Raspberry Pi Forums

Posted: **Sun Jan 26, 2014 9:00 pm**

print " Distance : %4.1f cm" % distance

Total of 4 characters with one decimal. The dots and the decimal are parts of the total.

Daniel

Posted: **Sun Jan 26, 2014 10:59 pm**

Maybe

print " Distance :%5.1f cm" % distance

will be more adequate since it will take care of values >99.9 cm also.

Screen display information is somewhat very restricted.

Daniel

Posted: **Tue Jan 28, 2014 6:31 am**

can you tell me how did You connect it to pi, how many resistors did You use and the whole script that You used?

I tried to use HC-SR04 but it was killing my RTC DS1307

Posted: **Tue Jan 28, 2014 11:59 am**

Yes I used them a lot . But this was 20 years ago.

it was TTL serial made by Seiko.

I should have one . I will try to find it! No sure if I still have it.

I do have a new one , 4x20. which you could choose the interface.

Daniel

Posted: **Wed Jan 29, 2014 6:31 am**

can I ask just for a simple HOW-TO?

Posted: **Wed Jan 29, 2014 11:51 am**

Which interface you like to use? I2C, SPI or TTL serial?

Daniel

Posted: **Wed Jan 29, 2014 1:02 pm**

I tried http://www.bytecreation.com/blog/2013/1 ... or-hc-sr04

Posted: **Thu Jan 30, 2014 4:11 am**

I didn't see any lcd display from the url you provide.

This is an example of LCD class I just did, (took me 1/2 hour to type) and of course 1 hour to debug and make the Test program.

There are 2 python files,

MyLCD.py which is a class to encapsulate the serial TTL at 9600 baud to communicate with the LCD display.
LCDTest.py which is the test code.

The physical layout is just GND, VCC and the TX, pin 8, to the serial IN of the display. The display is 5V but it works very well with the 3.3V signal.

The display is a Newhaven Display 4x20 which could be program in I2c,SPI and presently in TTL serial.
MyLCD.py

Code: Select all

pi@Pi2 ~ $ cat MyLCD.py
import time
import serial

class MyLCD():

    def __init__(self):
       self.ser = serial.Serial(port='/dev/ttyAMA0',baudrate=9600)

    def write(self,val):
       self.ser.write(val)

    def ClearScreen(self):
       self.ser.write('\xFE\x51')

    def DisplayOn(self):
       self.ser.write('\xFE\x41')

    def DisplayOff(self):
       self.ser.write('\xFE\x42')

    def SetCursor(self,val):
       self.ser.write('\xFE\x45')
       self.ser.write(chr(val))

    def CursorHome(self):
       self.ser.write('\xFE\x46')

    def UnderlineCursorOn(self):
       self.ser.write('\xFE\x47')

    def UnderlineCursorOff(self):
       self.ser.write('\xFE\x48')

    def MoveCursorLeft(self):
       self.ser.write('\xFE\x49')

    def MoveCursorRight(self):
       self.ser.write('\xFE\x4A')

    def BlinkingCursorOn(self):
       self.ser.write('\xFE\x4B')

    def BlinkingCursorOff(self):
       self.ser.write('\xFE\x4C')

    def Backspace(self):
       self.ser.write('\xFE\x4E')

    def SetContrast(self,val):
       self.ser.write('\xFe\x52')
       self.ser.write(chr(val))
   
    def SetBacklight(self,val):
       self.ser.write('\xFE\x53')
       self.ser.write(chr(val))

    def LoadCustomCharacter(self, customChar,  val):
       self.ser.write('\xFE\x54')
       self.ser.write(chr(customChar))
       Tlen = len(val)
       if Tlen>8:
         Tlen=8
       for i in range(Tlen):
         self.ser.write(chr(val[i]))
       for i in range(Tlen,8,1):
         self.ser.write(chr(0))

    def MoveDisplayLeft(self):
       self.ser.write('\xFE\x55')

    def MoveDisplayRight(self):
       self.ser.write('\xFE\x56')

    def ChangeBaudRate(self,val):
       self.ser.write('\xFE\x61')
       self.ser.write(chr(val))

    def ChangeI2CAddress(self,val):
       self.ser.write('\xFE\x42')
       self.ser.write(chr(val))

    def DisplayVersion(self):
       self.ser.write('\xFE\x70')

    def DisplayBaudRate(self):
       self.ser.write('\xFE\x71')

    def DisplayI2CAddress(self):
       self.ser.write('\xFE\x72')

and LCDTest.py

Code: Select all

pi@Pi2 ~ $ cat TestLCD.py 
import time
import MyLCD
import signal
import sys

ser = MyLCD.MyLCD()


def signal_handler(signal, frame):
   ser.ClearScreen()
   ser.ClearScreen()
   ser.write('Bye!')
   sys.exit(0)


def DisplayCounter(counter):
  #specify First Line position 8
   ser.SetCursor(8)
   ser.write('%-6dcycles' % (counter))


def DisplayTime():
   #sepcify third line position 5
   ser.SetCursor(0x19)
   ser.write(time.strftime("%H:%M:%S"))
     




#insert control-C handler

signal.signal(signal.SIGINT, signal_handler)

#display start message
ser.ClearScreen()
ser.DisplayOn()
ser.UnderlineCursorOff()
ser.write('LCD DISPLAY Test.')
#move to second line
ser.SetCursor(0x40)
ser.write('From Raspberry Pi')

#create a custom character
#just a horizontal line in middle of character

ser.LoadCustomCharacter(1,[0,0,0,0xff,0xff,0,0,0])

#move to third line
ser.SetCursor(0x14)

for i in range(20):
  ser.write(chr(1))



#move to fourth line
ser.SetCursor(0x54)
datestring = time.strftime("%d/%m/%y %H:%M:%S")
ser.write(datestring)

time.sleep(3.0);


ser.ClearScreen()

ser.write('Counter:')
ser.SetCursor(0x14)
ser.write('Time:')

counter = 0

while(True):
  DisplayCounter(counter)
  DisplayTime()
  counter=counter+1  
  time.sleep(0.5)

P.S. Be sure to disable the debug console on /dev/ttyAMA0 in /boot/cmdline.txt and disable the /dev/ttyAMA0 login in /etc/inittab (The last line).

Also change the group owner of /dev/ttyAMA0 to 'dialout' since 'pi' is part of this group

Code: Select all

sudo chown .dialout /dev/ttyAMA0

Have fun

Posted: **Thu Jan 30, 2014 12:25 pm**

that's right, I didn't use a display yet with hc-sr04
I will try your method and the display I have which is 16x2 HD44780 standard display

thank You

Posted: **Thu Jan 30, 2014 1:52 pm**

Looks like that this lcd display uses 4/ 8 bits bus. So you will need to add a function to write the data using gpio instead of serial.

This is the same type of lcd I was using 25 years ago with Z8, not Z80, and 8051 cpu. I don't I have one anymore.

Daniel

Posted: **Thu Jan 30, 2014 2:11 pm**

add a function?

Posted: **Thu Jan 30, 2014 6:01 pm**

Yes the code I gave you is for a serial interface.

The Hitachi LCD display use 4 or 8 bits bus.

Instead of using the serial port you will have to send one byte a a time using 8 GPIOs and one more for writing signal.

If you don't have too much GPIO left , you could use the SPI with a serial shift register like the 74hC595 with one of the available SPI chip select.

I Will see if I have one lcd display like this. But I don't think so.

Daniel

Posted: **Thu Jan 30, 2014 6:33 pm**

I found an old Densitron display using the same Hitachi I.C.

So we are in business if the display works. I do have some 74hc595.

Posted: **Thu Jan 30, 2014 8:39 pm**

I also have a TFT LCD 2,2" with touchscreen from waveshare connected to my DVK511 board but I can't make it work (the driver loads properly but no display)

still I don't know how to connect HC-SR04 and not crash RTC DS1307
do you use any RTC?

Posted: **Fri Jan 31, 2014 2:37 am**

Ok the Densitron was broken. ;-(

I do have another one, but not with me. So It will have to wait a couple of days.

This is a small schematic on how to connect the LCD with the raspberry PI.

I'm sure that someone already made a design like this one to connect this kind of lcd. It is the simplest thing to do.

Maybe do a search on LCD and hc595.

Daniel

Posted: **Fri Jan 31, 2014 6:16 am**

I was thinking about a direct connection to the RPi
now I see I need to buy HC595

Posted: **Sat Feb 01, 2014 2:22 am**

Try to use this from adafruit

http://learn.adafruit.com/drive-a-16x2- ... i?view=all

Daniel

Posted: **Sat Feb 01, 2014 4:12 am**

I bought a LCD2002A at the nearest electronic surplus.

I debug the code and now it is working with the SPI device using the 74HC595.

I just modify the adafruit example to implements the SPI+74HC595.

B.T.W. My previous posted schematic is ok.

LCD_H595.py

Code: Select all

#!/usr/bin/python

#
# based on code from lrvick and LiquidCrystal
# lrvic - https://github.com/lrvick/raspi-hd44780/blob/master/hd44780.py
# LiquidCrystal - https://github.com/arduino/Arduino/blob/master/libraries/LiquidCrystal/LiquidCrystal.cpp
#

# took from Adafruit github
#https://raw.github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code/master/Adafruit_CharLCD/Adafruit_CharLCD.py
#modify By Daniel Perron, January 31, 2014  to implement 74HC595 version using SPI

from time import sleep
import spidev


class LCD_H595():

    # commands
    LCD_CLEARDISPLAY 		= 0x01
    LCD_RETURNHOME 		= 0x02
    LCD_ENTRYMODESET 		= 0x04
    LCD_DISPLAYCONTROL 		= 0x08
    LCD_CURSORSHIFT 		= 0x10
    LCD_FUNCTIONSET 		= 0x20
    LCD_SETCGRAMADDR 		= 0x40
    LCD_SETDDRAMADDR 		= 0x80

    # flags for display entry mode
    LCD_ENTRYRIGHT 		= 0x00
    LCD_ENTRYLEFT 		= 0x02
    LCD_ENTRYSHIFTINCREMENT 	= 0x01
    LCD_ENTRYSHIFTDECREMENT 	= 0x00

    # flags for display on/off control
    LCD_DISPLAYON 		= 0x04
    LCD_DISPLAYOFF 		= 0x00
    LCD_CURSORON 		= 0x02
    LCD_CURSOROFF 		= 0x00
    LCD_BLINKON 		= 0x01
    LCD_BLINKOFF 		= 0x00

    # flags for display/cursor shift
    LCD_DISPLAYMOVE 		= 0x08
    LCD_CURSORMOVE 		= 0x00

    # flags for display/cursor shift
    LCD_DISPLAYMOVE 		= 0x08
    LCD_CURSORMOVE 		= 0x00
    LCD_MOVERIGHT 		= 0x04
    LCD_MOVELEFT 		= 0x00

    # flags for function set
    LCD_8BITMODE 		= 0x10
    LCD_4BITMODE 		= 0x00
    LCD_2LINE 			= 0x08
    LCD_1LINE 			= 0x00
    LCD_5x10DOTS 		= 0x04
    LCD_5x8DOTS 		= 0x00



    def __init__(self, pin_rs=22, pin_e=18,GPIO = None):
	# Emulate the old behavior of using RPi.GPIO if we haven't been given
	# an explicit GPIO interface to use
	if not GPIO:
	    import RPi.GPIO as GPIO
   	self.GPIO = GPIO
        self.pin_rs = pin_rs
        self.pin_e = pin_e

        self.GPIO.setmode(GPIO.BOARD)
        self.GPIO.setup(self.pin_e, GPIO.OUT)
        self.GPIO.setup(self.pin_rs, GPIO.OUT)


        self.spi = spidev.SpiDev()
        self.spi.open(0,0)

	self.write4bits(0x38) # initialization
	self.write4bits(0x0E) # initialization
	self.write4bits(0x06) # 2 line 5x7 matrix
	self.write4bits(0x0C) # turn cursor off 0x0E to enable cursor
	self.write4bits(0x06) # shift cursor right

	self.displaycontrol = self.LCD_DISPLAYON | self.LCD_CURSOROFF | self.LCD_BLINKOFF

	self.displayfunction = self.LCD_8BITMODE | self.LCD_2LINE | self.LCD_5x8DOTS

	""" Initialize to default text direction (for romance languages) """
	self.displaymode =  self.LCD_ENTRYLEFT | self.LCD_ENTRYSHIFTDECREMENT
	self.write4bits(self.LCD_ENTRYMODESET | self.displaymode) #  set the entry mode

        self.clear()


    def begin(self, cols, lines):

	if (lines > 1):
		self.numlines = lines
    		self.displayfunction |= self.LCD_2LINE
		self.currline = 0


    def home(self):

	self.write4bits(self.LCD_RETURNHOME) # set cursor position to zero
	self.delayMicroseconds(3000) # this command takes a long time!
	

    def clear(self):

	self.write4bits(self.LCD_CLEARDISPLAY) # command to clear display
	self.delayMicroseconds(3000)	# 3000 microsecond sleep, clearing the display takes a long time


    def setCursor(self, col, row):

	self.row_offsets = [ 0x00, 0x40, 0x14, 0x54 ]

	if ( row > self.numlines ): 
		row = self.numlines - 1 # we count rows starting w/0

	self.write4bits(self.LCD_SETDDRAMADDR | (col + self.row_offsets[row]))


    def noDisplay(self): 
	""" Turn the display off (quickly) """

	self.displaycontrol &= ~self.LCD_DISPLAYON
	self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)


    def display(self):
	""" Turn the display on (quickly) """

	self.displaycontrol |= self.LCD_DISPLAYON
	self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)


    def noCursor(self):
	""" Turns the underline cursor on/off """

	self.displaycontrol &= ~self.LCD_CURSORON
	self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)


    def cursor(self):
	""" Cursor On """

	self.displaycontrol |= self.LCD_CURSORON
	self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)


    def noBlink(self):
	""" Turn on and off the blinking cursor """

	self.displaycontrol &= ~self.LCD_BLINKON
	self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)


    def noBlink(self):
	""" Turn on and off the blinking cursor """

	self.displaycontrol &= ~self.LCD_BLINKON
	self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)


    def DisplayLeft(self):
	""" These commands scroll the display without changing the RAM """

	self.write4bits(self.LCD_CURSORSHIFT | self.LCD_DISPLAYMOVE | self.LCD_MOVELEFT)


    def scrollDisplayRight(self):
	""" These commands scroll the display without changing the RAM """

	self.write4bits(self.LCD_CURSORSHIFT | self.LCD_DISPLAYMOVE | self.LCD_MOVERIGHT);


    def leftToRight(self):
	""" This is for text that flows Left to Right """

	self.displaymode |= self.LCD_ENTRYLEFT
	self.write4bits(self.LCD_ENTRYMODESET | self.displaymode);


    def rightToLeft(self):
	""" This is for text that flows Right to Left """
	self.displaymode &= ~self.LCD_ENTRYLEFT
	self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)


    def autoscroll(self):
	""" This will 'right justify' text from the cursor """

	self.displaymode |= self.LCD_ENTRYSHIFTINCREMENT
	self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)


    def noAutoscroll(self): 
	""" This will 'left justify' text from the cursor """

	self.displaymode &= ~self.LCD_ENTRYSHIFTINCREMENT
	self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)


    def WriteByte(self, val, char_mode=False):
	self.delayMicroseconds(50) # 50 microsecond sleep
        self.GPIO.output(self.pin_rs, char_mode)
        self.spi.xfer([val])
        self.pulseEnable();
        if not char_mode:
	   self.delayMicroseconds(2000) #command ? then  2000 microsecond sleep

           

    def write4bits(self, bits, char_mode=False):
        self.WriteByte(bits,char_mode)

    def delayMicroseconds(self, microseconds):
	seconds = microseconds / float(1000000)	# divide microseconds by 1 million for seconds
	sleep(seconds)

    def pulseEnable(self):
	self.GPIO.output(self.pin_e, False)
	self.delayMicroseconds(1)		# 1 microsecond pause - enable pulse must be > 450ns 
	self.GPIO.output(self.pin_e, True)
	self.delayMicroseconds(1)		# 1 microsecond pause - enable pulse must be > 450ns 
	self.GPIO.output(self.pin_e, False)
	self.delayMicroseconds(1)		# commands need > 37us to settle


    def message(self, text):
        """ Send string to LCD. Newline wraps to second line"""

        for char in text:
            if char == '\n':
                self.write4bits(0xC0) # next line
            else:
                self.write4bits(ord(char),True)


if __name__ == '__main__':

    lcd = LCD_H595()

    lcd.clear()
    lcd.message("  LCD 16x2\n  SPI + 74HC595")

Posted: **Sat Feb 01, 2014 10:19 am**

I do have the 16x2 display that was described in adafruit's article

but I also have the DVK511 board from waveshare and the 2,2" TFT LCD display with touchscreen dedicated to that board
I'm just a noob at programming

Posted: **Sat Feb 01, 2014 1:09 pm**

Is this display use SPI ? looks like it. Than it is way easier.

And since you have that interface board , you don't need that hc595.

But the python code will be way different from the Adafruit or my TTL serial .

Check http://projects.pithan.net/lcd-touch-module/

In the touch screen category, I prefer to use more intelligent display. product like

http://www.4dsystems.com.au/product/5/3 ... _43_PT_PI/

With this system, it is possible that you won't need a raspberry Pi at all. Just the display will do.

Daniel

Posted: **Sun Feb 02, 2014 1:25 pm**

the link you gave is for that display that I have with my RPi&DVK511
but it doesn't work for me

Posted: **Sun Feb 02, 2014 1:36 pm**

I don't have your board and your display.

But first go step by step.

1 - Just use the Rpi and the display first. Don't use your add-on board.
2 - Check the display first. and after check the touch screen.

If you plug everything and hope that everything will works. It won't.

Daniel

Posted: **Sun Feb 02, 2014 2:13 pm**

the image given with the DVK511 board shows that the display is ok

Posted: **Sun Feb 02, 2014 2:22 pm**

Well an image is an image,

You have to do the works. So start small and add little by little.

Daniel

Posted: **Sun Feb 02, 2014 2:40 pm**

okay...

I found some wires and connected the display directly to RPi pins as You suggested
doesn't work

it only lights when I turne the power on...

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