FPGA - PC communication

[Altera_Forum]

Hey all, I am trying to get my DE2-115 board and my pc to communicate, but I have no idea where to even start. So far my FPGA training begins and ends with the 10 labs that came with the DE board, plus a few projects I did for fun. So, I have two questions: 

 1. Given that I have no knowledge of communication protocols and such, would it be easiest for me to learn and implement USB, Ethernet, or RS232? 2. Based on your answer to the first, can you please suggest some learning resources I could consult?  Much Appreciated

[Altera_Forum]

RS232 is by far the easiest to implement. Many products still include RS232 as it is easy and cheap to implement on the FPGA and works with little debugging. Ethernet and USB are both massively complex. You cannot find USB or Ethernet cores for free. 

 There are plenty of RS232 examples if you use google. Here is the first: http://www.fpga4fun.com/serialinterface.html

[Altera_Forum]

Very few of the current PCs have an RS-232 port, but USB to RS-232 adapters are available.

[Altera_Forum]

Thanks much! RS232 it is:).

[Altera_Forum]

Hey just try my code - I have programmed the RS232 successfully today: 

 //******************************************************* //****** PAVLE DUKANOVIC ******* //****** www.dukelanovic.com ******* //****** dukelanovic@yahoo.de ******* //*******************************************************   // Serial port demo program // http://www.techques.com/question/4-13718/implement-serial-port-on-fpga-(verilog)  // Assumptions: 50Mhz clock rate   module serial(input clk,input key_in, output ser, input rxd);     // Start signal tells it to start sending bits   reg[24:0]count; reg [3:0] ones; reg [3:0] tens; //The bits of data to send reg [7:0] data; reg sec; reg [14:0] clockdiv; reg [14:0] clockdivrx; // Output register to pin assign ser = outbit;   // Count from 0..5207 then reset back to zero (9600 Baud for TX) always @(posedge clk)  begin  if (clockdiv == 5207)   clockdiv <= 0;  else  clockdiv <= clockdiv + 1; end   // Count from 0..5207 then reset back to zero (9600 Baud for TX) always @(posedge clk)  begin  if (clockdivrx == 1302)   clockdivrx <= 0;  else  clockdivrx <= clockdivrx + 1; end     // The serclock is a short pulse each time we are reset wire serclock = (clockdiv == 0); wire start = (clockdiv == 0); wire serclockrx = (clockdivrx == 0);   ///////////////////////////////////////////////////////////////////////////// // Serial port state machine // Only start the state machine when "start" is set. Only advance to the // next state when serclock is set.   reg [3:0] state;   always @(posedge clk) begin  case (state)  4'b0000: if (start) state <= 4'b0001;  4'b0001: if (serclock) state <= 4'b0010; // Start bit  4'b0010: if (serclock) state <= 4'b0011; // Bit 0  4'b0011: if (serclock) state <= 4'b0100; // Bit 1  4'b0100: if (serclock) state <= 4'b0101; // Bit 2  4'b0101: if (serclock) state <= 4'b0110; // Bit 3  4'b0110: if (serclock) state <= 4'b0111; // Bit 4  4'b0111: if (serclock) state <= 4'b1000; // Bit 5  4'b1000: if (serclock) state <= 4'b1001; // Bit 6  4'b1001: if (serclock) state <= 4'b1010; // Bit 7  4'b1010: if (serclock) state <= 4'b0000; // Stop bit  default: state <= 4'b0000; // Undefined, skip to stop  endcase end   /////////////////////////////////////////////////////////////////////////////// // Serial port data // Ensure that the serial port has the correct data on it in each state   reg outbit;   always @(posedge clk) begin  case (state)  4'b0000: outbit <= 1; // idle  4'b0001: outbit <= 0; // Start bit  4'b0010: outbit <= data[0]; // Bit 0  4'b0011: outbit <= data[1]; // Bit 1  4'b0100: outbit <= data[2]; // Bit 2  4'b0101: outbit <= data[3]; // Bit 3  4'b0110: outbit <= data[4]; // Bit 4  4'b0111: outbit <= data[5]; // Bit 5  4'b1000: outbit <= data[6]; // Bit 6  4'b1001: outbit <= data[7]; // Bit 7  4'b1010: outbit <= 0; // Stop bit  default: outbit <= 1;df // Bad state output idle  endcase end   reg [7:0] charstate;   reg [5:0] rxstate;   always @(posedge clk) begin  case (rxstate)  6'b000000: if (!rxd) rxstate <= 4'b000001;  6'b000001: if (serclockrx) rxstate <= 6'b000010;   6'b000010: if (serclockrx) rxstate <= 6'b000011;   6'b000011: if (serclockrx) rxstate <= 6'b000100;     6'b000100: if (serclockrx) rxstate <= 6'b000101;   6'b000101: if (serclockrx) rxstate <= 6'b000110;   6'b000110: if (serclockrx) begin rxstate <= 6'b000111; data[0] <= rxd; end // The sixth tact LSB reg [7:0] data;  6'b000111: if (serclockrx) rxstate <= 6'b001000;     6'b001000: if (serclockrx) rxstate <= 6'b001001;   6'b001001: if (serclockrx) rxstate <= 6'b001010;   6'b001010: if (serclockrx) begin rxstate <= 6'b001011; data[1] <= rxd; end // The 10'th tact   6'b001011: if (serclockrx) rxstate <= 6'b001100;    6'b001100: if (serclockrx) rxstate <= 6'b001101;   6'b001101: if (serclockrx) rxstate <= 6'b001110;   6'b001110: if (serclockrx) begin rxstate <= 6'b001111; data[2] <= rxd; end // The 14'th tact   6'b001111: if (serclockrx) rxstate <= 6'b010000;     6'b010000: if (serclockrx) rxstate <= 6'b010001;   6'b010001: if (serclockrx) rxstate <= 6'b010010;   6'b010010: if (serclockrx) begin rxstate <= 6'b010011; data[3] <= rxd; end // The 18'th tact   6'b010011: if (serclockrx) rxstate <= 6'b010100;     6'b010100: if (serclockrx) rxstate <= 6'b010101;   6'b010101: if (serclockrx) rxstate <= 6'b010110;   6'b010110: if (serclockrx) begin rxstate <= 6'b010111; data[4] <= rxd; end // The 22'nd tact   6'b010111: if (serclockrx) rxstate <= 6'b011000;     6'b011000: if (serclockrx) rxstate <= 6'b011001;   6'b011001: if (serclockrx) rxstate <= 6'b011010;   6'b011010: if (serclockrx) begin rxstate <= 6'b011011; data[5] <= rxd; end // The 26'th tact   6'b011011: if (serclockrx) rxstate <= 6'b011100;     6'b011100: if (serclockrx) rxstate <= 6'b011101;   6'b011101: if (serclockrx) rxstate <= 6'b011110;   6'b011110: if (serclockrx) begin rxstate <= 6'b011111; data[6] <= rxd; end // The 30'th tact   6'b011111: if (serclockrx) rxstate <= 6'b100000;     6'b100000: if (serclockrx) rxstate <= 6'b100001;   6'b100001: if (serclockrx) rxstate <= 6'b100010;   6'b100010: if (serclockrx) begin rxstate <= 6'b100011; data[7] <= rxd; end // The 34'th tact   6'b100011: if (serclockrx) rxstate <= 6'b100100;    6'b100100: if (serclockrx) rxstate <= 6'b100101;   6'b100101: if (serclockrx) rxstate <= 6'b100110;     default: rxstate <= 6'b000000;   endcase end   endmodule  There only one problem remained in the whole story - as I have been pressing a key in Putty.exe the module always was sending characters. So is here somebody who could give me a hint how I could program the whole story so that the module sends back only  one character?

[Altera_Forum]

--- Quote Start ---  Hey just try my code - I have programmed the RS232 successfully today:  //******************************************************* //****** PAVLE DUKANOVIC ******* //****** www.dukelanovic.com (http://www.dukelanovic.com) ******* //****** dukelanovic@yahoo.de ******* //*******************************************************   // Serial port demo program // http://www.techques.com/question/4-13718/implement-serial-port-on-fpga-(verilog)  // Assumptions: 50Mhz clock rate   module serial(input clk,input key_in, output ser, input rxd);     // Start signal tells it to start sending bits   reg[24:0]count; reg [3:0] ones; reg [3:0] tens; //The bits of data to send reg [7:0] data; reg sec; reg [14:0] clockdiv; reg [14:0] clockdivrx; // Output register to pin assign ser = outbit;   // Count from 0..5207 then reset back to zero (9600 Baud for TX) always @(posedge clk)  begin  if (clockdiv == 5207)   clockdiv <= 0;  else  clockdiv <= clockdiv + 1; end   // Count from 0..5207 then reset back to zero (9600 Baud for TX) always @(posedge clk)  begin  if (clockdivrx == 1302)   clockdivrx <= 0;  else  clockdivrx <= clockdivrx + 1; end     // The serclock is a short pulse each time we are reset wire serclock = (clockdiv == 0); wire start = (clockdiv == 0); wire serclockrx = (clockdivrx == 0);   ///////////////////////////////////////////////////////////////////////////// // Serial port state machine // Only start the state machine when "start" is set. Only advance to the // next state when serclock is set.   reg [3:0] state;   always @(posedge clk) begin  case (state)  4'b0000: if (start) state <= 4'b0001;  4'b0001: if (serclock) state <= 4'b0010; // Start bit  4'b0010: if (serclock) state <= 4'b0011; // Bit 0  4'b0011: if (serclock) state <= 4'b0100; // Bit 1  4'b0100: if (serclock) state <= 4'b0101; // Bit 2  4'b0101: if (serclock) state <= 4'b0110; // Bit 3  4'b0110: if (serclock) state <= 4'b0111; // Bit 4  4'b0111: if (serclock) state <= 4'b1000; // Bit 5  4'b1000: if (serclock) state <= 4'b1001; // Bit 6  4'b1001: if (serclock) state <= 4'b1010; // Bit 7  4'b1010: if (serclock) state <= 4'b0000; // Stop bit  default: state <= 4'b0000; // Undefined, skip to stop  endcase end   /////////////////////////////////////////////////////////////////////////////// // Serial port data // Ensure that the serial port has the correct data on it in each state   reg outbit;   always @(posedge clk) begin  case (state)  4'b0000: outbit <= 1; // idle  4'b0001: outbit <= 0; // Start bit  4'b0010: outbit <= data[0]; // Bit 0  4'b0011: outbit <= data[1]; // Bit 1  4'b0100: outbit <= data[2]; // Bit 2  4'b0101: outbit <= data[3]; // Bit 3  4'b0110: outbit <= data[4]; // Bit 4  4'b0111: outbit <= data[5]; // Bit 5  4'b1000: outbit <= data[6]; // Bit 6  4'b1001: outbit <= data[7]; // Bit 7  4'b1010: outbit <= 0; // Stop bit  default: outbit <= 1;df // Bad state output idle  endcase end   reg [7:0] charstate;   reg [5:0] rxstate;   always @(posedge clk) begin  case (rxstate)  6'b000000: if (!rxd) rxstate <= 4'b000001;  6'b000001: if (serclockrx) rxstate <= 6'b000010;   6'b000010: if (serclockrx) rxstate <= 6'b000011;   6'b000011: if (serclockrx) rxstate <= 6'b000100;     6'b000100: if (serclockrx) rxstate <= 6'b000101;   6'b000101: if (serclockrx) rxstate <= 6'b000110;   6'b000110: if (serclockrx) begin rxstate <= 6'b000111; data[0] <= rxd; end // The sixth tact LSB reg [7:0] data;  6'b000111: if (serclockrx) rxstate <= 6'b001000;     6'b001000: if (serclockrx) rxstate <= 6'b001001;   6'b001001: if (serclockrx) rxstate <= 6'b001010;   6'b001010: if (serclockrx) begin rxstate <= 6'b001011; data[1] <= rxd; end // The 10'th tact   6'b001011: if (serclockrx) rxstate <= 6'b001100;    6'b001100: if (serclockrx) rxstate <= 6'b001101;   6'b001101: if (serclockrx) rxstate <= 6'b001110;   6'b001110: if (serclockrx) begin rxstate <= 6'b001111; data[2] <= rxd; end // The 14'th tact   6'b001111: if (serclockrx) rxstate <= 6'b010000;     6'b010000: if (serclockrx) rxstate <= 6'b010001;   6'b010001: if (serclockrx) rxstate <= 6'b010010;   6'b010010: if (serclockrx) begin rxstate <= 6'b010011; data[3] <= rxd; end // The 18'th tact   6'b010011: if (serclockrx) rxstate <= 6'b010100;     6'b010100: if (serclockrx) rxstate <= 6'b010101;   6'b010101: if (serclockrx) rxstate <= 6'b010110;   6'b010110: if (serclockrx) begin rxstate <= 6'b010111; data[4] <= rxd; end // The 22'nd tact   6'b010111: if (serclockrx) rxstate <= 6'b011000;     6'b011000: if (serclockrx) rxstate <= 6'b011001;   6'b011001: if (serclockrx) rxstate <= 6'b011010;   6'b011010: if (serclockrx) begin rxstate <= 6'b011011; data[5] <= rxd; end // The 26'th tact   6'b011011: if (serclockrx) rxstate <= 6'b011100;     6'b011100: if (serclockrx) rxstate <= 6'b011101;   6'b011101: if (serclockrx) rxstate <= 6'b011110;   6'b011110: if (serclockrx) begin rxstate <= 6'b011111; data[6] <= rxd; end // The 30'th tact   6'b011111: if (serclockrx) rxstate <= 6'b100000;     6'b100000: if (serclockrx) rxstate <= 6'b100001;   6'b100001: if (serclockrx) rxstate <= 6'b100010;   6'b100010: if (serclockrx) begin rxstate <= 6'b100011; data[7] <= rxd; end // The 34'th tact   6'b100011: if (serclockrx) rxstate <= 6'b100100;    6'b100100: if (serclockrx) rxstate <= 6'b100101;   6'b100101: if (serclockrx) rxstate <= 6'b100110;     default: rxstate <= 6'b000000;   endcase end   endmodule  There only one problem remained in the whole story - as I have been pressing a key in Putty.exe the module always was sending characters. So is here somebody who could give me a hint how I could program the whole story so that the module sends back only  one character?  --- Quote End ---    Your stop bit is 0. Needs to be 1.