mmbasic_original:driving_lcd_with_i2c_interface
Driving LCD with i2c interface
This module is part of the original MMBasic library. It is reproduced here with kind permission of Hugh Buckle and Geoff Graham. Be aware it may reference functionality which has changed or is deprecated in the latest versions of MMBasic.
Nice project to drive a standard HD4478 based LCD from an I2C port expander.
I2CLCD.bas
'
' http://letsmakerobots.com/node/4240 provided PIcAxe code
'
' Maximite modifications by John Gerrard
'
' +---------------------------------------------------------------+
' | |
' | LCD DISPLAY Hitachi HD44780 Standard |
' | |
' | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 |
' +-+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+-+
' | | | | | | | | | | | | | | | |
' GND V+ CNT RS RW E D0 D1 D2 D3 D4 D5 D6 D7 LV+ LGND
' | | | | | | | | | | | | | | | |
' = +5 | | = | | | | |
' | +-+ | | | | | | |
' | < | | | | | | |
' | 4k7 ><+ +------------------+ | | | |
' | < | | | | | |
' +-----+ | | | | | |
' | | | | | |
' | | | | | |
' | | | | | |
' | | | | | |
' to Maximite I2C | | | | | |
' ^ ^ | | | | | |
' +3.3| | ++ | | | | |
' | | | | | | | | | | | |
' +-+---+---+---+---+---+---+---+-+ | | | |
' | V+ SDA SCD INT P7 P6 P5 P4| | | | |
' | | | | | |
' D PCF8574 port expander | | | | |
' | | | | | |
' | A0 A1 A2 P0 P1 P2 P3 GND| | | | |
' +-+---+---+---+---+---+---+---+-+ | | | |
' | | | | | | | | | | | |
' +---+---+ | | | +------------------------+
' | | | +------------------------+
' gnd | +------------------------+
' +------------------------+
'
'
I2CEN 100,100 ' Enable I2C
I2CAddr = &H20 ' this is the 8574 I2C address
' A2=A1=A0=0 <-> x100 000x
'Name 8574 bit LCD
'---- -------- ---
DB4 = 0 ' LCD Data Line 4 (pin 11)
DB5 = 1 ' LCD Data Line 5 (pin 12)
DB6 = 2 ' LCD Data Line 6 (pin 13)
DB7 = 3 ' LCD Data Line 7 (pin 14)
RS = 4 ' 0 = Command 1 = Data (pin 4)
' 5 free (to pin 15 for lcd bk light, for ex.)
' 6 free
E = 7 ' 0 = Idle 1 = Active (pin 6)
RSCMDmask = &B00000000 ' Select Command register
RSDATmask = &B00010000 ' Select Data register = High P4 on 8574
Emask = &B11100000 ' Enable = P7 on 8574
Dim CNT(6)
CNT(0) = &H33 ' %0011---- %0011---- 8-bit / 8-bit
CNT(1) = &H32 ' %0011---- %0010---- 8-bit / 4-bit
' Byte commands - To configure the LCD
'
' Display Format
' 4bit mode, 2 lines, 5x7
'
' 001LNF00
CNT(2) = &B00101000 ' %00101000
' L : 0 = 4-bit Mode 1 = 8-bit Mode
' N : 0 = 1 Line 1 = 2 Lines
' F : 0 = 5x7 Pixels 1 = N/A
'
' Setup Display
' Display ON, Cursor On, Cursor Steady
'
' 00001DCB
CNT(3) = &B00001100 ' %00001110
' D : 0 = Display Off 1 = Display On
' C : 0 = Cursor Off 1 = Cursor On
' B : 0 = Cursor Steady 1 = Cursor Flash
'
' Setup Cursor/Display
' Inc Cursor Cursor Move
'
' 000001IS
CNT(4) = &B00000110 ' %000001IS Cursor Move
' I : 0 = Dec Cursor 1 = Inc Cursor
' S : 0 = Cursor Move 1 = Display Shift
CNT(5) = &B00000001 ' Clear Screen
GoSub InitialiseLcd ' Initialise the LCD
Menu:
line1$ = "2x20 LCD Test" ' Add your text here
line2$ = "2nd Line" ' And here
Gosub Line1 ' or gosub LCD_Mainloop if you want clear the screen
' Add key press stuff here
Goto menu
' I2C LCD
LCD_Mainloop:
aByte = CNT(5) 'Clear Screen
GoSub SendCmdByte
Line1:
aByte = &B00000010 ' Put cursor at start of Line 1
GoSub SendCmdByte
For i = 1 To Len(Line1$)
aByte = Asc(Mid$(Line1$, i, 1))
GoSub SendDataByte
Next i
If line2$ = "" Then Return
EndIf
Line2:
aByte = &H80 Or &H40 ' Put cursor at start of Line 2
GoSub SendCmdByte
For i = 1 To Len(Line2$)
aByte = Asc(Mid$(Line2$, i, 1))
GoSub SendDataByte
Next i
Return
' INITIALIZE LCD
' -----------------------------------------------------------------
'
InitialiseLcd:
For index = 0 To 5
aByte = CNT(index)
GoSub SendInitCmdByte
Next
Return
' SEND INIT CMD BYTE - SEND CMD BYTE - SEND DATA BYTE
' -----------------------------------------------------------------
'
SendInitCmdByte:
SendCmdByte:
rsbit = RSCMDmask ' Send to Command register
SendDataByte:
'
' put MSB OUT 1st
'
temp = (aByte \ &B10000) Or rsbit
GoSub DirectSendCmd
'
' put LSB
'
temp = aByte And &H0F Or rsbit
rsbit = RSDATmask ' Send to Data register next
DirectSendCmd:
temp = temp Xor Emask ' E=1
I2CSEND i2caddr, 0, 1, temp ' send to 8574
Pause 2
temp = temp Xor Emask ' E=0
I2CSEND i2caddr, 0, 1, temp
Return
mmbasic_original/driving_lcd_with_i2c_interface.txt · Last modified: 2024/02/24 17:19 by gerry