199 lines
9.5 KiB
VHDL
199 lines
9.5 KiB
VHDL
LIBRARY IEEE;
|
|
USE IEEE.STD_LOGIC_1164.ALL;
|
|
|
|
-- Entity: digilent_jstk2
|
|
-- Purpose: Interface controller for the Digilent JSTK2 joystick module via SPI
|
|
-- Sends LED color commands and receives joystick/button data
|
|
ENTITY digilent_jstk2 IS
|
|
GENERIC (
|
|
DELAY_US : INTEGER := 25; -- Delay (in microseconds) between two SPI packets
|
|
CLKFREQ : INTEGER := 100_000_000; -- Frequency of the aclk signal (in Hz)
|
|
SPI_SCLKFREQ : INTEGER := 5_000 -- Frequency of the SPI SCLK clock signal (in Hz)
|
|
);
|
|
PORT (
|
|
aclk : IN STD_LOGIC; -- Main clock input
|
|
aresetn : IN STD_LOGIC; -- Active-low asynchronous reset
|
|
|
|
-- AXI4-Stream Master Interface: Data going TO the SPI IP-Core (and so, to the JSTK2 module)
|
|
m_axis_tvalid : OUT STD_LOGIC; -- Output data valid signal
|
|
m_axis_tdata : OUT STD_LOGIC_VECTOR(7 DOWNTO 0); -- 8-bit data to send via SPI
|
|
m_axis_tready : IN STD_LOGIC; -- SPI IP-Core ready to accept data
|
|
|
|
-- AXI4-Stream Slave Interface: Data coming FROM the SPI IP-Core (and so, from the JSTK2 module)
|
|
-- Note: There is no tready signal, so you must be always ready to accept incoming data, or it will be lost!
|
|
s_axis_tvalid : IN STD_LOGIC; -- Input data valid signal
|
|
s_axis_tdata : IN STD_LOGIC_VECTOR(7 DOWNTO 0); -- 8-bit data received via SPI
|
|
|
|
-- Joystick and button values read from the JSTK2 module
|
|
jstk_x : OUT STD_LOGIC_VECTOR(9 DOWNTO 0); -- X-axis joystick position (10-bit, 0-1023)
|
|
jstk_y : OUT STD_LOGIC_VECTOR(9 DOWNTO 0); -- Y-axis joystick position (10-bit, 0-1023)
|
|
btn_jstk : OUT STD_LOGIC; -- Joystick button state (1=pressed)
|
|
btn_trigger : OUT STD_LOGIC; -- Trigger button state (1=pressed)
|
|
|
|
-- LED color values to send to the JSTK2 module
|
|
led_r : IN STD_LOGIC_VECTOR(7 DOWNTO 0); -- Red LED intensity (0-255)
|
|
led_g : IN STD_LOGIC_VECTOR(7 DOWNTO 0); -- Green LED intensity (0-255)
|
|
led_b : IN STD_LOGIC_VECTOR(7 DOWNTO 0) -- Blue LED intensity (0-255)
|
|
);
|
|
END digilent_jstk2;
|
|
|
|
ARCHITECTURE Behavioral OF digilent_jstk2 IS
|
|
|
|
-- Command code for the SetLEDRGB command, see the JSTK2 datasheet
|
|
CONSTANT CMDSETLEDRGB : STD_LOGIC_VECTOR(7 DOWNTO 0) := x"84";
|
|
|
|
-- Calculate delay in clock cycles: (delay_period + 1_SPI_clock_period) * clock_frequency
|
|
-- This ensures proper timing between SPI packets as required by JSTK2 datasheet
|
|
CONSTANT DELAY_CLK_CYCLES : INTEGER := (DELAY_US + 1_000_000 / SPI_SCLKFREQ) * (CLKFREQ / 1_000_000) - 1;
|
|
|
|
-- State machine type definitions
|
|
TYPE tx_state_type IS (DELAY, SEND_CMD, SEND_RED, SEND_GREEN, SEND_BLUE, SEND_DUMMY);
|
|
TYPE rx_state_type IS (JSTK_X_LOW, JSTK_X_HIGH, JSTK_Y_LOW, JSTK_Y_HIGH, BUTTONS);
|
|
|
|
-- State machine signals
|
|
SIGNAL tx_state : tx_state_type := DELAY; -- Transmit state machine current state
|
|
SIGNAL rx_state : rx_state_type := JSTK_X_LOW; -- Receive state machine current state
|
|
|
|
-- Timing and data storage signals
|
|
SIGNAL tx_delay_counter : INTEGER RANGE 0 TO DELAY_CLK_CYCLES := 0; -- Counter for inter-packet delay timing
|
|
SIGNAL rx_cache : STD_LOGIC_VECTOR(s_axis_tdata'range); -- Temporary storage for multi-byte data reception
|
|
|
|
BEGIN
|
|
|
|
-- Output valid signal control: Set to '1' when we want to send data to SPI IP-Core
|
|
-- Only inactive during DELAY state when waiting between packets
|
|
WITH tx_state SELECT m_axis_tvalid <=
|
|
'0' WHEN DELAY, -- No transmission during delay
|
|
'1' WHEN SEND_CMD, -- Send command byte
|
|
'1' WHEN SEND_RED, -- Send red LED value
|
|
'1' WHEN SEND_GREEN, -- Send green LED value
|
|
'1' WHEN SEND_BLUE, -- Send blue LED value
|
|
'1' WHEN SEND_DUMMY; -- Send dummy byte to complete transaction
|
|
|
|
-- Output data multiplexer: Select what data to send based on current TX state
|
|
WITH tx_state SELECT m_axis_tdata <=
|
|
(OTHERS => '0') WHEN DELAY, -- No data during delay
|
|
CMDSETLEDRGB WHEN SEND_CMD, -- SetLEDRGB command (0x84)
|
|
led_r WHEN SEND_RED, -- Red LED intensity value
|
|
led_g WHEN SEND_GREEN, -- Green LED intensity value
|
|
led_b WHEN SEND_BLUE, -- Blue LED intensity value
|
|
"01101001" WHEN SEND_DUMMY; -- Dummy byte to complete 5-byte transaction
|
|
|
|
-- TX State Machine: Sends LED color commands to JSTK2 module
|
|
-- Protocol: Command(1) + Red(1) + Green(1) + Blue(1) + Dummy(1) = 5 bytes total > Delay before next command
|
|
-- The delay is required by the JSTK datasheet to ensure proper timing between SPI transactions
|
|
TX : PROCESS (aclk)
|
|
BEGIN
|
|
IF rising_edge(aclk) THEN
|
|
IF aresetn = '0' THEN
|
|
-- Reset: Start in delay state with counter cleared
|
|
tx_state <= DELAY;
|
|
tx_delay_counter <= 0;
|
|
|
|
ELSE
|
|
|
|
CASE tx_state IS
|
|
|
|
WHEN DELAY =>
|
|
-- Wait for required delay period between SPI transactions
|
|
IF tx_delay_counter = DELAY_CLK_CYCLES THEN
|
|
tx_delay_counter <= 0; -- Reset counter
|
|
tx_state <= SEND_CMD; -- Start new transmission
|
|
ELSE
|
|
tx_delay_counter <= tx_delay_counter + 1; -- Continue counting
|
|
END IF;
|
|
|
|
WHEN SEND_CMD =>
|
|
-- Send SetLEDRGB command byte
|
|
IF m_axis_tready = '1' THEN
|
|
tx_state <= SEND_RED; -- Move to red LED transmission
|
|
END IF;
|
|
|
|
WHEN SEND_RED =>
|
|
-- Send red LED intensity value
|
|
IF m_axis_tready = '1' THEN
|
|
tx_state <= SEND_GREEN; -- Move to green LED transmission
|
|
END IF;
|
|
|
|
WHEN SEND_GREEN =>
|
|
-- Send green LED intensity value
|
|
IF m_axis_tready = '1' THEN
|
|
tx_state <= SEND_BLUE; -- Move to blue LED transmission
|
|
END IF;
|
|
|
|
WHEN SEND_BLUE =>
|
|
-- Send blue LED intensity value
|
|
IF m_axis_tready = '1' THEN
|
|
tx_state <= SEND_DUMMY; -- Move to dummy byte transmission
|
|
END IF;
|
|
|
|
WHEN SEND_DUMMY =>
|
|
-- Send dummy byte to complete 5-byte transaction
|
|
IF m_axis_tready = '1' THEN
|
|
tx_state <= DELAY; -- Return to delay state
|
|
END IF;
|
|
|
|
END CASE;
|
|
END IF;
|
|
END IF;
|
|
END PROCESS TX;
|
|
|
|
-- RX State Machine: Receives 5 bytes of response data and updates outputs
|
|
-- Protocol: X_low(1) + X_high(1) + Y_low(1) + Y_high(1) + Buttons(1) = 5 bytes total
|
|
RX : PROCESS (aclk)
|
|
BEGIN
|
|
IF rising_edge(aclk) THEN
|
|
|
|
IF aresetn = '0' THEN
|
|
-- Reset: Start waiting for X-axis low byte
|
|
rx_state <= JSTK_X_LOW;
|
|
rx_cache <= (OTHERS => '0');
|
|
|
|
ELSE
|
|
|
|
CASE rx_state IS
|
|
|
|
WHEN JSTK_X_LOW =>
|
|
-- Receive X-axis low byte (bits 7:0)
|
|
IF s_axis_tvalid = '1' THEN
|
|
rx_cache <= s_axis_tdata; -- Store low byte temporarily
|
|
rx_state <= JSTK_X_HIGH; -- Wait for high byte
|
|
END IF;
|
|
|
|
WHEN JSTK_X_HIGH =>
|
|
-- Receive X-axis high byte (bits 9:8) and assemble complete X value
|
|
IF s_axis_tvalid = '1' THEN
|
|
-- Combine: high_byte(1:0) & low_byte(7:0) = 10-bit X position
|
|
jstk_x <= s_axis_tdata(1 DOWNTO 0) & rx_cache;
|
|
rx_state <= JSTK_Y_LOW; -- Move to Y-axis reception
|
|
END IF;
|
|
|
|
WHEN JSTK_Y_LOW =>
|
|
-- Receive Y-axis low byte (bits 7:0)
|
|
IF s_axis_tvalid = '1' THEN
|
|
rx_cache <= s_axis_tdata; -- Store low byte temporarily
|
|
rx_state <= JSTK_Y_HIGH; -- Wait for high byte
|
|
END IF;
|
|
|
|
WHEN JSTK_Y_HIGH =>
|
|
-- Receive Y-axis high byte (bits 9:8) and assemble complete Y value
|
|
IF s_axis_tvalid = '1' THEN
|
|
-- Combine: high_byte(1:0) & low_byte(7:0) = 10-bit Y position
|
|
jstk_y <= s_axis_tdata(1 DOWNTO 0) & rx_cache;
|
|
rx_state <= BUTTONS; -- Move to button reception
|
|
END IF;
|
|
|
|
WHEN BUTTONS =>
|
|
-- Receive button states byte
|
|
IF s_axis_tvalid = '1' THEN
|
|
btn_jstk <= s_axis_tdata(0); -- Joystick button (bit 0)
|
|
btn_trigger <= s_axis_tdata(1); -- Trigger button (bit 1)
|
|
rx_state <= JSTK_X_LOW; -- Return to start for next packet
|
|
END IF;
|
|
|
|
END CASE;
|
|
END IF;
|
|
END IF;
|
|
END PROCESS RX;
|
|
|
|
END ARCHITECTURE; |