mirror of
https://github.com/RobotechLille/cdf2018-principal
synced 2024-05-21 22:26:13 +02:00
70 lines
3.2 KiB
VHDL
70 lines
3.2 KiB
VHDL
LIBRARY ieee;
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USE ieee.std_logic_1164.all;
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USE ieee.std_logic_unsigned.all;
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USE ieee.std_logic_arith.all;
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ENTITY hcSr04 IS
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GENERIC(
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fFpga : INTEGER := 50_000_000; -- frequency of the FPGA clock (Hz)
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maxOutput : INTEGER := 65535 -- maximum number to store the distance
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);
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PORT(
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clk : IN STD_LOGIC; -- clock of the FPGA
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echo : IN STD_LOGIC; -- echo pin of the hcSr04
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distance : OUT INTEGER RANGE 0 TO maxOutput; -- Ranges from 0 to 4 meters, 0 if no data
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trigger : OUT STD_LOGIC; -- trigger pin of the hcSr04
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start : IN STD_LOGIC; -- Set to '1' everytime a measurement is needed (or keep at '1' for continuous measurement)
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finished : OUT STD_LOGIC -- Driven to '1' everytime a measurement has finished
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);
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END hcSr04;
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ARCHITECTURE Behavioral OF hcSr04 IS
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CONSTANT triggerTicks : INTEGER := fFPGA / 100000; -- Number of FPGA ticks that makes 10us (used for trigger)
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CONSTANT measurementTicks : INTEGER := fFPGA / 17; -- Number of FPGA ticks that makes 60ms (used for measurement cycles)
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CONSTANT maximumRange : INTEGER := 4; -- Maximum range the sensor can detect
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CONSTANT distanceTicks : INTEGER := maximumRange * fFPGA / 172; -- Number of FPGA ticks that makes the maximum distance that can be measured
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-- 172 = 1 / 58 s/m
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SIGNAL measurementCounter : INTEGER RANGE 0 to measurementTicks - 1 := 0; -- Progress in the measurement
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SIGNAL distanceCounter : INTEGER RANGE 0 to distanceTicks - 1 := 0; -- Ticks for wich echo has been at one
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SIGNAL triggerCounter : INTEGER RANGE 0 to triggerTicks - 1 := 0; -- Progress in the trigger
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TYPE stateType IS (init, waiting, triggering, measuring);
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SIGNAL state : stateType;
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BEGIN
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measure : process(clk)
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begin
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if rising_edge(clk) then
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CASE state IS
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WHEN init =>
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trigger <= '0';
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distance <= 0;
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state <= waiting;
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WHEN waiting =>
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finished <= '0';
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IF start = '1' THEN
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trigger <= '1';
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triggerCounter <= 0;
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state <= triggering;
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END IF;
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WHEN triggering =>
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triggerCounter <= triggerCounter + 1;
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IF triggerCounter = triggerTicks - 1 THEN
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trigger <= '0';
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measurementCounter <= 0;
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distanceCounter <= 0;
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state <= measuring;
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END IF;
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WHEN measuring =>
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IF echo = '1' and distanceCounter < distanceTicks THEN
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distanceCounter <= distanceCounter + 1;
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END IF;
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measurementCounter <= measurementCounter + 1;
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IF measurementCounter = measurementTicks - 1 THEN
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distance <= distanceCounter * maxOutput / distanceTicks;
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finished <= '1';
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state <= waiting;
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END IF;
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END CASE;
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end if;
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end process;
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END Behavioral;
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