DIY Electronics Projects and Tutorials: Arduino

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Monday, February 5, 2024

XC95108 VHDL Parallel to Serial Shift Registers and Arduino Example

A parallel to serial shift register is useful for microprocessor digital inputs extending. For instant a keypad input for printer for photocopier machine. There are many off-the-shelf parallel to serial shift register chips, especially the SN74HC165.

Hardware Testing

Using a programmable logic device we can design this kind of chip with customizable operations, and the numbers of I/O. This job could be done with a CPLD chip and its design tool, VHLD, Verilog code, or even schematic design tool.

Running Arduino Program and the XC95108

In this example, I use an XC95108 CPLD to design a parallel to serial converter chip. VHDL code is preferred for this design. This design contains,

Clock (CLK) input,
LOAD input to latch data from an 8-bit digital input to the internal register,
Serial Data Out (DOUT) that shift data serially at the rising edge of input clock,
Digital Input (D) is an 8-bit data input.

The overall process requires 9 clock cycles. At the first clock, data will be read and latched into an internal register, then the 8-bit serial data shifting out will be processed.

----------------------------------------------------------------------------------
-- Company: 
-- Engineer: 
-- 
-- Create Date:    08:31:41 02/03/2024 
-- Design Name: 
-- Module Name:    parallel_serial_2 - Behavioral 
-- Project Name: 
-- Target Devices: 
-- Tool versions: 
-- Description: 
--
-- Dependencies: 
--
-- Revision: 
-- Revision 0.01 - File Created
-- Additional Comments: 
--
----------------------------------------------------------------------------------
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
 
entity parallel_serial_2 is
    Port ( CLK : in  STD_LOGIC;
           LOAD : in  STD_LOGIC;
           DOUT : out  STD_LOGIC;
           D : in  STD_LOGIC_VECTOR (7 downto 0));
end parallel_serial_2;
 
architecture Behavioral of parallel_serial_2 is
	SIGNAL REG: STD_LOGIC_VECTOR(7 DOWNTO 0);
begin
	PROCESS(CLK,LOAD)
		BEGIN
			IF(CLK'EVENT AND CLK='1') THEN
				IF(LOAD='1') THEN REG<=D;
				ELSE REG<=REG(6 DOWNTO 0)&'0'; END IF;
			END IF;
	END PROCESS;
	DOUT<=REG(7);
end Behavioral;

You can use the FloorPlan I/O tool in the ISE Design Suite to assign its I/O pins. On the XC95108 CPLD Prototype Board, I set the I/O as follow.

#PACE: Start of Constraints generated by PACE
 
#PACE: Start of PACE I/O Pin Assignments
NET "CLK"  LOC = "P50"  ;
NET "D<0>"  LOC = "P48"  ;
NET "D<1>"  LOC = "P47"  ;
NET "D<2>"  LOC = "P46"  ;
NET "D<3>"  LOC = "P45"  ;
NET "D<4>"  LOC = "P44"  ;
NET "D<5>"  LOC = "P43"  ;
NET "D<6>"  LOC = "P41"  ;
NET "D<7>"  LOC = "P40"  ;
NET "DOUT"  LOC = "P52"  ;
NET "LOAD"  LOC = "P51"  ;
#PACE: Start of PACE Area Constraints
 
#PACE: Start of PACE Prohibit Constraints
 
#PACE: End of Constraints generated by PACE

The Arduino is very popular for most of electronics projects. I use an Arduino Uno to read the data from this chip.

 
 
const char clockPin= 13;
const char Enable = 10;
const char dataPin=12;
 
uint8_t incoming=0,oldData;
 
void setup() {
  Serial.begin(9600);
  Serial.println("Arduino ShiftIn And XC95108 Parallel To Serial Converter.");
  pinMode(clockPin,OUTPUT);
  pinMode(Enable,OUTPUT);
  pinMode(dataPin,INPUT);
  digitalWrite(clockPin,LOW);
  digitalWrite(Enable,LOW);
}
 
void loop() {
  digitalWrite(Enable,HIGH);
  digitalWrite(clockPin,LOW);
  digitalWrite(clockPin,HIGH);
  digitalWrite(Enable,LOW);
 
  for(uint8_t i=0;i<8;i++){
    digitalWrite(clockPin,LOW);
    if(digitalRead(dataPin)==1) incoming|=(1<<(7-i));
    else incoming&=~(1<<(7-i));   
    digitalWrite(clockPin,HIGH);
  }
  if(incoming!=oldData){
    Serial.println("Received 8-Bit HEX Data: 0x" + String(incoming,HEX));
    Serial.println("Received 8-Bit BIN Data: 0b" + String(incoming,BIN));
    oldData=incoming;
  }
  // Serial.println(incoming,HEX);
  //Serial.println(incoming,BIN);
  delay(1500);
}

Click here to download this example.

Monday, January 29, 2024

XC95108 Two-Digit 7-Segment Shift Registers VHDL Example

In previous post, I use the XC95108 to make a 16-bit LED shift registers. It's similar to the SNHC164 serial in parallel out shift registers chip. Using a CPLD and VHDL code we can customize any digital circuit.

The Arduino Uno and the XC95108 CPLD Prototype Board

Here I make another serial in parallel out shift registers chip that's similar to the SN74HC595. It's a two-digit 7-Segment display driver with SPI interface. It has the following I/O:

Reset (RST) input (active low)
Enable (EN) input for data latching
Serial Data In (MOSI)
Serial Clock In (SCK)
7-Segment Digit 1 (LEDA)
and 7-Segment Digit 2 (LEDB).

The 7-Segment display is a two-digit 0.56" red common cathode display. The shift registers process is synchronize with the logic high level of serial clock input (SCK). Shift registers data are latched into the output LED ports at the high to low transition of the EN (Enable) pin.

----------------------------------------------------------------------------------
-- Company: 
-- Engineer: 
-- 
-- Create Date:    08:29:52 01/30/2024 
-- Design Name: 
-- Module Name:    spi_7_2 - Behavioral 
-- Project Name: 
-- Target Devices: 
-- Tool versions: 
-- Description: 
--
-- 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 primitives in this code.
--library UNISIM;
--use UNISIM.VComponents.all;
 
entity spi_7_2 is
    Port ( RST : in  STD_LOGIC;
           EN : in  STD_LOGIC;
           SCK : in  STD_LOGIC;
           MISO : in  STD_LOGIC;
           LEDA : out  STD_LOGIC_VECTOR (7 downto 0);
           LEDB : out  STD_LOGIC_VECTOR (7 downto 0));
end spi_7_2;
 
architecture Behavioral of spi_7_2 is
	SIGNAL REGA,REGB: STD_LOGIC_VECTOR(7 DOWNTO 0);
begin
PROCESS(SCK,RST,EN)
	BEGIN
		IF(RST='0') THEN REGA<=x"00"; REGB<=x"00";
		ELSIF(SCK'EVENT AND SCK='1') THEN
			-- REGISTER A
			REGA(0)<=MISO;
			REGA(1)<=REGA(0);
			REGA(2)<=REGA(1);
			REGA(3)<=REGA(2);
			REGA(4)<=REGA(3);
			REGA(5)<=REGA(4);
			REGA(6)<=REGA(5);
			REGA(7)<=REGA(6);
 
			-- REGISTER B
			REGB(0)<=REGA(7);
			REGB(1)<=REGB(0);
			REGB(2)<=REGB(1);
			REGB(3)<=REGB(2);
			REGB(4)<=REGB(3);
			REGB(5)<=REGB(4);
			REGB(6)<=REGB(5);
			REGB(7)<=REGB(6);
 
		END IF;
		-- INPUT DATA LATCH
		IF(EN'EVENT AND EN='1') THEN
		LEDA<=REGA; LEDB<=REGB;
		END IF;
END PROCESS;
 
end Behavioral;

This VHDL circuit design uses 32 macro cells and 27 function blocks.

XC95108 CPLD Reports

I connect the CPLD to its on-board I/O devices (user constraint file) as follow.

#PACE: Start of Constraints generated by PACE
 
#PACE: Start of PACE I/O Pin Assignments
NET "EN"  LOC = "P54"  ;
NET "LEDA<0>"  LOC = "P23"  ;
NET "LEDA<1>"  LOC = "P24"  ;
NET "LEDA<2>"  LOC = "P36"  ;
NET "LEDA<3>"  LOC = "P34"  ;
NET "LEDA<4>"  LOC = "P33"  ;
NET "LEDA<5>"  LOC = "P21"  ;
NET "LEDA<6>"  LOC = "P35"  ;
NET "LEDA<7>"  LOC = "P37"  ;
NET "LEDB<0>"  LOC = "P19"  ;
NET "LEDB<1>"  LOC = "P20"  ;
NET "LEDB<2>"  LOC = "P31"  ;
NET "LEDB<3>"  LOC = "P25"  ;
NET "LEDB<4>"  LOC = "P26"  ;
NET "LEDB<5>"  LOC = "P17"  ;
NET "LEDB<6>"  LOC = "P18"  ;
NET "LEDB<7>"  LOC = "P32"  ;
NET "MISO"  LOC = "P53"  ;
NET "RST"  LOC = "P50"  ;
NET "SCK"  LOC = "P52"  ;
 
#PACE: Start of PACE Area Constraints
 
#PACE: Start of PACE Prohibit Constraints
 
#PACE: End of Constraints generated by PACE

Using the Arduino Uno is common for most of electronics hobbyists. I use the Arduino SPI to send 7-Segment data to the XC95108 CPLD Prototype Board. This program will count up and down between 0 and 99.

#include <SPI.h>
 
const char data_7[]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F};
const char EN=10;
volatile char data[2];
volatile char count=0,up_down=0;
 
void setup() {
  SPI.begin();
  pinMode(EN,OUTPUT);
  digitalWrite(EN,LOW);
}
 
void loop() {
  data[1]=data_7[count%10];  
  data[0]=data_7[count/10];
  SPI.transfer(data,2);
  digitalWrite(EN,HIGH);
  delay(1);
  digitalWrite(EN,LOW);
  if(count==99) up_down=1;
  else if(count==0) up_down=0;
  if(up_down==1) count--;
  else if(up_down==0) count++;
  delay(250);
}

The Arduino Uno must connects to the CPLD as follow.

Arduino Uno GND -> XC95108 CPLD GND
Arduino Uno SCK (PIN13) -> XC95108 CPLD (P52)
Arduino Uno MOSI (PIN11) -> XC95108 CPLD (P53)
Arduino Uno EN (PIN10) -> XC95108 CPLD (P54)

Click here to download its source file.

Friday, December 15, 2023

XC9536 SPI Two-Digit Multiplexing Display Driver

In this VHDL example, I design a Serial Peripheral Interface (SPI) receiver circuit that can drive a two-digit multiplexing display. The SPI receiver module is similar to a SN74HC164 serial-in-parallel-out shift registers. This module contains two shift registers inside. These two registers connects individually connect to two output port that drive to a two-digit multiplexing display.

I an Arduino Uno to send a serial data package over the SPI to the XC9536 CPLD on board.

SPI module does not need internal clock source. But the multiplexing display module needs a clock source to drive its output display at a rate of 16 milliseconds. I use an NE555 square wave oscillator to create a timing signal with a frequency of 60Hz for multiplexing display driving.

This design contains two process one's for SPI receiver module, and another one's for multiplexing display driving. These two processes are concurrent so the multiplexing display process does not need to wait or get interrupted by the SPI receiving process.

----------------------------------------------------------------------------------
-- Company: 
-- Engineer: 
-- 
-- Create Date:    08:34:17 12/15/2023 
-- Design Name: 
-- Module Name:    spi_display_2 - Behavioral 
-- Project Name: 
-- Target Devices: 
-- Tool versions: 
-- Description: 
--
-- 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 primitives in this code.
--library UNISIM;
--use UNISIM.VComponents.all;
 
entity spi_display_2 is
    Port ( OSC : in  STD_LOGIC;
           RST : in  STD_LOGIC;
		   TEST:  in  STD_LOGIC;
           SCLK : in  STD_LOGIC;
           SDAT : in  STD_LOGIC;
           COM : out  STD_LOGIC_VECTOR (1 downto 0);
           LED : out  STD_LOGIC_VECTOR (7 downto 0));
end spi_display_2;
 
architecture Behavioral of spi_display_2 is
	signal reg_0,reg_1 : STD_LOGIC_VECTOR(7 DOWNTO 0):=x"00";
 
begin
-- SPI Receiver Block
spi_receive: process(SCLK,RST)
	begin
		if(RST='0') then		
			reg_0<=x"00"; reg_1<=x"00";
		elsif(SCLK'EVENT AND SCLK='1') then
		-- Serial Data Receive
			reg_0(0)<=SDAT;
			reg_0(1)<=reg_0(0);
			reg_0(2)<=reg_0(1);
			reg_0(3)<=reg_0(2);
			reg_0(4)<=reg_0(3);
			reg_0(5)<=reg_0(4);
			reg_0(6)<=reg_0(5);
			reg_0(7)<=reg_0(6);
 
			reg_1(0)<=reg_0(7);
			reg_1(1)<=reg_1(0);
			reg_1(2)<=reg_1(1);
			reg_1(3)<=reg_1(2);
			reg_1(4)<=reg_1(3);
			reg_1(5)<=reg_1(4);
			reg_1(6)<=reg_1(5);
			reg_1(7)<=reg_1(6);
 
		end if;	
 
end process spi_receive;
 
-- Multiplexing Display Block
display_multiplex: process(OSC,RST)
	variable ticks : INTEGER RANGE 0 TO 1:=0;
	begin
		if(RST='0') then ticks:=0; COM<="00"; LED<=x"00";
		elsif(OSC'EVENT AND OSC='1') then
			ticks:=ticks+1;
			if(test='1') then
				CASE ticks IS
					WHEN 0	=> LED<=reg_0; COM<="01";
					WHEN 1	=> LED<=reg_1; COM<="10";					
					WHEN OTHERS => NULL;
				END CASE;
			else
				CASE ticks IS
					WHEN 0	=> LED<=x"3F"; COM<="01";
					WHEN 1	=> LED<=x"06"; COM<="10";				
					WHEN OTHERS	=> NULL;
				END CASE;
			end if;
		end if;
end process display_multiplex;
end Behavioral;

As we can see the display has three digits but I can use only two digits because the XC9536 CPLD has limited resource. I can not add one more shift registers signal.

I assign all of its I/O pins as follow.

Xilinx PACE

Its user constraints file is automatically generated after the Xilinx PACE is saved.

#PACE: Start of Constraints generated by PACE
#PACE: Start of PACE I/O Pin Assignments
NET "COM<0>" LOC = "P42" ;
NET "COM<1>" LOC = "P43" ;
NET "LED<0>" LOC = "P33" ;
NET "LED<1>" LOC = "P34" ;
NET "LED<2>" LOC = "P35" ;
NET "LED<3>" LOC = "P36" ;
NET "LED<4>" LOC = "P37" ;
NET "LED<5>" LOC = "P38" ;
NET "LED<6>" LOC = "P39" ;
NET "LED<7>" LOC = "P40" ;
NET "OSC" LOC = "P5" ;
NET "RST" LOC = "P25" ;
NET "SCLK" LOC = "P18" ;
NET "SDAT" LOC = "P19" ;
NET "TEST" LOC = "P26" ;
#PACE: Start of PACE Area Constraints
#PACE: Start of PACE Prohibit Constraints
#PACE: End of Constraints generated by PACE

I still use a Xilinx Parallel Cable III to program this CPLD.

Xilinx iMPACT Tools

We don't need to press the SPI serial data and serial clock manually. We just use an Arduino Uno board to send SPI data to this board. The Arduino uses three pins, MOSI, SCK, and reset to connect to the CPLD.

The Arduino program below sends a counting variable ranging from 0 to 99 to the CPLD.

#include<SPI.h>
 
void setup() {
  SPI.begin();
  pinMode(10,OUTPUT);
  digitalWrite(10,LOW);
  delay(1);
  digitalWrite(10,HIGH);
  SPI.transfer(0x3F);
  SPI.transfer(0x3F);
  delay(2500);
}
 
int count=0;
const char _7_SEG[10]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F,};
void loop() {
    SPI.transfer(_7_SEG[count%10]);
    SPI.transfer(_7_SEG[count/10]);
    delay(250);
    count++;
    if(count>99) count=0;
 
}

This program sends a random decimal number between 0 and 99 to the CPLD board.

#include<SPI.h>
 
void setup() {
  SPI.begin();
  pinMode(10,OUTPUT);
  digitalWrite(10,LOW);
  delay(1);
  digitalWrite(10,HIGH);
  SPI.transfer(0x3F);
  SPI.transfer(0x3F);
  delay(2500);
}
 
int myNumbers;
const char _7_SEG[10]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F,};
void loop() {
    myNumbers=random(99);
    SPI.transfer(_7_SEG[myNumbers%10]);
    SPI.transfer(_7_SEG[myNumbers/10]);
    delay(500);
}

Click here to download its source file.

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Monday, February 5, 2024

XC95108 VHDL Parallel to Serial Shift Registers and Arduino Example

Monday, January 29, 2024

XC95108 Two-Digit 7-Segment Shift Registers VHDL Example

Friday, December 15, 2023

XC9536 SPI Two-Digit Multiplexing Display Driver

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Monday, February 5, 2024

XC95108 VHDL Parallel to Serial Shift Registers and Arduino Example

Monday, January 29, 2024

XC95108 Two-Digit 7-Segment Shift Registers VHDL Example

Friday, December 15, 2023

XC9536 SPI Two-Digit Multiplexing Display Driver

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