;Procedure to wait for the last I2C operation to complete.

;Code polls the SSPIF flag in PIR1.

WaitI2C

15.2 Sample Programs

The following sections contain the code listing for the programs discussed in this chapter.

15.2.1 EECounter Program

;File name: EECounter.asm

;Last Update: May 22, 2006

;Author: Julio Sanchez

;Processor: 16F84A

;Description:

;Program to demonstrate on chip EEPROM data memory read

;and write operation. Program uses LCD display to output

;results.

;Operation:

;The program keeps track and displays the inNum of times

;the code has been started.

;For LCD display parameters see the LCDTest2 program.

;WARNING:

;Code assumes 4Mhz clock. Delay routines must be

;edited for faster clock

;

;===========================

;switches ;===========================

;Switches used in __config directive:

;_PWRTE_OFF

;|

;|_____ * indicates setup values presently selected

;=========================

;Note: The constants that define the LCD display line

;addresses have the high-order bit set in

;order to facilitate the controller command

;

;===================================================== ; variables in PIC RAM ;=====================================================

;Reserve 16 bytes for string buffer cblock 0x0c

strData endc

;Reserve three bytes for ASCII digits cblock 0x1d

asc100

asc10

asc1 endc

;Continue with local variables

cblock 0x20 count1 count2 count3

;first LCD line ;======================

;Store 16 blanks in PIC RAM, starting at address stored

;Call procedure to store ASCII characters for message

;in text buffer

call storeMS1

;=======================

;Read EEPROM memory ;=======================

;EEPROM memory address to use is at 10 (0x0a). Variable

;EEMemAdd is already initialized.

;Fill data for EEPROM is 0xff. This value indicates

;the first iteration

; EEPROM data still in w

incf EEByte,f

call EEWrite

;At this point iteration inNum is stored in EEByte

;This value must be displayed on the LCD at offset 11

;of the first line. This means it must be stored at offset

;11 in the buffer. Since the buffer starts at 0x0c the

;iteration digit must be stored at offset 0x0c+11=0x17 ShowEEData:

;Binary data in EEByte

;At this point three ASCII digits are stored in local

;variables. Move digits to display area

;Display line

;Set DDRAM address to start of first line showLine:

call line1

; Call procedure to display 16 characters in LCD call display16

loopHere:

goto loopHere ;done

;============================================================ ; initialize LCD for 4-bit mode ;============================================================ initLCD:

;Initialization for Densitron LCD module as follows:

;4-bit interface

;2 display lines of 16 characters each

;cursor on

;left-to-right increment

;cursor shift right

;no display shift

return

;=======================

;Procedure to delay

;42 microseconds ;======================= delay_125

;=======================

;Procedure to delay

;5 milliseconds ;======================= delay_5

;=============================

;long delay sub-routine

;(for debugging) ;============================= long_delay

goto jloop

return

;=============================

;LCD display procedure ;=============================

;Sends 16 characters from PIC buffer with address stored

;in variable pic_ad to LCD line previously selected display16

;========================

;send 2 nibbles in

;4-bit mode ;========================

;Procedure to send two 4-bit values to Port-B lines

;7, 6, 5, and 4. High-order nibble is sent first

;ON ENTRY:

;w register holds 8-bit value to send

send8:

;=================

;merge bits ;=================

;Routine to merge the 4 high-order bits of the

;value to send with the contents of Port-B

;so as to preserve the 4 low-bits in Port-B

;Logic:

;AND value with 1111 0000 mask

;AND Port-B with 0000 1111 mask

;Now low nibble in value and high nibble in

;Port-B are all 0 bits:

;value = vvvv 0000

;Port-B = 0000 bbbb

;OR value and Port-B resulting in:

;ON ENTRY:

;w contains value bits

;ON EXIT:

;w contains merged bits

merge4:

;========================

;blank buffer ;========================

;Procedure to store 16 blank characters in PIC RAM

;buffer starting at address stored in the variable

;pic_ad

blank16

storeit

;ASSERT: valid string character in w

;store character in text buffer (by FSR)

;Routine for returning message stored in program area

;Message has 10 characters

msg1:

;==============================

;binary to ASCII decimal

;conversion ;==============================

;ON ENTRY:

;w register has binary value in range 0 to 255

;ON EXIT:

;output variables asc100, asc10, and asc1 have

;three ASCII decimal digits

;Routine logic:

;The value 100 is subtracted from the source operand

;until the remainder is < 0 (carry cleared). The number

;of subtractions is the decimal hundreds result. 100 is

;then added back to the subtrahend to compensate

;for the last subtraction. Now 10 is subracted in the

;same manner to determine the decimal tenths result.

;The final remainder is the decimal units result.

;Variables:

;asc100 storage for hundreds position result

;============================================================ ; EEPROM procedures ;============================================================ ;==============================

;read EEPROM ;==============================

;Procedure to read EEPROM memory. Address of memory

;location to read is stored in local register EEMemAdd

;On exit: read data in w

EERead:

;==============================

;write EEPROM ;==============================

;Procedure to write asc1 byte to EEPROM memory

;Address to write stored in local register EEMemAdd

;Data byte to write is in local register EEByte EEWrite:

;Load byte to write into EE data register

End

15.2.2 Ser2EEP Program

;File name: Ser2EEP.asm

;Last revision: May 26, 2006

;Author: Julio Sanchez

;PIC: 16F877

;Description:

;Receive character data through RS-232 line and store in

;EEPROM data memory. Received characters are echoed on

;the second LCD line. When <Enter> key is detected (code

;0x0d) the text stored in EEPROM memory is retrieved and

;displayed on the LCD. On startup the top LCD line displays

;the prompt: “Receiving:”. At that time a message “Rdy- ” is

;sent through the serial line so as to test the connection.

;Default serial line setting:

;Program to use 4-bit PIC-to-LCD interface.

;Code assumes that LCD is driven by Hitachi HD44780

;controller and PIC 16F977. Display supports two lines

;each one with 20 characters. The length, wiring and base

;address of each display line is stored in #define

;statements. These statements can be edited to accommodate

;a different set-up.

; for PIC-to-LCD pin wiring and LCD line addresses ;=====================================================

#define LCDlimit .20; Number of characters per line #define spbrgVal .64; For 2400 baud on 10Mhz clock

;Note: The constants that define the LCD display

;line addresses have the high-order bit set

;so as to meet the requirements of controller

;commands.

;

;========================================================== ; General Purpose Variables ;==========================================================

;Local variables

;Reserve 20 bytes for string buffer cblock 0x20

strData endc

;Other data

;==============================

;Common RAM area ;==============================

;These GPRs can be accessed from any bank.

;15 bytes are available, from 0x70 to 0x7f

cblock 0x70

; For LCDscroll procedure

LCDcount ; Counter for characters per line

; EEPROM-related variables

EEMemAdd ; EEPROM address to access

;============================================================

; P R O G R A M

;============================================================

;Wiring:

;LCD data to Port-D, lines 0 to 7

;E line -> Port-E, 1

;RW line -> Port-E, 2

;RS line -> Port-E, 0

;Set PORTE D and E for output

;First, initialize Port-B by clearing latches clrf STATUS

clrf PORTB

;Select bank 1 to TRIS Port-D for output Bank1

;TRIS Port-D for output. Port-D lines 4 to 7 are wired

;to LCD data lines. Port-D lines 0 to 4 are wired to LEDs. movlw B’00000000’

;By default Port-A lines are analog. To configure them

;as digital code must set bits 1 and 2 of the ADCON1

;register (in bank 1)

; make all Port-A lines digital

movwf ADCON1

;Port-B, lines are wired to keypad switches, as follows:

;7 6 5 4 3 2 1 0

;| | | | |_|_|_|_____ switch rows (output)

;|_|_|_|_____________ switch columns (input)

;rows must be defined as output and columns as input

; Enable Port-B pullups for switches in OPTION register movlw b’00001000’

movwf OPTION_REG

;Back to bank 0 Bank0

;Initialize serial Port-for 2400 baud, 8 bits, no parity

;1 stop

; Clear character counter and line counter variables

;============================================================

;receive serial data, store, and display ;============================================================ receive:

;Call serial receive procedure

call SerialRcv

;HOB of newData register is set if new data

;received

; Check for <Enter> key (0x0d) and execute display function

;============================

;This routine receives control when the <Enter> key is

;received.

;Action:

;1. Clear LCD

;2. Output is set to top LCD line

;3. Characters stored in EEPROM are displayed

;until 0x0d code is detected

isEnter:

call clearLCD

; Clear character counter and line counter variables clrf LCDcount

clrf LCDline

;Read data from EEPROM memory, starting at address 0

;and display on LCD until 0x0d terminator

;At this point character read is not 0x0d

;Display on LCD

; End of execution atEnd:

goto atEnd

;============================================================

;============================================================ ; L O C A L P R O C E D U R E S ;============================================================ ;============================================================ ;==========================

;init LCD for 4-bit mode ;========================== initLCD:

;Initialization for Densitron LCD module as follows:

;4-bit interface

;2 display lines of 16 characters each

;cursor on

;left-to-right increment

;cursor shift right

;no display shift ;=======================|

;=======================

;Procedure to delay

;42 microseconds

;=======================

;Procedure to delay

;5 milliseconds ;======================= delay_5:

;========================

;send 2 nibbles in

;4-bit mode ;========================

;Procedure to send two 4-bit values to Port-B lines

;7, 6, 5, and 4. High-order nibble is sent first

;ON ENTRY:

;w register holds 8-bit value to send

send8:

;==========================

;merge bits ;==========================

;Routine to merge the 4 high-order bits of the

;value to send with the contents of Port-B

;so as to preserve the 4 low-bits in Port-B

;Logic:

;AND value with 1111 0000 mask

;AND Port-B with 0000 1111 mask

;Now low nibble in value and high nibble in

;Port-B are all 0 bits:

;value = vvvv 0000

;Port-B = 0000 bbbb

;OR value and Port-B resulting in:

;ON ENTRY:

;w contain value bits

;ON EXIT:

;w contains merged bits

merge4:

;==========================

;Set address register

;to LCD line 2 ;==========================

;ON ENTRY:

;Address of LCD line 2 in constant LCD_2

line2:

;==========================

;Set address register

;to LCD line 1 ;==========================

;ON ENTRY:

;Address of LCD line 1 in constant LCD_1

line1:

;==========================

;scroll to LCD line 2 ;==========================

;Procedure to count the number of characters displayed on

;each LCD line. If the number reaches the value in the

;constant LCDlimit, then display is scrolled to the second

;LCD line. If at the end of the second line, then LCD is

;reset to the first line.

LCDscroll:

; Test for line limit

movf LCDcount,w

;At this point the end of the LCD line was reached

;Test if this is also the end of the second line movf LCDline,w

;=============================

;LCD display procedure ;=============================

;Sends 20 characters from PIC buffer with address stored

;in variable bufAdd to LCD line previously selected display20:

;===============================

;first text string procedure ;=============================== storeMS1:

;Procedure to store in PIC RAM buffer the message

;contained in the code area labeled msg1

;ON ENTRY:

;variable bufAdd holds address of text buffer

;in PIC RAM

;w register hold offset into storage area

;msg1 is routine that returns the string characters

;and a zero terminator

;index is local variable that holds offset into

;text table. This variable is also used for

;temporary storage of offset into buffer

;ON EXIT:

;Text message stored in buffer

;

;Store offset into text buffer (passed in the w register)

;in temporary variable

;ASSERT: valid string character in w

;store character in text buffer (by FSR)

endstr1:

return

;Routine for returning message stored in program area

;Message has 10 characters

msg1:

;========================

;blank buffer ;========================

;Procedure to store 20 blank characters in PIC RAM

;buffer starting at address stored in the variable

;bufAdd

;============================================================== ; communications procedures ;==============================================================

;Initialize serial Port-for 2400 baud, 8 bits, no parity,

;1 stop

InitSerial:

;Bits 6 and 7 of Port-C are multiplexed as TX/CK and RX/DT

;for USART operation. These bits must be set to input in the

;TRISC register

;where x is value in the SPBRG register and S is 64 if the high

;baud rate select bit (BRGH) in the TXSTA control register is

;clear, and 16 if the BRGH bit is set. For setting to 2400 baud

;using a 10Mhs oscillator at a slow baud rate the formula

;is:

;At slow speed (BRGH = 0)

; 10,000,000 10,000,000

;---------- = ---------- = 2,403.84 (0.16% error)

;

;==============================

;transmit data ;==============================

;Test for Transmit Register Empty and transmit data in w SerialSend:

;==============================

;receive data ;==============================

;Procedure to test line for data received and return value

;in w. Overrun and framing errors are detected and

;remembered in the variable errorFlags, as follows:

;Bit 5 (RCIF) of the PIR1 Register is clear if the USART

;receive buffer is empty. If so, no data has been received

;At this point data has been received. First eliminate

;possible errors: overrun and framing.

;Bit 1 (OERR) of the RCSTA register detects overrun

;Bit 2 (FERR( of the RCSTA register detects framing error

;At this point no error was detected

;Received data is in the USART RCREG register

;error because FERR framing error bit is set

;can do special error handling here - this code simply clears ; and continues

520 Chapter 15

return

;============================================================

; local EEPROM data procedures

;============================================================

;GPRs used in EEPROM-related code are placed in the common

;RAM area (from 0x70 to 0x7f). This makes the registers

;accessible from any bank.

;==============================

;read local EEPROM ;==============================

;Procedure to read EEPROM memory

;ON ENTRY:

;Address of EEPROM memory location to read is stored in

;local register EEMemAdd

;ON EXIT:

;Read data in w

EERead:

;==============================

;write local EEPROM ;==============================

;Procedure to write data byte to EEPROM memory

;ON ENTRY:

;Address to write stored in local register EEMemAdd

;Data byte to write is in local register EEByte EEWrite:

Bank3

Wait2Start:

;Re-enable interrupts if program uses interrupts

;If not, comment out next line

;============================================================

end ; END OF PROGRAM

;============================================================

15.2.3 I2CEEP Program

;File name: I2CEEP.asm

;Last revision: May 28, 2006

;Author: Julio Sanchez

;Processor: 16F877

;Description:

;Receive character data through RS-232 line and store in

;24LC04B EEPROM IC, using the I2C serial protocol in the

;PIC’s MSSP module. Received characters are echoed on

;the second LCD line. When <Enter> key is detected (code