I'm going to try out a VHDL driver for the Hitachi HD44780 LCD driver.
I've ported it for several microcontrollers (TI Hercules, Maxim MAX32660) and a Linux device in the past.
I was going to write a VHDL driver, but found a few potential candidates online. I'm going to try Daniel Kampert's HD44780 LCD-Interface.
Current status:
Looks like you're planning to control it with the PS
The goal is from both. It's pure VHDL so it can be used in the PL directly.
I have a PYNQ board, so I currently connected it to the PS. It allows me to use data and control pins from Python.
That said: the week-end is finished and it isn't working yet.
Current status:
VHDL ported from 8 to 4 data lines (I commented out 8-bit logic in the source of Daniel below)
----------------------------------------------------------------------------------
-- Company: https://www.kampis-elektroecke.de
-- Engineer: Daniel Kampert
--
-- Create Date: 24.01.2020 21:51:49
-- Design Name:
-- Module Name: LCD_Controller - LCD_Controller_Arch
-- Target Devices: XC7Z010CLG400-1
-- Tool Versions: Vivado 2020.1
-- Description: LCD interface for the HD44780 LCD-Interface tutorial from
-- https://www.kampis-elektroecke.de/fpga/hd44780-lcd-interface/
--
-- Dependencies:
--
-- Revision:
-- Revision 0.01 - File Created
--
-- Additional Comments:
--
----------------------------------------------------------------------------------
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
-- Uncomment the following library declaration if using
-- arithmetic functions with Signed or Unsigned values
--use IEEE.NUMERIC_STD.ALL;
-- Uncomment the following library declaration if instantiating
-- any Xilinx leaf cells in this code.
--library UNISIM;
--use UNISIM.VComponents.all;
entity LCD_Controller is
Generic ( CONFIG : INTEGER := 0; -- Default configuration index.
CLOCK_FREQ : INTEGER := 125 -- Input clock frequency in MHz.
);
Port ( Clock : in STD_LOGIC;
nReset : in STD_LOGIC;
-- Communication bus
-- Data : in STD_LOGIC_VECTOR(7 downto 0);
Data : in STD_LOGIC_VECTOR(3 downto 0);
Ready : out STD_LOGIC; -- Output to signal that the display controller is ready
Valid : in STD_LOGIC; -- Input to signal valid data
SendCommand : in STD_LOGIC; -- Handle the next data byte as command (High)
-- LCD bus
LCD_RS : out STD_LOGIC; -- Command (High) / Data (Low)
LCD_E : out STD_LOGIC; -- Low-High Transition: Display read RW and RS
-- High-Low Transition: Display read data from bus (RW Low)
-- Display put data on the bus (RW High)
LCD_RW : out STD_LOGIC; -- Read data (High) / Write data (Low)
-- LCD_Data: inout STD_LOGIC_VECTOR(7 downto 0) -- LCD data bus
LCD_Data: inout STD_LOGIC_VECTOR(3 downto 0) -- LCD data bus
);
end LCD_Controller;
architecture LCD_Controller_Arch of LCD_Controller is
type State_t is (Reset, Initialize, Idle, WaitBusy, Transmit);
-- type Config_t is array(0 to 1, 0 to 5) of STD_LOGIC_VECTOR(7 downto 0);
type Config_t is array(0 to 1, 0 to 11) of STD_LOGIC_VECTOR(3 downto 0);
constant RESET_DELAY_1 : INTEGER := 50000; -- Delay after power up in us
constant RESET_DELAY_2 : INTEGER := 4100; -- Delay after sending first initialization instruction in us
constant RESET_DELAY_3 : INTEGER := 100; -- Delay after sending second initialization instruction in us
constant RESET_DELAY_4 : INTEGER := 100; -- Delay after sending third initialization instruction in us
-- constant Configs : Config_t := ((x"39", x"06", x"17", x"0F", x"01", x"02"), -- Function set european character set
-- -- Entry mode set increment cursor by 1 not shifting display
-- -- Character mode and internal power on
-- -- Clear the display
-- -- Return cursor to home position
-- -- Display and blinking cursor on
-- (x"39", x"06", x"17", x"0C", x"01", x"02") -- Function set european character set
-- -- Entry mode set increment cursor by 1 not shifting display
-- -- Character mode and internal power on
-- -- Clear the display
-- -- Return cursor to home position
-- -- Display on
-- );
constant Configs : Config_t := (
(x"2", x"9",
x"0", x"6",
x"1", x"7",
x"0", x"F",
x"0", x"1",
x"0", x"2"),
-- Function set european character set
-- Entry mode set increment cursor by 1 not shifting display
-- Character mode and internal power on
-- Clear the display
-- Return cursor to home position
-- Display and blinking cursor on
(x"2", x"9",
x"0", x"6",
x"1", x"7",
x"0", x"C",
x"0", x"1",
x"0", x"2")
-- Function set european character set
-- Entry mode set increment cursor by 1 not shifting display
-- Character mode and internal power on
-- Clear the display
-- Return cursor to home position
-- Display on
);
constant RESET_DELAY : INTEGER := RESET_DELAY_2 + RESET_DELAY_3 + RESET_DELAY_4; -- Full reset delay after the power up reset
signal CurrentState : State_t := Reset;
-- signal Data_Int : STD_LOGIC_VECTOR(7 downto 0) := (others => '0');
signal Data_Int : STD_LOGIC_VECTOR(3 downto 0) := (others => '0');
begin
process(Clock, nReset)
-- Millisecond counter for state machine timing
variable usCounter : INTEGER := 0;
begin
if(nReset = '0') then
usCounter := 0;
Ready <= '0';
LCD_E <= '0';
LCD_RS <= '0';
LCD_RW <= '0';
LCD_Data <= (others => '0');
Data_Int <= (others => '0');
CurrentState <= Reset;
elsif(rising_edge(Clock)) then
case CurrentState is
-- The entry point for the state machine.
when Reset =>
usCounter := usCounter + 1;
if(usCounter < (RESET_DELAY_1 * CLOCK_FREQ)) then
CurrentState <= Reset;
else
usCounter := 0;
-- LCD_Data <= x"30";
LCD_Data <= x"3"; -- 4 bit
CurrentState <= Initialize;
end if;
-- Initialize the display controller with a default configuration.
when Initialize =>
usCounter := usCounter + 1;
-- -- Send three times 0x30 to put the LCD into 8-bit mode
-- Send three times 0x03 to put the LCD into 4-bit mode
if(usCounter < (RESET_DELAY_2 * CLOCK_FREQ)) then
LCD_E <= '1';
elsif(usCounter < ((RESET_DELAY_2 + 10) * CLOCK_FREQ)) then
LCD_E <= '0';
elsif(usCounter < ((RESET_DELAY_2 + RESET_DELAY_3 + 10) * CLOCK_FREQ)) then
LCD_E <= '1';
elsif(usCounter < ((RESET_DELAY_2 + RESET_DELAY_3 + 20) * CLOCK_FREQ)) then
LCD_E <= '0';
elsif(usCounter < ((RESET_DELAY_2 + RESET_DELAY_3 + RESET_DELAY_4 + 20) * CLOCK_FREQ)) then
LCD_E <= '1';
elsif(usCounter < ((RESET_DELAY_3 + RESET_DELAY_3 + RESET_DELAY_4 + 30) * CLOCK_FREQ)) then
LCD_E <= '0';
-- set 4 character mode
elsif(usCounter < ((RESET_DELAY + 40) * CLOCK_FREQ)) then
LCD_E <= '1';
LCD_Data <= x"2"; -- 4 bit
elsif(usCounter < ((RESET_DELAY + 50) * CLOCK_FREQ)) then
LCD_E <= '0';
-- Send the display configuration
-- elsif(usCounter < ((RESET_DELAY + 40) * CLOCK_FREQ)) then
elsif(usCounter < ((RESET_DELAY + 60) * CLOCK_FREQ)) then
LCD_E <= '1';
LCD_Data <= Configs(CONFIG, 0);
-- elsif(usCounter < ((RESET_DELAY + 50) * CLOCK_FREQ)) then
elsif(usCounter < ((RESET_DELAY + 70) * CLOCK_FREQ)) then
LCD_E <= '0';
-- elsif(usCounter < ((RESET_DELAY + 60) * CLOCK_FREQ)) then
elsif(usCounter < ((RESET_DELAY + 80) * CLOCK_FREQ)) then
LCD_E <= '1';
LCD_Data <= Configs(CONFIG, 1);
-- elsif(usCounter < ((RESET_DELAY + 70) * CLOCK_FREQ)) then
elsif(usCounter < ((RESET_DELAY + 90) * CLOCK_FREQ)) then
LCD_E <= '0';
-- elsif(usCounter < ((RESET_DELAY + 80) * CLOCK_FREQ)) then
elsif(usCounter < ((RESET_DELAY + 100) * CLOCK_FREQ)) then
LCD_E <= '1';
LCD_Data <= Configs(CONFIG, 2);
-- elsif(usCounter < ((RESET_DELAY + 90) * CLOCK_FREQ)) then
elsif(usCounter < ((RESET_DELAY + 110) * CLOCK_FREQ)) then
LCD_E <= '0';
-- elsif(usCounter < ((RESET_DELAY + 100) * CLOCK_FREQ)) then
elsif(usCounter < ((RESET_DELAY + 120) * CLOCK_FREQ)) then
LCD_E <= '1';
LCD_Data <= Configs(CONFIG, 3);
-- elsif(usCounter < ((RESET_DELAY + 110) * CLOCK_FREQ)) then
elsif(usCounter < ((RESET_DELAY + 130) * CLOCK_FREQ)) then
LCD_E <= '0';
-- elsif(usCounter < ((RESET_DELAY + 120) * CLOCK_FREQ)) then
elsif(usCounter < ((RESET_DELAY + 140) * CLOCK_FREQ)) then
LCD_E <= '1';
LCD_Data <= Configs(CONFIG, 4);
-- elsif(usCounter < ((RESET_DELAY + 130) * CLOCK_FREQ)) then
elsif(usCounter < ((RESET_DELAY + 150) * CLOCK_FREQ)) then
LCD_E <= '0';
-- elsif(usCounter < ((RESET_DELAY + 140) * CLOCK_FREQ)) then
elsif(usCounter < ((RESET_DELAY + 160) * CLOCK_FREQ)) then
LCD_E <= '1';
LCD_Data <= Configs(CONFIG, 5);
-- elsif(usCounter < ((RESET_DELAY + 150) * CLOCK_FREQ)) then
elsif(usCounter < ((RESET_DELAY + 170) * CLOCK_FREQ)) then
LCD_E <= '0';
elsif(usCounter < ((RESET_DELAY + 180) * CLOCK_FREQ)) then
LCD_E <= '1';
LCD_Data <= Configs(CONFIG, 6);
elsif(usCounter < ((RESET_DELAY + 190) * CLOCK_FREQ)) then
LCD_E <= '0';
elsif(usCounter < ((RESET_DELAY + 200) * CLOCK_FREQ)) then
LCD_E <= '1';
LCD_Data <= Configs(CONFIG, 7);
elsif(usCounter < ((RESET_DELAY + 210) * CLOCK_FREQ)) then
LCD_E <= '0';
elsif(usCounter < ((RESET_DELAY + 220) * CLOCK_FREQ)) then
LCD_E <= '1';
LCD_Data <= Configs(CONFIG, 8);
elsif(usCounter < ((RESET_DELAY + 230) * CLOCK_FREQ)) then
LCD_E <= '0';
elsif(usCounter < ((RESET_DELAY + 240) * CLOCK_FREQ)) then
LCD_E <= '1';
LCD_Data <= Configs(CONFIG, 9);
elsif(usCounter < ((RESET_DELAY + 250) * CLOCK_FREQ)) then
LCD_E <= '0';
elsif(usCounter < ((RESET_DELAY + 260) * CLOCK_FREQ)) then
LCD_E <= '1';
LCD_Data <= Configs(CONFIG, 10);
elsif(usCounter < ((RESET_DELAY + 270) * CLOCK_FREQ)) then
LCD_E <= '0';
elsif(usCounter < ((RESET_DELAY + 280) * CLOCK_FREQ)) then
LCD_E <= '1';
LCD_Data <= Configs(CONFIG, 11);
elsif(usCounter < ((RESET_DELAY + 290) * CLOCK_FREQ)) then
LCD_E <= '0';
-- Initialization complete. Wait for the display to become ready.
else
usCounter := 0;
CurrentState <= WaitBusy;
end if;
-- Read the BUSY-Flag from the display controller and check
-- if the controller is ready.
when WaitBusy =>
usCounter := usCounter + 1;
if(usCounter < (10 * CLOCK_FREQ)) then
LCD_RS <= '0';
LCD_RW <= '1';
LCD_E <= '1';
LCD_Data <= (others => 'Z');
elsif(usCounter < (20 * CLOCK_FREQ)) then
LCD_E <= '0';
else
usCounter := 0;
-- Check if the BUSY-Flag is set
-- if(LCD_Data(7) = '1') then
if(LCD_Data(3) = '1') then
Ready <= '0';
CurrentState <= WaitBusy;
else
Ready <= '1';
CurrentState <= Idle;
end if;
end if;
-- Wait for a new data transmission.
when Idle =>
if(Valid = '1') then
Ready <= '0';
Data_Int <= Data;
if(SendCommand = '1') then
LCD_RS <= '0';
else
LCD_RS <= '1';
end if;
CurrentState <= Transmit;
else
Ready <= '1';
CurrentState <= Idle;
end if;
-- Write the data into the display controller.
when Transmit =>
usCounter := usCounter + 1;
if(usCounter < (10 * CLOCK_FREQ)) then
LCD_RW <= '0';
LCD_E <= '1';
LCD_Data <= Data_Int;
elsif(usCounter < (20 * CLOCK_FREQ)) then
LCD_E <= '0';
else
usCounter := 0;
CurrentState <= WaitBusy;
end if;
end case;
end if;
end process;
end LCD_Controller_Arch;
Wired up:
Raw Python test bed written:
from pynq import Overlay
ol = Overlay("LCD_Controller.bit")
# ================================
from pynq import GPIO
gpio_sendCommand = GPIO(GPIO.get_gpio_pin(0), 'out')
gpio_valid = GPIO(GPIO.get_gpio_pin(1), 'out')
gpio_ready = GPIO(GPIO.get_gpio_pin(2), 'in')
def isReady():
result = gpio_ready.read()
if result:
return True
return False
# ================================
from pynq import MMIO
databus_address = ol.ip_dict['axi_gpio_databus']['phys_addr']
RANGE = 4
databus = MMIO(databus_address, RANGE)
# ================================
def databus_write(data):
databus.write(0,data)
# ================================
# raw test set address
print(isReady())
gpio_valid.write(0)
gpio_sendCommand.write(1)
databus_write(0b1000)
gpio_valid.write(1)
print(isReady())
gpio_valid.write(0)
databus_write(0b0010)
gpio_valid.write(1)
gpio_valid.write(0)
gpio_sendCommand.write(0)
print(isReady())
# ================================
#raw test set character
print(isReady())
gpio_valid.write(0)
gpio_sendCommand.write(0)
databus_write(0b0100)
gpio_valid.write(1)
print(isReady())
gpio_valid.write(0)
databus_write(0b1000)
gpio_valid.write(1)
gpio_valid.write(0)
gpio_sendCommand.write(0)
print(isReady())
# ================================
The conversation happens, because the LCD driver sets the ready bit in its reply, each time I send 2 * 4 bits.
But the magic doesn't happen yet. No characters.
This was supposed to be my entry for the Project14 Build a Present. Like javagoza, I tried to make a device driver as present.
With the week-end finished, I guess that won't happen 
.
Some good news: it's not working, but it's trying:
This is a capture of the startup procedure. If you look at E, you can spot the 3 longer init sequences, then 1 burst to set 4 bit mode, then 2 * 6 4 bit bursts with the init settings.
The first thing I see, is that R/~W is high. It should be low while writing....
I found the reason for the failure of the R/~W:
I had set it to V12, pin 9 of PMODB. It should be W18, pin 9 of PMOD A:
checking:
That's better. I'll reconnect the LCD to the Pynq board and retry ...
Partly success:
It's not correct, I sent a single 'a'. But it's better than before.
Partly success:
It's not correct, I sent a single 'a'. But it's better than before.
Success.
I'm sending a stream of 'f'. I used f because that's binary '01100110',
so if I keep sending '0110' values, it should generate all 'f's. Yay!