Merge FPGA repository back into UHD repository

The FPGA codebase was removed from the UHD repository in 2014 to reduce
the size of the repository. However, over the last half-decade, the
split between the repositories has proven more burdensome than it has
been helpful. By merging the FPGA code back, it will be possible to
create atomic commits that touch both FPGA and UHD codebases. Continuous
integration testing is also simplified by merging the repositories,
because it was previously difficult to automatically derive the correct
UHD branch when testing a feature branch on the FPGA repository.

This commit also updates the license files and paths therein.

We are therefore merging the repositories again. Future development for
FPGA code will happen in the same repository as the UHD host code and
MPM code.

== Original Codebase and Rebasing ==

The original FPGA repository will be hosted for the foreseeable future
at its original local location: https://github.com/EttusResearch/fpga/

It can be used for bisecting, reference, and a more detailed history.

The final commit from said repository to be merged here is
05003794e2da61cabf64dd278c45685a7abad7ec. This commit is tagged as
v4.0.0.0-pre-uhd-merge.

If you have changes in the FPGA repository that you want to rebase onto
the UHD repository, simply run the following commands:

- Create a directory to store patches (this should be an empty
  directory):

    mkdir ~/patches

- Now make sure that your FPGA codebase is based on the same state as
  the code that was merged:

    cd src/fpga # Or wherever your FPGA code is stored
    git rebase v4.0.0.0-pre-uhd-merge

  Note: The rebase command may look slightly different depending on what
  exactly you're trying to rebase.

- Create a patch set for your changes versus v4.0.0.0-pre-uhd-merge:

    git format-patch v4.0.0.0-pre-uhd-merge -o ~/patches

  Note: Make sure that only patches are stored in your output directory.
  It should otherwise be empty. Make sure that you picked the correct
  range of commits, and only commits you wanted to rebase were exported
  as patch files.

- Go to the UHD repository and apply the patches:

    cd src/uhd # Or wherever your UHD repository is stored
    git am --directory fpga ~/patches/*
    rm -rf ~/patches # This is for cleanup

== Contributors ==

The following people have contributed mainly to these files (this list
is not complete):

Co-authored-by: Alex Williams <alex.williams@ni.com>
Co-authored-by: Andrej Rode <andrej.rode@ettus.com>
Co-authored-by: Ashish Chaudhari <ashish@ettus.com>
Co-authored-by: Ben Hilburn <ben.hilburn@ettus.com>
Co-authored-by: Ciro Nishiguchi <ciro.nishiguchi@ni.com>
Co-authored-by: Daniel Jepson <daniel.jepson@ni.com>
Co-authored-by: Derek Kozel <derek.kozel@ettus.com>
Co-authored-by: EJ Kreinar <ej@he360.com>
Co-authored-by: Humberto Jimenez <humberto.jimenez@ni.com>
Co-authored-by: Ian Buckley <ian.buckley@gmail.com>
Co-authored-by: Jörg Hofrichter <joerg.hofrichter@ni.com>
Co-authored-by: Jon Kiser <jon.kiser@ni.com>
Co-authored-by: Josh Blum <josh@joshknows.com>
Co-authored-by: Jonathon Pendlum <jonathan.pendlum@ettus.com>
Co-authored-by: Martin Braun <martin.braun@ettus.com>
Co-authored-by: Matt Ettus <matt@ettus.com>
Co-authored-by: Michael West <michael.west@ettus.com>
Co-authored-by: Moritz Fischer <moritz.fischer@ettus.com>
Co-authored-by: Nick Foster <nick@ettus.com>
Co-authored-by: Nicolas Cuervo <nicolas.cuervo@ettus.com>
Co-authored-by: Paul Butler <paul.butler@ni.com>
Co-authored-by: Paul David <paul.david@ettus.com>
Co-authored-by: Ryan Marlow <ryan.marlow@ettus.com>
Co-authored-by: Sugandha Gupta <sugandha.gupta@ettus.com>
Co-authored-by: Sylvain Munaut <tnt@246tNt.com>
Co-authored-by: Trung Tran <trung.tran@ettus.com>
Co-authored-by: Vidush Vishwanath <vidush.vishwanath@ettus.com>
Co-authored-by: Wade Fife <wade.fife@ettus.com>

1 files changed, 126 insertions, 0 deletions

diff --git a/fpga/usrp3/lib/control/serial_to_settings.v b/fpga/usrp3/lib/control/serial_to_settings.v
new file mode 100644
index 000000000..180191fa5
--- /dev/null
+++ b/fpga/usrp3/lib/control/serial_to_settings.v
@@ -0,0 +1,126 @@
+//
+// Copyright 2014 Ettus Research LLC
+// Copyright 2018 Ettus Research, a National Instruments Company
+//
+// SPDX-License-Identifier: LGPL-3.0-or-later
+//
+
+module serial_to_settings
+  (
+   input clk,
+   input reset,
+   // Serial signals (async)
+   input scl,
+   input sda,
+   // Settngs bus out
+   output reg set_stb,
+   output reg [7:0] set_addr,
+   output reg [31:0] set_data,
+   // Debug
+   output [31:0] debug
+   );
+
+   reg [2:0] 	 state;
+   
+   localparam 	 SEARCH = 3'h0;
+   localparam 	 ADDRESS = 3'h1;
+   localparam 	 DATA = 3'h2;
+   localparam 	 STOP1 = 3'h3;
+   localparam 	 STOP2 = 3'h4;
+ 	 
+   reg 		 scl_pre_reg, scl_reg, scl_reg2;
+   reg 		 sda_pre_reg, sda_reg, sda_reg2;
+   reg [4:0] 	 counter;
+
+ 
+     always @(posedge clk) begin
+      scl_reg2 <= scl_reg;
+      scl_reg <= scl_pre_reg;
+      scl_pre_reg <= scl;
+      sda_reg2 <= sda_reg;
+      sda_reg <= sda_pre_reg;
+      sda_pre_reg <= sda;
+   end
+
+   
+   always @(posedge clk)
+     if (reset) begin
+	state <= SEARCH;
+	counter <= 0;
+	set_addr <= 0;
+	set_data <= 0;
+	set_stb <= 0;
+     end else begin
+	case(state)
+	  //
+	  // Search for I2C like start indication: SDA goes low whilst clock is high.
+	  //
+	  SEARCH: begin
+	     set_stb <= 0;
+	     // Look for START.
+	     if (scl_reg && scl_reg2 && !sda_reg && sda_reg2) begin
+		state <= ADDRESS;
+		counter <= 0;
+	     end
+	  end
+	  //
+	  // Count 8 Address bits.
+	  // Master changes SDA on falling edge of SCL, we sample on the rising edge.
+	  //
+	  ADDRESS: begin
+	     if (scl_reg && !scl_reg2) begin
+		set_addr[7:0] <= {set_addr[6:0],sda_reg};
+		if (counter == 7) begin
+		   state <= DATA;
+		   counter <= 0;
+		end else
+		  counter <= counter + 1;		  
+	    end
+	  end
+	  //
+	  // Count 32 data bits.
+	  // Master changes SDA on falling edge of SCL, we sample on the rising edge.
+	  //
+	  DATA: begin
+	     if (scl_reg && !scl_reg2) begin
+		set_data[31:0] <= {set_data[30:0],sda_reg};
+		if (counter == 31) begin
+		   state <= STOP1;
+		   counter <= 0;
+		end else
+		  counter <= counter + 1;		  
+	    end
+	  end
+	  //
+	  // Looks for rising SCL edge before STOP bit.
+	  //
+	  STOP1: begin
+	     if (scl_reg && !scl_reg2) begin
+		state <= STOP2;
+	     end
+	  end
+	  //
+	  // Looks for STOP bit
+	  //
+	  STOP2: begin
+	     if (scl_reg && scl_reg2 && sda_reg && !sda_reg2) begin
+		state <= SEARCH;
+		counter <= 0;
+		set_stb <= 1;
+	     end
+	  end
+	  
+	endcase // case(state)
+     end // else: !if(reset)
+
+   assign debug =
+		 {
+		  counter[4:0],
+		  state[2:0],
+		  scl_reg,
+		  sda_reg
+		  };
+   
+
+
+endmodule // serial_to_settings