pluto_hdl_adi/projects/daq1/common/daq1_spi.v

// ***************************************************************************
// ***************************************************************************
// Copyright 2014 - 2017 (c) Analog Devices, Inc. All rights reserved.
//
// Each core or library found in this collection may have its own licensing terms. 
// The user should keep this in in mind while exploring these cores. 
//
// Redistribution and use in source and binary forms,
// with or without modification of this file, are permitted under the terms of either
//  (at the option of the user):
//
//   1. The GNU General Public License version 2 as published by the
//      Free Software Foundation, which can be found in the top level directory, or at:
// https://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html
//
// OR
//
//   2.  An ADI specific BSD license as noted in the top level directory, or on-line at:
// https://github.com/analogdevicesinc/hdl/blob/dev/LICENSE
//
// ***************************************************************************
// ***************************************************************************

`timescale 1ns/100ps

module daq1_spi (

  input                   spi_csn,
  input                   spi_clk,
  input                   spi_mosi,
  output                  spi_miso,

  inout                   spi_sdio);

  // device address

  localparam  [ 7:0]  SPI_SEL_AD9684  = 8'h80;
  localparam  [ 7:0]  SPI_SEL_AD9122  = 8'h81;
  localparam  [ 7:0]  SPI_SEL_AD9523  = 8'h82;
  localparam  [ 7:0]  SPI_SEL_CPLD    = 8'h83;

  // internal registers

  reg     [ 5:0]  spi_count = 6'b0;
  reg             spi_rd_wr_n = 1'b0;
  reg             spi_enable = 1'b0;
  reg     [ 7:0]  spi_device_addr = 8'b0;

  // internal signals

  wire            spi_enable_s;

  // check on rising edge and change on falling edge

  assign spi_enable_s = spi_enable & ~spi_csn;

  always @(posedge spi_clk or posedge spi_csn) begin
    if (spi_csn == 1'b1) begin
      spi_count <= 6'b0000000;
      spi_rd_wr_n <= 1'b0;
      spi_device_addr <= 8'b00000000;
    end else begin
      spi_count <= (spi_count < 6'h3f) ? spi_count + 1'b1 : spi_count;
      if (spi_count <= 6'd7) begin
        spi_device_addr <= {spi_device_addr[6:0], spi_mosi};
      end
      if (spi_count == 6'd8) begin
        spi_rd_wr_n <= spi_mosi;
      end
    end
  end

  always @(negedge spi_clk or posedge spi_csn) begin
    if (spi_csn == 1'b1) begin
      spi_enable <= 1'b0;
    end else begin
      if (((spi_device_addr == SPI_SEL_AD9684) && (spi_count == 6'd24)) ||
          ((spi_device_addr == SPI_SEL_AD9122) && (spi_count == 6'd16)) ||
          ((spi_device_addr == SPI_SEL_AD9523) && (spi_count == 6'd24)) ||
          ((spi_device_addr == SPI_SEL_CPLD)   && (spi_count == 6'd16))) begin
        spi_enable <= spi_rd_wr_n;
      end
    end
  end

  // io logic

  assign spi_miso = spi_sdio;
  assign spi_sdio = (spi_enable_s == 1'b1) ? 1'bz : spi_mosi;

endmodule

// ***************************************************************************
// ***************************************************************************