spi: created simple spi core (sr based)

1 files changed, 195 insertions, 0 deletions

diff --git a/usrp2/control_lib/simple_spi_core.v b/usrp2/control_lib/simple_spi_core.v
new file mode 100644
index 000000000..4772180a7
--- /dev/null
+++ b/usrp2/control_lib/simple_spi_core.v
@@ -0,0 +1,195 @@
+//
+// Copyright 2012 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 SPI core, the simplest, yet complete spi core I can think of
+
+// Settings register controlled.
+// 2 settings regs, control and data
+// 1 32-bit readback and status signal
+
+// Settings reg map:
+//
+// BASE+0 divider setting
+// bits [15:0] spi clock divider
+//
+// BASE+1 configuration input
+// bits [23:0] slave select, bit0 = slave0 enabled
+// bits [29:24] num bits (1 through 32)
+// bit [30] data input edge = in data bit latched on rising edge of clock
+// bit [31] data output edge = out data bit latched on rising edge of clock
+//
+// BASE+2 input data
+// Writing this register begins a spi transaction.
+// Bits are latched out from bit 0.
+// Therefore, load this register in reverse.
+//
+// Readback
+// Bits are latched into bit 0.
+// Therefore, data will be in-order.
+
+module simple_spi_core
+    #(
+        //settings register base address
+        parameter BASE = 0,
+
+        //width of serial enables (up to 24 is possible)
+        parameter WIDTH = 8,
+
+        //idle state of the spi clock
+        parameter CLK_IDLE = 1,
+
+        //idle state of the serial enables
+        parameter SEN_IDLE = 24'hffffff
+    )
+    (
+        //clock and synchronous reset
+        input clock, input reset,
+
+        //32-bit settings bus inputs
+        input set_stb, input [7:0] set_addr, input [31:0] set_data,
+
+        //32-bit data readback
+        output [31:0] readback,
+        
+        //done is high for one cycle after a spi transaction
+        output done,
+
+        //spi interface, slave selects, clock, data in, data out
+        output [WIDTH-1:0] sen,
+        output sclk,
+        output mosi,
+        input miso,
+
+        //optional debug output
+        output [31:0] debug
+    );
+
+    wire [15:0] sclk_divider;
+    setting_reg #(.my_addr(BASE+0),.width(16)) divider_sr(
+        .clk(clock),.rst(reset),.strobe(set_stb),.addr(set_addr),.in(set_data),
+        .out(sclk_divider),.changed());
+
+    wire [23:0] slave_select;
+    wire [5:0] num_bits;
+    wire datain_edge, dataout_edge;
+    setting_reg #(.my_addr(BASE+1),.width(32)) config_sr(
+        .clk(clock),.rst(reset),.strobe(set_stb),.addr(set_addr),.in(set_data),
+        .out({dataout_edge, datain_edge, num_bits, slave_select}),.changed());
+
+    wire [31:0] mosi_data;
+    wire trigger_spi;
+    setting_reg #(.my_addr(BASE+2),.width(32)) data_sr(
+        .clk(clock),.rst(reset),.strobe(set_stb),.addr(set_addr),.in(set_data),
+        .out(mosi_data),.changed(trigger_spi));
+
+    localparam WAIT_TRIG = 0;
+    localparam PRE_IDLE = 1;
+    localparam CLK_REG = 2;
+    localparam CLK_INV = 3;
+    localparam POST_IDLE = 4;
+    localparam TRANS_DONE = 5;
+
+    reg [2:0] state;
+
+    assign done = (state == TRANS_DONE);
+
+    //serial clock either idles or is in one of two clock states
+    assign sclk = (state == CLK_INV)? ~CLK_IDLE : (state == CLK_REG)? CLK_IDLE : CLK_IDLE;
+
+    //serial enables either idle or enabled based on state
+    wire [23:0] sen24 = (state == WAIT_TRIG || state == TRANS_DONE)? SEN_IDLE : (SEN_IDLE ^ slave_select);
+    assign sen = sen24[WIDTH-1:0];
+
+    //data output shift register
+    reg [31:0] dataout_reg;
+    wire [31:0] dataout_next = {0, dataout_reg[31:1]};
+    assign mosi = (state == CLK_INV || state == CLK_REG)? dataout_reg[0] : 0;
+
+    //data input shift register
+    reg [31:0] datain_reg;
+    wire [31:0] datain_next = {datain_reg[30:0], miso};
+    assign readback = datain_reg;
+
+    //counter for spi clock
+    reg [15:0] sclk_counter;
+    wire sclk_counter_done = (sclk_counter == sclk_divider);
+    wire [15:0] sclk_counter_next = (sclk_counter_done)? 0 : sclk_counter + 1;
+
+    //counter for latching bits miso/mosi
+    reg [6:0] bit_counter;
+    wire [6:0] bit_counter_next = bit_counter + 1;
+    wire bit_counter_done = (bit_counter_next == num_bits);
+
+    always @(posedge clock) begin
+        if (reset) begin
+            state <= WAIT_TRIG;
+        end
+        else begin
+            case (state)
+
+            WAIT_TRIG: begin
+                if (trigger_spi) state <= PRE_IDLE;
+                sclk_counter <= 0;
+            end
+
+            PRE_IDLE: begin
+                if (sclk_counter_done) state <= CLK_REG;
+                sclk_counter <= sclk_counter_next;
+                dataout_reg <= mosi_data;
+                bit_counter <= 0;
+            end
+
+            CLK_REG: begin
+                if (sclk_counter_done) begin
+                    state <= CLK_INV;
+                    if (~datain_edge)  datain_reg  <= datain_next;
+                    if (~dataout_edge) dataout_reg <= dataout_next;
+                end
+                sclk_counter <= sclk_counter_next;
+            end
+
+            CLK_INV: begin
+                if (sclk_counter_done) begin
+                    state <= (bit_counter_done)? POST_IDLE : CLK_REG;
+                    bit_counter <= bit_counter_next;
+                    if (datain_edge)  datain_reg  <= datain_next;
+                    if (dataout_edge) dataout_reg <= dataout_next;
+                end
+                sclk_counter <= sclk_counter_next;
+            end
+
+            POST_IDLE: begin
+                if (sclk_counter_done) state <= TRANS_DONE;
+                sclk_counter <= sclk_counter_next;
+            end
+
+            default: state <= WAIT_TRIG;
+
+            endcase //state
+        end
+    end
+
+    assign debug = {
+        trigger_spi, state, //4
+        sclk, mosi, miso, done, //4
+        sen[7:0], //8
+        1'b0, bit_counter[6:0], //8
+        sclk_counter_done, bit_counter_done, //2
+        sclk_counter[5:0] //6
+    };
+
+endmodule //simple_spi_core