' -----------------------------------------------------------
' Routines for Micromite to drive serial I2C LCD
' by Andy H. 17/05/2017
' Adapted from a program by Jim Rowe.
' 3 calls in total
' initLCD - Initialises the LCD Controller
' ClearScreen - Clears the display and sets cursor to line 1 position 1
' DisplayText row, offset, text$ - which row to output on, repositions cursor to offset, txt to be displayed


' LCD functions of PCF8571 output bits P0 - P7:
' Name 8574 bit LCD function
' DB4 = P4 Data Line 4 (pin 11)
' DB5 = P5 Data Line 5 (pin 12)
' DB6 = P6 Data Line 6 (pin 13)
' DB7 = P7 Data Line 7 (pin 14)
' RS = P0 Reg select (pin 4) 0 = Cmd 1 = Data
' EN = P2 EN (pin 6) 0 = Idle, 1 = Active
' R/Wbar = P1 R/W-bar (pin 5, should be 0 for writing)
' BL = P3 Backlight control (Q1 & LCD pin 16)
' ----------------------------------------------------------

OPTION AUTORUN ON
OPTION EXPLICIT
option default integer

' declare the PCF8574 I2C address (all links out)
DIM AS LCDI2CAddr = &H27 ' (A2=A1=A0=1)

' masks for preparing I2C bytes for writing to 8574 & LCD
DIM RSCmask = &B00000000 ' select cmd register (RS = 0)
DIM RSDmask = &B00000001 ' or data register (RS = 1)
DIM ENmask = &B00000100 ' Enable (active = P2 high)
DIM BLmask = &B00001000 ' Turn on backlighting (P3 = 1)
Dim CNT(7) ' array to store LCD config command bytes
CNT(0) = &B00110011 ' &H33 --> 8-bit / 8-bit mode init
CNT(1) = &B00110010 ' &H32 --> 8-bit / 4-bit mode
CNT(2) = &B00101000 ' &H28 --> 4-bit mode, 2 lines, 5x7 pixels
CNT(3) = &B00001000 ' &H08 --> disp off, cursor off, no blink
CNT(4) = &B00000001 ' &H01 --> clear screen, return home cmd
CNT(5) = &B00000110 ' &H06 --> increment cursor, cursor move
CNT(6) = &B00001100 ' &H0C --> disp on, cursor off, no blink
dim line1home = &B10000000 ' &H80 --> Place cursor at start of line 1
Dim line2home = &B11000000 ' &HC0 Place cursor at start of line 2

PAUSE 200 ' wait 200ms for LCD to stabilise after powerup
I2C OPEN 100,100 ' enable I2C (bus speed 100kHz, 100ms timeout)
InitLCD ' then go initialise the LCD + controller

' main program loop starts here
DO
ClearScreen
DisplayText 1, 0, "1234567890"
DisplayText 2, 10, "GoodToGo!!"
DisplayText 3, 0, "abcdefghij"
DisplayText 4, 10, "zyxwvutsrq"
PAUSE 1000
DisplayText 1, 10, "1234567890"
DisplayText 2, 0, "GoodToGo!!"
DisplayText 3, 10, "abcdefghij"
DisplayText 4, 0, "zyxwvutsrq"
pause 1000
LOOP

END ' end of main part of program, subs follow

' -----------------------------------------------------------------

' subroutine to Display text on LCD.
sub DisplayText row, offset, text$
local i
select case row
case 1
sendcmdbyte (line1home + offset)
case 2
sendcmdbyte line2home + offset)
case 3
sendcmdbyte (line1home + 20 + offset)
case 4
sendcmdbyte (line2home + 20 + offset)
end select
For i = 1 To Len(text$)
SendDataByte ASC(Mid$(text$, i, 1))
Next i
end sub

' -----------------------------------------------------------------

' subroutine to clear LCD screen
sub ClearScreen
SendCmdByte cnt(4)
PAUSE 400 ' pause for 400ms to give it time...
end sub

' -----------------------------------------------------------------

' subroutine to initialise the LCD
SUB InitLCD
local i
For i = 0 To 6
SendCmdByte cnt(i)
IF i = 4 THEN
PAUSE 20 ' pause for 20ms to allow full clear
END IF
PAUSE 50 ' pause to let LCD controller settle down
Next
END SUB

' -----------------------------------------------------------------

' subroutine to send a command byte (aByte) to the LCD controller
SUB SendCmdByte aByte
local temp, RSbit
RSbit = RSCmask ' make sure we're sending to cmd reg (RS=0)
' then prepare the more significant nibble
temp = (aByte AND &HF0) Or RSbit OR BLmask
DirectSend temp ' and send it
' then prepare the less significant nibble
temp = ((aByte AND &H0F) << 4) Or RSbit OR BLmask
DirectSend temp ' and send it also
END SUB

' -----------------------------------------------------------------

' subroutine to send a data byte (aByte) to the LCD controller
SUB SendDataByte aByte
local temp, RSbit
RSbit = RSDmask ' make sure we're sending to data reg (RS=1)
' then prepare the more significant nibble (from aByte)
temp = (aByte AND &B01110000) Or RSbit OR BLmask
DirectSend temp ' and send it
' then prepare the less significant nibble (from aByte)
temp = ((aByte AND &H0F) << 4) OR RSbit OR BLmask
DirectSend temp ' and send it also
END SUB

' -----------------------------------------------------------------

' subroutine to send a nibble (in temp) to the LCD
SUB DirectSend temp
temp = temp Xor ENmask ' make EN=1
I2C WRITE LCDI2CAddr, 0, 1, temp ' send it with EN=1
Pause 10 ' pause for 10ms
temp = temp Xor ENmask ' now make EN=0 again
I2C WRITE LCDI2CAddr, 0, 1, temp ' before sending again
END SUB
' ----------------------------------------------------------------