My goal was to drive a servo from the CPLD using VHDL. I've attached the project and source in case anyone else is pulling their hair out looking for a simple tutorial to work with their new design board. This is all assuming you are using the 50 MHz clock on the dev board with the Max II.
Good Luck!
VHDL Code for PWM output
20 ms signal generator output tck should be routed to the servo drive tck input.
20 ms signal generator
-- Generated by Quartus II Version 10.1 (Build Build 153 11/29/2010)
-- Created on Sun Jan 09 00:51:34 2011
LIBRARY ieee;
USE ieee.std_logic_1164.all;
-- Entity Declaration
ENTITY freq_div IS
-- {{ALTERA_IO_BEGIN}} DO NOT REMOVE THIS LINE!
PORT
(
clk : IN STD_LOGIC;
tck : OUT STD_LOGIC
);
-- {{ALTERA_IO_END}} DO NOT REMOVE THIS LINE!
END freq_div;
-- Architecture Body
ARCHITECTURE freq_div_architecture OF freq_div IS
signal count : INTEGER := 0;
signal x : STD_LOGIC := '0';
BEGIN
process(clk)
begin
if (clk'event and clk = '1') then
tck <= x;
if (count = 1000000) then -- convert 20 ns clk to 20 ms tcks
x <= '1';
count <= 0;
else
x <= '0';
count <= count + 1;
end if;
end if;
end process;
END freq_div_architecture;
Servo Driver
-- Generated by Quartus II Version 10.1 (Build Build 153 11/29/2010)
-- Created on Sun Jan 09 20:59:28 2011
LIBRARY ieee;
USE ieee.std_logic_1164.all;
-- Entity Declaration
ENTITY servo_driver IS
-- {{ALTERA_IO_BEGIN}} DO NOT REMOVE THIS LINE!
PORT
(
clk : IN STD_LOGIC;
tck : IN STD_LOGIC;
en : IN STD_LOGIC;
pwm : OUT STD_LOGIC
);
-- {{ALTERA_IO_END}} DO NOT REMOVE THIS LINE!
END servo_driver;
-- Architecture Body
ARCHITECTURE servo_driver_architecture OF servo_driver IS
signal count : INTEGER := 0;
signal pos : STD_LOGIC := '0'; -- servo position 0 or 90 deg.
signal x, y : STD_LOGIC := '0';
BEGIN
process(clk, tck)
begin
if (clk'event and clk = '1') then
if (tck = '1') then
x <= '1';
pos <= en;
end if;
pwm <= x;
if (x = '1') then
count <= count + 1;
else
count <= 0;
end if;
-- count = 50000; convert 20ns to 2ms = 90 deg.
-- count = 100000; convert 20ns to 1ms = 0 deg.
if ((pos = '1' and count = 50000) or (pos = '0' and count = 100000)) then
x <= '0';
end if;
end if;
end process;
END servo_driver_architecture;
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