Ok, after making some posts on a c++ forum i've gained some insight. I'm trying to hardcode the data rate to 9600bps, and am using the following code:
module test5(input CLOCK_50,
output [2:0] LEDR,
//output LCD_ON,
//output LCD_BLON,
//output LCD_RW,
//output LCD_EN,
//output LCD_RS,
//output [7:0] LCD_DATA,
output UART_TXD,
//input UART_RXD
input [0:0] SW
);
reg [13:0] waiter = 13'b0000000000000; //counter to reduce clock rate
reg [3:0] state = 4'b0000; //current state. 0 = start bit, 1-8 = data bits, 9 = stop bit, other = ended
reg data = 1'b1; //start high = idle state
reg clk_new = 0; //changes the state of an led every time a bit is sent
assign LEDR[0] = data; //led outputs current data bit
assign LEDR[1] = SW; //led outputs status of a switch
assign LEDR[2] = clk_new; //led shows when new bit is sent
assign UART_TXD = data; //assert the transmit wire to the data bit
always @(posedge CLOCK_50) //every clock tick
begin
if (waiter == 13'b1010101010101) //9600 times a second (aprox)
begin
clk_new = !clk_new; //change clock led
waiter = 27'b000000000000000000000000000; //reset counter
case (state) //switch on the current state
4'h0:begin //in state 0
if (SW) //check to see if switch is high, if so start, else do nothing
begin
data = 0; //start bit
state = state + 1'b1;
end
end
4'h1:begin //data bits = 00111001b = 57d (9 in ascii)
data = 1'b0;
state = state + 1'b1;
end
4'h2:begin
data = 1'b0;
state = state + 1'b1;
end
4'h3:begin
data = 1'b1;
state = state + 1'b1;
end
4'h4:begin
data = 1'b1;
state = state + 1'b1;
end
4'h5:begin
data = 1'b1;
state = state + 1'b1;
end
4'h6:begin
data = 1'b0;
state = state + 1'b1;
end
4'h7:begin
data = 1'b0;
state = state + 1'b1;
end
4'h8:begin
data = 1'b1;
state = state + 1'b1;
end
4'h9:begin //stop bit
data = 1'b1;
state = state + 1'b1;
end
default:begin
data = 1'b1; //idle bit
end
endcase
end //end if (waiter == ...)
waiter = waiter + 1'b1; //inc waiter
end //end always @...
endmodule
transmits the ascii character '9' at 9600bps 1 start bit, 1 stop bit, 0 parity bits.
I set up hyperterminal to those settings + flow control = none. And connected to com1. I run my verilog code and switch the switch to high, but nothing appears on the terminal.
I set the data rate on the board to about 1/2 bit a second, so i could watch the leds, and they outputted correctly, so i'm definetly setting data to the correct values.
My code looks correct to me, so i'm guessing i am formatting the frame incorrectly. Any help would be really apreciated.
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