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Greetings PICperts!
Can anyone share a code that will write to the internal memory of PIC16F876A the value "1234"
and display the value when I press a button. I have download an example but I don't really understand how it works.. A simple code will be great to help me get started.
joe
Compiled OK with line...
pbpw -p16f876a sample -v
Lots of embedded comments to tell you what's happening...
Enjoy
Code:' Sample.BAS
' ==========
' Target Processor PIC16F876A-04
'
' Write value '1234' to internal EEPROM
' When Button Pressed Read EEPROM value and Display on LCD
'
'
' CPU Hardware Layout
' -------------------
'
' PortA.0 - Unused - Set to INPUT
' PortA.1 - Unused - Set to INPUT
' PortA.2 - Unused - Set to INPUT
' PortA.3 - Unused - Set to INPUT
' PortA.4 - Unused - Set to INPUT
' PortA.5 - Unused - Set to INPUT
'
' PortB.0 - Button - Connect between this PIC Pin and Vss (0v)
' - uses internal PICs pull-up's
' PortB.1 - Unused - Set to OUTPUT
' PortB.2 - LCD - RS
' PortB.3 - LCD - E
' PortB.4 - LCD - DB4
' PortB.5 - LCD - DB5
' PortB.6 - LCD - DB6
' PortB.7 - LCD - DB7
'
' PortC.0 - Unused - Set to OUTPUT
' PortC.1 - Unused - Set to OUTPUT
' PortC.2 - Unused - Set to OUTPUT
' PortC.3 - Unused - Set to OUTPUT
' PortC.4 - Unused - Set to OUTPUT
' PortC.5 - Unused - Set to OUTPUT
' PortC.6 - Unused - Set to OUTPUT
' PortC.7 - Unused - Set to OUTPUT
'
' PIC Defines
' -----------
@ DEVICE pic16F876A, XT_OSC ' System Clock Options
@ DEVICE pic16F876A, WDT_ON ' Watchdog Timer
@ DEVICE pic16F876A, PWRT_ON ' Power-On Timer
@ DEVICE pic16F876A, BOD_ON ' Brown-Out Detect
@ DEVICE pic16F876A, LVP_OFF ' Low-Voltage Programming
@ DEVICE pic16F876A, CPD_OFF ' Data Memory Code Protect
@ DEVICE pic16F876A, PROTECT_OFF ' Program Code Protection
@ DEVICE pic16F876A, WRT_OFF ' Flash Memory Word Enable
'
' Hardware Defines
' ----------------
'
' LCD Display
' -----------
Define LCD_DREG PORTB ' Port for LCD Data
Define LCD_DBIT 4 ' Use upper 4 bits of Port
Define LCD_RSREG PORTB ' Port for RegisterSelect (RS) bit
Define LCD_RSBIT 2 ' Port Pin for RS bit
Define LCD_EREG PORTB ' Port for Enable (E) bit
Define LCD_EBIT 3 ' Port Pin for E bit
Define LCB_BITS 4 ' Using 4-bit bus
Define LCD_LINES 2 ' Using 2 line Display
Define LCD_COMMANDUS 2000 ' Command Delay (uS)
Define LCD_DATAUS 50 ' Data Delay (uS)
'
' Button Inputs
' -------------
ButtonPRESS var PortB.0 ' Push Button
'
' EEPROM
' ------
MemoryA DATA @0,0 ' The TWO memory locations for saving WORD variable
MemoryB DATA 0 ' Both Preset to Zero
'
' RAM Assignments & Variables
' ---------------------------
WORDVariable var WORD ' Just a WORD variable we're going to use
'
' Start Program
' =============
'
' Set-up Hardware
' ---------------
TRISA=%00111111 ' All available PortA is Input
' Remember it's still in ANALOG Mode
TRISB=%00000001 ' All PortB is Output - except
' B.0 = Button
TRISC=%00000000 ' All PortC is Output
CMCON=%00000111 ' Disable Comparators
CVRCON=%00000000 ' Disable Reference Module
OPTION_REG.7=0 ' Enable Weak Pull-Up's
Pause 2000 ' Wait for LCD to settle
'
' Save Value into EEPROM
' -----------------------
WORDVariable=1234
LCDOut $FE,1,"Writing=",#WordVariable ' Tell user what we're doing...
WRITE MemoryA,WORDVariable.HighByte ' Save one Byte from Word to EEPROM Location 0
WRITE MemoryB,WORDVariable.LowByte ' Save other Byte from Word to EEPROM Location 1
Pause 2000 ' Just a pause so you can read what's on the LCD
'
' Prompt for Button Press
' -----------------------
PromptLoop:
LCDOut $FE,1,"Press Button..."
While ButtonPRESS=1:Wend ' Wait here until Button Pressed
READ MemoryA,WORDVariable.HighByte ' Reconstruct Word variable from EEPROM
READ MemoryB,WORDVariable.LowByte
LCDOut $FE,1,"Reading=",#WORDVariable ' Display Result
While ButtonPress=0:Wend ' Wait here as long as finger is on Button
Goto PromptLoop
'
End
Melanie,
Thanks for your fast reply, I will work this out and let you know the outcome later.
regards,
joe
Thank you for the great sample, Melanie.
The comments make it a real tutorial on reading and writing to EEPROM. The logic and flow are a glimpse into the world of how professionals write code. Very impressive.
I will be studying this masterpiece for some time to come.
-Adam-
Hi Melanie!
Is the sample.bas that you posted about how to read and write the EEPROM applicable for 16F877A?
If not, what certain modifications should be done?
Please help...
ria
Adam - *blush* personally Signed framed Masterpieces are available in exchange for internationally negotiable crinkly drinking vouchers...
Ria - Yes it is, with a few changes...
1. Change ALL the PIC defines to 877A instead 876A...
eg
@ DEVICE pic16F876A, XT_OSC
becomes
@ DEVICE pic16F877A, XT_OSC
2. Add additional TRIS statements to account for Ports D and E.
eg
TRISE=%11111111
Remembering that parts of PortE will still have Analog on them...
3. Compile with the command line
PBPW -p16f877A sample -v
I see..
Thank you so much Melanie..
I really learn a lot from this forum.
Cheers!
ria
By the way Melanie..why we need to use PBPW instead of PBP in compiling?
What's the difference between them?
Hi Melanie,
I got your code running, initially I placed '9999' at memory location 0. I'm trying
to read it from the internal memory, So I try this code below. But when I press the button I got '655535'
instead the initial value '9999'.
TRISB=%00010000 ' All PortB is Output - except
' B.3 = Button
TRISC=%00000000 ' All PortC is Output
CMCON=%00000111 ' Disable Comparators
CVRCON=%00000000 ' Disable Reference Module
OPTION_REG.7=0 ' Enable Weak Pull-Up's
Pause 2000
ButtonPRESS var PortB.4 ' Push Button
WORDVariable var WORD
PromptLoop:
Serout PortC.1,6, [$FE,1,"Press Button..."]
While ButtonPRESS=1:Wend ' Wait here until Button Pressed
READ 0,WORDVariable.HighByte ' Reconstruct Word variable from EEPROM
READ 1,WORDVariable.LowByte
Serout PortC.1,6, [$FE,1,"Reading=",#WORDVariable] ' Display Result
While ButtonPress=0:Wend ' Wait here as long as finger is on Button
Goto PromptLoop
'
End
Thanks for the time, appreciate it very much,
joe
Make sure your PIC programmer program the EEPROM location, unless.. you may read an empty EEPROM $FFFF
Now depending of how you wrote your DATA line, this may work.. or not.
should work.Code:data @0, WORD 9999
Your PICProgrammer software should allow to see the EEPROM section, just compile your code, import the .HEX and look if your data is saved in the EEPROM.
Thanks all, I got it to work. But I've noticed that every time I compile it the data '9999' in Address 0 restarts to 655535. How can I prevent it from overwriting. So that every time I check Address 0 the same data will show.
Thanks all,
joe