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Found 2 results

  1. Hi,guys, I'm new and I have some problems in uart communication with PC(windows). I built UART RX (receiving) hardware. 8 LEDs will be used to show the binary value of the ASCII character. When the key strobe on the keyboard (from the computer) is pressed, the 8 bits will transmit from the keyboard to FPGA through USB-UART port on arty-7-35T board. However, when I send something to board through TERATERM, all the LED is always off. when I connect one LED to RxD, the LED is always on. the following is my code. `timescale 1ns / 1ps module receiver( input clk, //input clock input reset, //input reset input RxD, //input receving data line output [7:0]RxData, // output for 8 bits data output LED01, // output 8 LEDs output LED02 ); //internal variables reg shift; // shift signal to trigger shifting data reg state, nextstate; // initial state and next state variable reg [3:0] bitcounter; // 4 bits counter to count up to 9 for UART receiving reg [1:0] samplecounter; // 2 bits sample counter to count up to 4 for oversampling reg [13:0] counter; // 14 bits counter to count the baud rate reg [9:0] rxshiftreg; //bit shifting register reg clear_bitcounter,inc_bitcounter,inc_samplecounter,clear_samplecounter; //clear or increment the counter assign LED01=shift; assign LED02=nextstate; // constants parameter clk_freq = 100_000_000; // system clock frequency parameter baud_rate = 9_600; //baud rate parameter div_sample = 4; //oversampling parameter div_counter = clk_freq/(baud_rate*div_sample); // this is the number we have to divide the system clock frequency to get a frequency (div_sample) time higher than (baud_rate) parameter mid_sample = (div_sample/2); // this is the middle point of a bit where you want to sample it parameter div_bit = 10; // 1 start, 8 data, 1 stop assign RxData = rxshiftreg [8:1]; // assign the RxData from the shiftregister //UART receiver logic always @ (posedge clk) begin if (reset)begin // if reset is asserted state <=1; // set state to idle bitcounter <=0; // reset the bit counter counter <=0; // reset the counter samplecounter <=0; // reset the sample counter end else begin // if reset is not asserted counter <= counter +1; // start count in the counter if (counter >= div_counter-1) begin // if counter reach the baud rate with sampling counter <=0; //reset the counter state <= nextstate; // assign the state to nextstate if (shift)rxshiftreg <= {RxD,rxshiftreg[9:1]}; //if shift asserted, load the receiving data if (clear_samplecounter) samplecounter <=0; // if clear sampl counter asserted, reset sample counter if (inc_samplecounter) samplecounter <= samplecounter +1; //if increment counter asserted, start sample count if (clear_bitcounter) bitcounter <=0; // if clear bit counter asserted, reset bit counter if (inc_bitcounter)bitcounter <= bitcounter +1; // if increment bit counter asserted, start count bit counter end end end //state machine always @ (posedge clk) //trigger by clock begin shift <= 0; // set shift to 0 to avoid any shifting clear_samplecounter <=0; // set clear sample counter to 0 to avoid reset inc_samplecounter <=0; // set increment sample counter to 0 to avoid any increment clear_bitcounter <=0; // set clear bit counter to 0 to avoid claring inc_bitcounter <=0; // set increment bit counter to avoid any count nextstate <=1; // set next state to be idle state case (state) 0: begin // idle state if (RxD) // if input RxD data line asserted begin nextstate <=0; // back to idle state because RxD needs to be low to start transmission end else begin // if input RxD data line is not asserted nextstate <=1; //jump to receiving state clear_bitcounter <=1; // trigger to clear bit counter clear_samplecounter <=1; // trigger to clear sample counter end end 1: begin // receiving state nextstate <= 1; // DEFAULT if (samplecounter== mid_sample-1) shift <= 1; // if sample counter is 1, trigger shift //LED<=1; if (samplecounter== div_sample - 1) begin // if sample counter is 3 as the sample rate used is 3 if (bitcounter == div_bit - 1) begin // check if bit counter if 9 or not nextstate <= 0; // back to idle state if bit counter is 9 as receving is complete end inc_bitcounter <=1; // trigger the increment bit counter if bit counter is not 9 clear_samplecounter <=1; //trigger the sample counter to reset the sample counter end else inc_samplecounter <=1; // if sample is not equal to 3, keep counting end default: nextstate <=0; //default idle state endcase end endmodule
  2. Hello, I am trying to send a character to FPGA from PC hyper terminal , for eg : 's' to start other processes in FPGA like initiating generation of CCD signals and sampling ADC et al and a different ascii character to stop the processes. I am able to send a ASCII character from PC hyper terminal and receive binary value it on FPGA LED's however I'm unable to use this for control. Please find my top level code below. 'Start' signal is to be controlling the initiation of other processes. library IEEE; use IEEE.STD_LOGIC_1164.ALL; use IEEE.NUMERIC_STD.ALL; Library UNISIM; use UNISIM.vcomponents.all; Library UNIMACRO; use UNIMACRO.vcomponents.all; use IEEE.MATH_REAL.ALL; ----------------------------------------------------- entity top_module is port( --------------------UART_GUI------------------------------- RxD : IN STD_LOGIC; RxData : INOUT STD_LOGIC_VECTOR(7 DOWNTO 0); ---COMMON INPUTS--- clk, rst : in std_logic; --send_ccd : in std_logic;---------------CCD control SH,ICG,master_ccd_clock : out std_logic; ----FOR AD7980-------- --sample: in std_logic; -------------- to start sampling samp_ind: out std_logic;---------------indicates sampling in process adc_cnv : out std_logic;---------------cnv for AD7980 adc_clk : inout std_logic;--------------SPI clock adc_miso : in std_logic;------------------output from AD7980 -------FIFO SIGNALS-------- WriteEn , ReadEn : in std_logic; -------------fifo controls full, empty : out std_logic ------------------indicates fifo status ); end top_module; architecture structural of top_module is ----------------------------------------------------------------------------UART CONTROL GUI------------------------------------- component receiver IS PORT ( clk : IN STD_LOGIC; reset : IN STD_LOGIC; RxD : IN STD_LOGIC; RxData : INOUT STD_LOGIC_VECTOR(7 DOWNTO 0) ); END component receiver; ----------------------------------------FIFO COMPONENT DECLARATION ----------------------------------------------------------------- component fifo is port ( reset_rtl_0 : in STD_LOGIC; clk_100MHz : in STD_LOGIC; full_0 : out STD_LOGIC; din_0 : in STD_LOGIC_VECTOR ( 15 downto 0 ); wr_en_0 : in STD_LOGIC; empty_0 : out STD_LOGIC; dout_0 : out STD_LOGIC_VECTOR ( 15 downto 0 ); rd_en_0 : in STD_LOGIC ); end component fifo; -------------------------------------------------------------------------------------------------------------------------- signal fifo_data_out : STD_LOGIC_VECTOR (15 downto 0); signal adc_out : std_logic_vector(15 downto 0); signal start :std_logic; -------------------------UART_RX_FOR CONTROL_ OF_PROCESSES--------------------------------------------------------------- process(Clk,RxData) begin if RxData = "01110011" then start <= '1' ; elsif RxData = "01110000" then start <= '0'; else start <= '0'; end if; end process; --------------------AD7980PORTMAP---------------------------------------------------------------------------------- AD7980 : entity work.AD7980 port map ( clock => clk, sample => start, -- data output Dout => adc_out(15 downto 0), samp_ind => samp_ind, -- ADC connection adc_miso => adc_miso, adc_cnv => adc_cnv, adc_clk =>adc_clk ); ---------------------------------------------FIFO PORTMAP---------------------------------------------------------------- fifo_i: component fifo port map ( clk_100MHz => clk, din_0(15 downto 0) => adc_out(15 downto 0), dout_0(15 downto 0) => fifo_data_out(15 downto 0), empty_0 => empty, full_0 => full, rd_en_0 => ReadEn, reset_rtl_0 => rst, wr_en_0 => WriteEn ); ccd_control : entity work.TCD1103GFG port map ( clock => clk, send => start, SH => SH, ICG => ICG, master_ccd_clock => master_ccd_clock); ---------------------------------------------------------------UART GUI CONTROL--------------------------------------- uart_gui : entity work.receiver port map ( clk => clk, reset => rst, RxD => RxD, RxData => RxData ); end structural; Here is the UART receiver open source code I'm using that works LIBRARY ieee; USE ieee.std_logic_1164.all; USE ieee.std_logic_unsigned.all; use ieee.std_logic_arith.all; ENTITY receiver IS PORT ( clk : IN STD_LOGIC; reset : IN STD_LOGIC; RxD : IN STD_LOGIC; RxData : INOUT STD_LOGIC_VECTOR(7 DOWNTO 0) ); END receiver; ARCHITECTURE behavioural OF receiver IS SIGNAL shift : STD_LOGIC; SIGNAL state : STD_LOGIC; SIGNAL nextstate : STD_LOGIC; SIGNAL bitcounter : STD_LOGIC_VECTOR(3 DOWNTO 0); SIGNAL samplecounter : STD_LOGIC_VECTOR(1 DOWNTO 0); SIGNAL counter : STD_LOGIC_VECTOR(13 DOWNTO 0); SIGNAL rxshiftreg : STD_LOGIC_VECTOR(9 DOWNTO 0); SIGNAL clear_bitcounter : STD_LOGIC; SIGNAL inc_bitcounter : STD_LOGIC; SIGNAL inc_samplecounter : STD_LOGIC; SIGNAL clear_samplecounter : STD_LOGIC; constant clk_freq: integer := 100000000; constant baud_rate :integer := 9600; constant div_sample :integer := 4; constant div_counter :integer := (clk_freq/(baud_rate*div_sample)); constant mid_sample : integer := (div_sample/2); constant div_bit : integer := 10; BEGIN RxData <= rxshiftreg(8 DOWNTO 1); PROCESS (clk) BEGIN IF (clk'EVENT AND clk = '1') THEN IF (reset = '1') THEN state <= '0'; bitcounter <= "0000"; counter <= "00000000000000"; samplecounter <= "00"; ELSE counter <= counter + "00000000000001"; if (counter>= div_counter - 1) then counter <= "00000000000000"; state <= nextstate; IF (shift = '1') THEN rxshiftreg <= (RxD & rxshiftreg(9 DOWNTO 1)); END IF; IF (clear_samplecounter = '1') THEN samplecounter <= "00"; END IF; IF (inc_samplecounter = '1') THEN samplecounter <= samplecounter + "01"; END IF; IF (clear_bitcounter = '1') THEN bitcounter <= "0000"; END IF; IF (inc_bitcounter = '1') THEN bitcounter <= bitcounter + "0001"; END IF; END IF; END IF; END IF; END PROCESS; PROCESS (clk) BEGIN IF (clk'EVENT AND clk = '1') THEN shift <= '0'; clear_samplecounter <= '0'; inc_samplecounter <= '0'; clear_bitcounter <= '0'; inc_bitcounter <= '0'; nextstate <= '0'; CASE state IS WHEN '0' => IF (RxD = '1') THEN nextstate <= '0'; ELSE nextstate <= '1'; clear_bitcounter <= '1'; clear_samplecounter <= '1'; END IF; WHEN '1' => nextstate <= '1'; IF (samplecounter = (mid_sample - 1)) THEN shift <= '1'; END IF; IF (samplecounter = (div_sample - 1)) THEN IF (bitcounter = (div_bit - 1)) THEN nextstate <= '0'; END IF; inc_bitcounter <= '1'; clear_samplecounter <= '1'; ELSE inc_samplecounter <= '1'; END IF; WHEN OTHERS => nextstate <= '0'; END CASE; END IF; END PROCESS; end behavioural; I'm unsure if the issue is because of the number of clock cycles for which the character 's' exists. Please help me understand the miss here.