------------------------------------------------------------------------
 
 class Platform(Xilinx7SeriesPlatform):