1 files changed, 64 insertions, 0 deletions
diff --git a/usrp2/fpga/control_lib/simple_uart_rx.v b/usrp2/fpga/control_lib/simple_uart_rx.v
new file mode 100644
index 000000000..debdd618b
--- /dev/null
+++ b/usrp2/fpga/control_lib/simple_uart_rx.v
@@ -0,0 +1,64 @@
+
+
+module simple_uart_rx
+  #(parameter DEPTH=0)
+    (input clk, input rst, 
+     output [7:0] fifo_out, input fifo_read, output [7:0] fifo_level, output fifo_empty, 
+     input [15:0] clkdiv, input rx);
+
+   reg 		  rx_d1, rx_d2;
+   always @(posedge clk)
+     if(rst)
+       {rx_d2,rx_d1} <= 0;
+     else
+       {rx_d2,rx_d1} <= {rx_d1,rx};
+   
+   reg [15:0] 	  baud_ctr;
+   reg [3:0] 	  bit_ctr;
+   reg [7:0] 	  sr;
+
+   wire 	  neg_trans = rx_d2 & ~rx_d1;
+   wire 	  shift_now = baud_ctr == (clkdiv>>1);
+   wire 	  stop_now = (bit_ctr == 10) && shift_now;
+   wire 	  go_now = (bit_ctr == 0) && neg_trans;
+   
+   always @(posedge clk)
+     if(rst)
+       sr <= 0;
+     else if(shift_now)
+       sr <= {rx_d2,sr[7:1]};
+   
+   always @(posedge clk)
+     if(rst)
+       baud_ctr <= 0;
+     else
+       if(go_now)
+	 baud_ctr <= 1;
+       else if(stop_now)
+	 baud_ctr <= 0;
+       else if(baud_ctr >= clkdiv)
+	 baud_ctr <= 1;
+       else if(baud_ctr != 0)
+	 baud_ctr <= baud_ctr + 1;
+
+   always @(posedge clk)
+     if(rst)
+       bit_ctr <= 0;
+     else 
+       if(go_now)
+	 bit_ctr <= 1;
+       else if(stop_now)
+	 bit_ctr <= 0;
+       else if(baud_ctr == clkdiv)
+	 bit_ctr <= bit_ctr + 1;
+   
+   wire 	  full;
+   wire 	  write = ~full & rx_d2 & stop_now;
+   
+   medfifo #(.WIDTH(8),.DEPTH(DEPTH)) fifo
+     (.clk(clk),.rst(rst),
+      .datain(sr),.write(write),.full(full),
+      .dataout(fifo_out),.read(fifo_read),.empty(fifo_empty),
+      .clear(0),.space(),.occupied(fifo_level) );
+   
+endmodule // simple_uart_rx