1 files changed, 65 insertions, 0 deletions
diff --git a/fpga/usrp2/models/uart_rx.v b/fpga/usrp2/models/uart_rx.v
new file mode 100644
index 000000000..738ffb45b
--- /dev/null
+++ b/fpga/usrp2/models/uart_rx.v
@@ -0,0 +1,65 @@
+//
+// Copyright 2011 Ettus Research LLC
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+
+
+// Simple printout of characters from the UART
+//   Only does 8N1, requires the baud clock
+
+module uart_rx (input baudclk, input rxd);
+   reg [8:0] sr = 9'b0;
+   reg [3:0]  baud_ctr = 4'b0;
+
+   /*
+   wire       byteclk = baud_ctr[3];
+   reg 	      rxd_d1 = 0;
+   always @(posedge baudclk)
+     rxd_d1 <= rxd;
+   
+   always @(posedge baudclk)
+     if(rxd_d1 != rxd)
+       baud_ctr <= 0;
+     else
+       baud_ctr <= baud_ctr + 1;
+*/
+
+   wire       byteclk = baudclk;
+   
+   always @(posedge byteclk)
+     sr <= { rxd, sr[8:1] };
+
+   reg [3:0]  state = 0;
+   always @(posedge byteclk)
+     case(state)
+       0 : 
+	 if(~sr[8] & sr[7])  // found start bit
+	   state  <= 1;
+       1, 2, 3, 4, 5, 6, 7, 8 :
+	 state <= state + 1;
+       9 : 
+	 begin
+	    state <= 0;
+	    $write("%c",sr[7:0]);
+	    if(~sr[8])
+	      $display("Error, no stop bit\n");
+	 end
+       default :
+	 state <= 0;
+     endcase // case(state)
+
+endmodule // uart_rx
+