Questions about SPIADC on Papilio Pro LX9


Recommended Posts

Hi all, I'm trying to work with SPIADC on Papilio Pro LX9 and I have some questions:

1. What type of ADC device is the analogue example sketch written for? In SPIADC example sketch, the WISHBONESLOT(6) was used but it was not found in schematics of Papilio Pro LX9 board.

2. If we use slot1 on Vanilla, how do we enable MOSI etc. signals to route them to a Wing pin?


Thanks a million.

Link to comment
Share on other sites



All of the SPI ADC examples are for the Analog Grove Wing.


Please see this page for an example of shifting a pin with the Vanilla variant.


For tutorials about the Schematic library look at tutorials here:

Link to comment
Share on other sites

I use the following code to process ADC input from a Retrocade mega wing. That board has 2x8bit ADC chips communicating over SPI.


`timescale 1ns / 1ps
// Engineer:       Stephen Davies
// Create Date:    21:05:48 10 Jan 2013
// Design Name:    
// Module Name:    ADC
// Project Name:   MiniMoog sim
// Target Devices: Spartan 6
// Tool versions:  ISE 14.4
// Description:    State machine logic for polling a TI ADC088S102 ADC chip.
//                 Logic operates in a loop, polling the current port value in a
//                 single 'frame'. Each input port (of 8) is sampled in its own
//                 frame, delimited by CS, so that synchronisation is maintained.
//                 A future implementation could make the frames larger, querying all
//                 8 ports in a single frame. This would improve throughput. Maximum
//                 throughput would sample each individual port @125k samples/s. Per port
//                 framing reduces this a little but not enough to worry about given
//                 that the main function for the analog pins is to attach pots & switches.
// Dependencies:
// Revision:       0.01
// Revision 0.01 - File Created
// Additional Comments:

module ADC
        parameter ADC_WIDTH=8            // ADC sample size in bits
   input clk,                        // 16 MHz clk (max for ADC088S102)
   input reset,                    // active high

   output sck,                        // SPI clock (16MHz max for ADC088S102)
   output reg cs_n,                // ADC chip select, active low
   input  din,                        // data stream from ADC chip, sampled on rising edge of SCK
   output reg dout,                // data stream to ADC, ADC chip samples on rising edge of SCK
    input [2:0] addr,                // register read address
    output [ADC_WIDTH-1:0] q    // register output value

    // State machine states
   localparam RESYNC = 1'b0;    // ADC chip select (CS) taken high
   localparam SAMPLE = 1'b1;    // ADC chip select (CS) taken low, analog data being sampled

    // Variables
   reg  [6:0]  count;            // 7 bit counter, low order 4 bits count 16 SCK pulses per frame.
                                        // high order 3 bits indicate current port
    wire [2:0]  currentPort;    // port we are receiving dataIn for
   reg  [4:0]  dataOut;            // Output shift register, contains next port address and two 0 bits. Not all 16 bits are required as unused bits default to 0.
    reg  [15:0] dataIn;            // Input shift register, contains current anaolg sample plus padding
    wire [2:0]  nextPort;        // next analog port to be read, sent as part of current dataOut frame
    wire        endFrameTick;    // indicates end of frame has been reached, drives FSM through RESYNC state

   reg [ADC_WIDTH-1:0] adcReg [7:0];

    reg state = RESYNC;                            // FSM state (at initial state)
    assign endFrameTick = &count[3:0];        // at end EOF when count == 4'b1111
    assign currentPort = count[6:4];            // values 0-7
    assign nextPort = currentPort + 3'd1;
    assign q = adcReg[addr];
    // FSM
   always@(posedge clk, posedge reset)
      if (reset) begin                            // system reset
         state <= RESYNC;
            count <= 7'b0;
            cs_n  <= 1'b1;
         (* PARALLEL_CASE, FULL_CASE *) case (state)
            RESYNC : begin                        // immediately moves to SAMPLE state after resetting key values
               state <= SAMPLE;
                    count <= { count[6:4], 4'b0 };    // preserves nextPort value
               cs_n  <= 1'b0;
            SAMPLE : begin
               if (endFrameTick) begin                // when 15 SCK cycles have occurred, RESYNC for next analog port
                  state <= RESYNC;
                        count <= count + 7'd1;
                        cs_n <= 1'b1;
               else begin                                // keep on clocking...
                  state <= state;
                        count <= count + 7'd1;
                        cs_n <= 1'b0;
            default: begin                                // Fault Recovery
               state <= RESYNC;
                    count <= 7'b0;
                    cs_n  <= 1'b1;
    // DOUT shift register, selects next port to sample
    // 5 bits long because first 3 bits are zero, next 3 are port and next 10 are zero.
    always @(negedge clk, posedge reset)
      if (reset) begin
         dataOut <= 5'b0;
         dout    <= 1'b0;
      else if (cs_n) begin        // load register at start of frame
         dataOut <= { nextPort[0], nextPort[1], nextPort[2], 2'b0 };
         dout    <= 1'b0;
      else if (!cs_n) begin    // shift next bit
         dataOut <= { 1'b0, dataOut[4:1] };
         dout    <= dataOut[0];

    // DIN shift register
   always @(posedge clk)
      if (!cs_n)
         dataIn <= { dataIn[14:0], din };
            adcReg[currentPort] <= dataIn[11:4];
    // Spartan 6 requires special handling for sending clk16 on SCK pin. (not a 'special' clock output pin apparently)
    ODDR2 ODDR2_inst (.Q(sck), .C0(clk), .C1(!clk), .CE(1'b1), .D0(1'b1), .D1(1'b0), .R(1'b0), .S(1'b0));

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.