Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

FPGA RS232 Communication

Status
Not open for further replies.
K

Kolnad

Newbie level 3
Newbie level 3
Joined
Feb 25, 2016
Messages
3
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Visit site
Activity points
24
Hello, I am doing some experiments on FPGA Spartan 6.
The experiment is, - Based on the input signal (named "trigger_to_tx"), uart has to transmit the string "Hello" to PC and one LED has to glow (named "tx_done) after the transmission. I have written the Verilog code for this experiment and attached below. For this code how to add input trigger signal and I am unable to see transmission completion in LED.

Code: 
module Top_module(
	input wire clk,   // System clock
   input wire rst,
   input wire trigger_tx,	
   output wire tx,	
	output [39:0]string_to_tx,
	output tx_done
                );

/// Data to Transmit ///
assign string_to_tx="Hello";

uart_tx_fsm fsm0(.clk(clk),
					.rst(rst),
					/*.trigger_tx(trigger_tx),*/
					.tx(tx),
					.string_to_tx(string_to_tx),
					.tx_complete(tx_complete)
					);

assign tx_done=(tx_complete)? 1:0;

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
module uart_tx_fsm(
    input wire clk,   //-- System clock
      input wire rst,  //-- Reset (active low)
      output wire tx,    //-- Serial data output
		input [39:0]string_to_tx,
		output tx_complete
                  );

     //Connecting wires
wire ready;
reg start = 0;
reg [7:0] tx_data;

reg tx_done;
parameter BAUDRATE = 1041;

uart_tx TX0 (
    .clk(clk),
    .rst(~rst),
    .tx_data(tx_data),
    .start(start),
    .tx(tx),
    .ready(ready)
);

// Multiplexer with the 8-character string to transmit
always @*
  case (char_count)
    3'd0: tx_data <= string_to_tx[39:32];
    3'd1: tx_data <= string_to_tx[31:24];
    3'd2: tx_data <= string_to_tx[23:16];
    3'd3: tx_data <= string_to_tx[15:8];
    3'd4: tx_data <= string_to_tx[7:0];
	 3'd5: tx_data <= 8'hd;   // Enter
	 default: tx_data <= 8'h20;  //Space
  endcase

// Characters counter
// It only counts when the cena control signal is enabled
reg [2:0] char_count;
reg cena;                // Counter enable

always @(posedge clk)
  if (rst)
    char_count = 0;
  else if (cena)
    char_count = char_count + 1;

                // CONTROLLER

localparam INI = 0;
localparam TXCAR = 1;
localparam NEXTCAR = 2;
localparam STOP = 3;

  // fsm state
reg [1:0] state;
reg [1:0] next_state;

   // Transition between states
always @(posedge clk) begin
  if (rst)
    state <= INI;
  else
    state <= next_state;
end

        // Control signal generation and next states
always @(*) 
  begin
  next_state = state;
  start = 0;
  cena = 0;

  case (state)
     // Initial state. Start the trasmission
    INI: begin
      start = 1;
      next_state = TXCAR;
    end

    // Wait until one car is transmitted
    TXCAR: begin
      if (ready)
        next_state = NEXTCAR;
    end

    // Increment the character counter
    // Finish when it is the last character
    NEXTCAR: begin
      cena = 1;
      if (char_count == 3'd5)
		  begin
        next_state = STOP;
		  end
      else
        next_state = INI;
    end

  endcase
end

assign tx_complete= (char_count==3'd5)? 1:0;

endmodule
 
Last edited by a moderator:

start with debugging your state machine, it doesn't increment to the next character, and it's just the beginning of a UART transmitter.

If you've done that, you will probably know by then how to inject your input trigger.
 
  • Like
Reactions: Kolnad

    K

    Kolnad

    Points: 2
    Helpful Answer Positive Rating
lucbra said:
start with debugging your state machine, it doesn't increment to the next character, and it's just the beginning of a UART transmitter.
Click to expand...

Here I corrected the code and it is transmitting string "Hello" without any triggering signal.

Code: 
module Top_one(
	input wire clk,   //-- System clock
   input wire rst,	
   output wire tx,	//-- Serial data output
	output [39:0]string_to_tx
                );

/// Data to Transmit ///
assign string_to_tx="Hello";

uart_tx_fsm fsm0(.clk(clk),
					.rst(rst),
					.tx(tx),
					.string_to_tx(string_to_tx)
					);

endmodule

///////////////////////////////////////////////////////////////////////////////////////////

module uart_tx_fsm(
input wire clk,   //-- System clock
      input wire rst,  //-- Reset (active low)
      output wire tx,    //-- Serial data output
		input [39:0]string_to_tx
                  );

     //Connecting wires
wire ready;
reg start = 0;
reg [7:0] tx_data;

reg tx_done;
parameter BAUDRATE = 1041;

uart_tx TX0 (
    .clk(clk),
    .rst(~rst),
    .tx_data(tx_data),
    .start(start),
    .tx(tx),
    .ready(ready)
);

// Multiplexer with the 8-character string to transmit
always @*
  case (char_count)
    3'd0: tx_data <= string_to_tx[39:32];
    3'd1: tx_data <= string_to_tx[31:24];
    3'd2: tx_data <= string_to_tx[23:16];
    3'd3: tx_data <= string_to_tx[15:8];
    3'd4: tx_data <= string_to_tx[7:0];
	 3'd5: tx_data <= 8'hd;   // Enter
	 default: tx_data <= 8'h20;  //Space
  endcase

// Characters counter
// It only counts when the cena control signal is enabled
reg [2:0] char_count;
reg cena;                // Counter enable

always @(posedge clk)
  if (rst)
    char_count = 0;
  else if (cena)
    char_count = char_count + 1;

                // CONTROLLER

localparam INI = 0;
localparam TXCAR = 1;
localparam NEXTCAR = 2;
localparam STOP = 3;

  // fsm state
reg [1:0] state;
reg [1:0] next_state;

   // Transition between states
always @(posedge clk) begin
  if (rst)
    state <= INI;
  else
    state <= next_state;
end

        // Control signal generation and next states
always @(*) 
  begin
  next_state = state;
  start = 0;
  cena = 0;

  case (state)
     // Initial state. Start the trasmission
    INI: begin
      start = 1;
      next_state = TXCAR;
    end

    // Wait until one car is transmitted
    TXCAR: begin
      if (ready)
        next_state = NEXTCAR;
    end

    // Increment the character counter
    // Finish when it is the last character
    NEXTCAR: begin
      cena = 1;
      if (char_count == 3'd5)
		  begin
        next_state = STOP;
		  end
      else
        next_state = INI;
    end

  endcase
end

endmodule
 

There's apparently no change expect omitting the trigger and complete signal. So if it outputs a string now (I guess once after reset), it should have done before.

Anyway, what's the problem now?
 

In my experiment, I wanted to include one output signal/flag It should set when transmission completes. Because, I am instantiating one more separate module based on this completion signal. In my program, where can i add that output completion signal?
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top