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/trunk/lpd8806_pack.vhd
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--------------------------------------------------------------------------
-- Package of dds components
--
--
 
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
 
package lpd8806_pack is
 
component lpd8806_LED_chain_driver
generic (
SCLK_FREQ : real; -- Desired lpd8806 serial clock frequency
UPDATE_FREQ : real; -- Desired LED chain update frequency
SYS_CLK_RATE : real; -- underlying clock rate
N_LEDS : integer -- Number of LEDs in chain
);
port (
 
-- System Clock, Reset and Clock Enable
sys_rst_n : in std_logic;
sys_clk : in std_logic;
sys_clk_en : in std_logic;
 
-- Selection of color information
c_adr_o : out unsigned(7 downto 0);
c_dat_i : in unsigned(6 downto 0);
 
-- Output
sclk_o : out std_logic;
sdat_o : out std_logic
);
end component;
 
component spi_byte_writer
generic (
SCLK_FREQ : real; -- Desired lpd8806 serial clock frequency
SYS_CLK_RATE : real -- underlying clock rate
);
port (
 
-- System Clock, Reset and Clock Enable
sys_rst_n : in std_logic;
sys_clk : in std_logic;
sys_clk_en : in std_logic;
 
-- Data to send.
sel_i : in std_logic;
we_i : in std_logic;
dat_i : in unsigned(7 downto 0);
 
-- Output
ssel_o : out std_logic;
sclk_o : out std_logic;
sdat_o : out std_logic
);
end component;
 
end lpd8806_pack;
 
package body lpd8806_pack is
end lpd8806_pack;
 
-------------------------------------------------------------------------------
-- LPD8806 "GRB" LED chain driver module
-------------------------------------------------------------------------------
--
-- Author: John Clayton
-- Update: Apr. 8, 2013 Started Coding, wrote description.
-- Apr. 10, 2013 Simulated and tested in hardware, with
-- semi-satisfactory results. All is not yet well.
--
-- Description
-------------------------------------------------------------------------------
-- This module outputs a serial stream of clock and data pulses which
-- are intended for driving a chain of LPD8806 LED PWM driver ICs.
--
-- This type of LED driver is commonly sold pre-built into strips
-- of LEDs, with each LPD8806 circuit driving two multi-color LEDs.
--
-- The LEDs are driven with 21-bit color, that is 7 bits for red
-- intensity, 7 bits for green intensity and 7 bits for blue intensity.
--
-- I stopped short of calling it an "RGB LED driver" since lpd8806
-- receives the data in the order "GRB." The ordering of the color
-- bits should not really matter anyway, so just be happy, OK?
--
-- The first bit, the MSB, is set for updating the LED colors, and cleared
-- for resetting the drivers. Therefore, after each sequence of color
-- information bits, about 24 bits of zero are sent out to reset
-- everything in order to be ready for the next update.
--
-- This module generates its own serial bit clock by using a DDS based
-- on the underlying system clock rate. It has been suggested that
-- 2 MHz is a good number, although I'll bet many other speeds will
-- also work, both higher and lower.
--
-- Another DDS generates the update rate pulse, which kicks off
-- the updating process. Beware, if one sets the update rate too
-- high, it may become impossible to transmit all the required color
-- bits, and so the LEDs at the end of the chain may get left out
-- of the process!
--
-- Yes, that is correct, the LEDs closest to the source of SCLK
-- and SDAT get lit first, then they become "passthrough" so that
-- the next one gets set, and so forth.
--
-- This module latches color information from an external source.
-- It provides the c_adr_o signal to specify which information
-- should be selected. In this way, the module can be used with
-- different numbers of drivers and LED pairs in the strip.
--
-- Just to keep things on an even keel, the c_adr_o address
-- advances according to the following pattern:
--
-- 0,1,2,4,5,6,8,9,A,C,D,E...
--
-- What is happening is that one address per LED is getting skipped
-- or "wasted" in order to start with each LEDs green value on an
-- even multiple N*4, where N is the LED number, beginning with zero
-- for the "zeroth" LED. Then the red values are at N*4+1, while
-- the blue values are at N*4+2. The N*4+3 values are simply skipped.
-- Isn't that super organized?
--
--
 
 
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;
use IEEE.MATH_REAL.ALL;
 
library work;
use work.dds_pack.all;
 
entity lpd8806_LED_chain_driver is
generic (
SCLK_FREQ : real; -- Desired lpd8806 serial clock frequency
UPDATE_FREQ : real; -- Desired LED chain update frequency
SYS_CLK_RATE : real; -- underlying clock rate
N_LEDS : integer -- Number of LEDs in chain
);
port (
 
-- System Clock, Reset and Clock Enable
sys_rst_n : in std_logic;
sys_clk : in std_logic;
sys_clk_en : in std_logic;
 
-- Selection of color information
c_adr_o : out unsigned(7 downto 0);
c_dat_i : in unsigned(6 downto 0);
 
-- Output
sclk_o : out std_logic;
sdat_o : out std_logic
);
end lpd8806_LED_chain_driver;
 
architecture beh of lpd8806_LED_chain_driver is
 
-- Constants
constant N_ZERO_BYTES : natural := 3;
 
-- Signals
signal sclk : std_logic;
signal sclk_pulse : std_logic;
signal update_pulse : std_logic;
signal bit_count : unsigned(3 downto 0);
signal byte_count : unsigned(7 downto 0); -- Widen for chains of 64+ LEDs.
signal c_adr : unsigned(7 downto 0); -- Widen for chains of 64+ LEDs.
signal c_dat : unsigned(7 downto 0);
 
-----------------------------------------------------------------------------
begin
 
c_adr_proc: Process(sys_rst_n,sys_clk)
begin
if (sys_rst_n = '0') then
byte_count <= (others=>'0');
c_adr <= (others=>'0');
c_dat <= (others=>'0');
bit_count <= (others=>'0');
elsif (sys_clk'event and sys_clk='1') then
if (sys_clk_en='1') then
if (byte_count=0) then
c_adr <= (others=>'0');
end if;
if (byte_count>0 and sclk_pulse='1') then
bit_count <= bit_count-1;
if (bit_count<8) then
c_dat <= c_dat(6 downto 0) & '0'; -- Default is to shift color data
if (bit_count=0) then
byte_count <= byte_count-1;
bit_count <= to_unsigned(7,bit_count'length);
-- Set color data MSB appropriately
if (byte_count<=4) then
c_dat <= (others=>'0');
else
c_dat <= '1' & c_dat_i;
end if;
-- Cause c_adr to skip every address.ending in "11"
if (c_adr(1 downto 0)="10") then
c_adr <= c_adr+2;
else
c_adr <= c_adr+1;
end if;
end if;
end if;
end if;
-- Update pulse gets highest priority
if (update_pulse='1') then
byte_count <= to_unsigned(N_LEDS*3+1+N_ZERO_BYTES,byte_count'length);
if (sclk_pulse='1') then
bit_count <= to_unsigned(7,bit_count'length);
else
bit_count <= to_unsigned(8,bit_count'length); -- means "pending"
end if;
c_dat <= '1' & c_dat_i;
c_adr <= c_adr+1;
end if;
end if;
end if; -- sys_clk
end process;
sdat_o <= c_dat(7) when (byte_count>0 and bit_count<8) else '0';
c_adr_o <= c_adr;
 
-------------------------
-- Update pulse generation
update_gen: dds_constant_squarewave
generic map(
OUTPUT_FREQ => UPDATE_FREQ, -- Desired output frequency
SYS_CLK_RATE => SYS_CLK_RATE, -- underlying clock rate
ACC_BITS => 24 -- Bit width of DDS phase accumulator
)
port map(
sys_rst_n => sys_rst_n,
sys_clk => sys_clk,
sys_clk_en => sys_clk_en,
 
-- Output
pulse_o => update_pulse,
squarewave_o => open
);
 
-------------------------
-- Serial clock generation
sclk_gen: dds_constant_squarewave
generic map(
OUTPUT_FREQ => SCLK_FREQ, -- Desired output frequency
SYS_CLK_RATE => SYS_CLK_RATE, -- underlying clock rate
ACC_BITS => 16 -- Bit width of DDS phase accumulator
)
port map(
sys_rst_n => sys_rst_n,
sys_clk => sys_clk,
sys_clk_en => sys_clk_en,
 
-- Output
pulse_o => sclk_pulse,
squarewave_o => sclk
);
sclk_o <= not sclk when (byte_count>0 and bit_count<8) else '0';
 
end beh;
 
 
-------------------------------------------------------------------------------
-- SPI byte writer module
-------------------------------------------------------------------------------
--
-- Author: John Clayton
-- Update: Apr. 8, 2013 Started Coding, wrote description.
--
-- Description
-------------------------------------------------------------------------------
-- I conceived of this module while debugging a serial driver for a
-- string of LPD8806 LED drivers. It essentially latches the input
-- data, and sends it out serially at the desired rate. When the byte
-- is fully transmitted, it stops and waits for the next byte.
--
-- The output clock is gated by ssel_o. If you need a continuous
-- clock, please ungate it yourself.
--
-- Unlike with asynchronous data which shift out the lsb first, this
-- unit shifts out the msb first.
--
 
 
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;
use IEEE.MATH_REAL.ALL;
 
library work;
use work.dds_pack.all;
 
entity spi_byte_writer is
generic (
SCLK_FREQ : real; -- Desired lpd8806 serial clock frequency
SYS_CLK_RATE : real -- underlying clock rate
);
port (
 
-- System Clock, Reset and Clock Enable
sys_rst_n : in std_logic;
sys_clk : in std_logic;
sys_clk_en : in std_logic;
 
-- Data to send.
sel_i : in std_logic;
we_i : in std_logic;
dat_i : in unsigned(7 downto 0);
 
-- Output
ssel_o : out std_logic;
sclk_o : out std_logic;
sdat_o : out std_logic
);
end spi_byte_writer;
 
architecture beh of spi_byte_writer is
 
-- Signals
signal sclk : std_logic;
signal sclk_pulse : std_logic;
signal ssel : std_logic;
signal sdat : unsigned(7 downto 0);
signal bit_count : unsigned(3 downto 0);
 
-----------------------------------------------------------------------------
begin
 
spi_write_proc: Process(sys_rst_n,sys_clk)
begin
if (sys_rst_n = '0') then
sdat <= (others=>'0');
bit_count <= (others=>'0');
elsif (sys_clk'event and sys_clk='1') then
if (sys_clk_en='1') then
if (sclk_pulse='1') then
if (bit_count>0) then
bit_count <= bit_count-1;
end if;
if ssel='1' then
sdat <= sdat(6 downto 0) & '0';
end if;
elsif (sel_i='1' and we_i='1') then
if (sclk_pulse='1') then
bit_count <= to_unsigned(8,bit_count'length);
else
bit_count <= to_unsigned(9,bit_count'length); -- means "pending"
end if;
sdat <= dat_i;
end if;
end if;
end if; -- sys_clk
end process;
sdat_o <= sdat(7) when ssel='1' else '0';
 
-------------------------
-- Serial clock generation
sclk_gen: dds_constant_squarewave
generic map(
OUTPUT_FREQ => SCLK_FREQ, -- Desired output frequency
SYS_CLK_RATE => SYS_CLK_RATE, -- underlying clock rate
ACC_BITS => 16 -- Bit width of DDS phase accumulator
)
port map(
sys_rst_n => sys_rst_n,
sys_clk => sys_clk,
sys_clk_en => sys_clk_en,
 
-- Output
pulse_o => sclk_pulse,
squarewave_o => sclk
);
sclk_o <= not sclk when ssel='1' else '0';
ssel <= '1' when (bit_count<9 and bit_count>0) else '0';
ssel_o <= ssel;
 
end beh;
 
 

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