LCD ubable to get to work

[Geoff Wrightson]

**Hi I am trying to interface a 16x2 alphanumeric lcd to a 16f877a but am having no success ,the hardware works with a different hex file loaded into pic and I can write to the port I have lcd connected to to light up LED 's, I am using a modified version of one of GCB example files.
Pic chip is using 20mhz Xtal osc.
Also using command line under ubuntu
linux.
This is the version and date of GCB I have installed Version: 0.98.01 2017-10-27
follows is part of source code.

 #chip 16F877a, 20
 #config BODEN = OFF, PWRTE = ON, WDT = OFF


  ;Setup LCD Parameters
  #define LCD_IO 8
  ;#define LCD_NO_RW
  #define LCD_SPEED SLOW

; ----- Define Hardware settings
  #define LCD_RS PORTA.5
  #define lcd_RW PORTA.4
  #define LCD_Enable PORTA.3
  #define LCD_DATA_PORT PORTD

; ----- Main body of program commences here.
    Do Forever
        CLS
        WAIT 3 s
        PRINT "START TEST"
        locate 1,0
        PRINT "DISPLAY ON"
        wait 3 s

ETC
Any help appreciated.
Geoff

[Anobium]

This code works here.

#chip 16F877a, 20
 #config BODEN = OFF, PWRTE = ON, WDT = OFF

  ;Setup LCD Parameters
  #define LCD_IO 8
  ;#define LCD_NO_RW
  #define LCD_SPEED SLOW

; ----- Define Hardware settings
  #define LCD_RS PORTA.5
  #define lcd_RW PORTA.4
  #define LCD_Enable PORTA.3
  #define LCD_DATA_PORT PORTD

; ----- Main body of program commences here.
    Do Forever
        CLS
        WAIT 3 s
        PRINT "START TEST"
        locate 1,0
        PRINT "DISPLAY ON"
        wait 3 s
loop

Remove LCD_RW and try LCD_NO_RW

[Anobium]

post the completed project including the hex, and, the other hex... what source was that? attach this hex.

just tried on a simulator. also works.

[Geoff Wrightson]

Hi attached are the hex and asm files I'm having difficulty with and also hex that works with hardware setup, I no longer have source code for it . It was something I was playing with a few years ago possibly written in JAL. but not sure .

[Anobium]

I am not certain the old hex is for that chip. Are you 100% certain?

Also, do you know if the LCD is a 4 bit or 8 bit LCD?

Can you take a photo of the back?

Does the chip run? If you connect just an LED via a suitable resistor - and you turn the LED of and off with a small delay. Does the LED flash?

A photo of your setup/rig/board would also help.

I can deasm the HEX and this may shed some light on the old HEX.

I am asking questions like these as we must have 1000's of solutions with LCDs and I do not expect any issues with the library or core LCD functions.

[Geoff Wrightson]

Hi thanks very much for your help with this much appreciated, yes old hex is definately for this chip and have test with a leds connected to port and all works......... I am using a prototype board that is hard wired to the display port 99% sure lcd is 8 bit, but they are
several years old model " PVC160202PGN" maybe I should get a new one to try,

[Anobium]

Not really sure of the issue here.

Can download the attached file. Replace the existing library in the ..\GCB@Syn\GreatCowBasic\Include\lowlevel directory. I have changed the init timings to (maybe) better support older LCDs.

Just to confirm. I have validated this program on real hardware. Only difference is the ports - my board is hard coded. :-)

#chip 16F877a, 20
#config BODEN = OFF, PWRTE = ON, WDT = OFF

;Setup LCD Parameters
#define LCD_IO 8

#define LCD_SPEED SLOW

; ----- Define Hardware settings
#define LCD_RW PORTE.1
#define LCD_RS PORTE.0
#define LCD_Enable PORTE.2
#define LCD_DATA_PORT PORTD

; ----- Main body of program commences here.
  Do Forever
      CLS
      WAIT 3 s
      PRINT "START TEST"
      locate 1,0
      PRINT "DISPLAY ON"
      wait 3 S
loop

[Geoff Wrightson]

Hi still no good ........ each bit on portD has a led attached when I run oldhex file they blink away but when I load lcd8-877a.hex there is no activity the chip oscillator is running and the top line of the LCD is 16 full blocks, also did a search for lcd.h and appart form the GCB there is several other files called lcd.h..... no sure if this has any relavance. I will go to the local electronics store in the morning and buy a new lcd and see if that makes any difference tho the one I have works with oldhex file.
Geoff.

[Anobium]

Can you try the 4-bit LCD? But, are you 100% certain about this port assignments? Try the code below but check the port assignments.

Not sure where you are finding those other LCD.H files - a screen shot would help.

  ;Setup LCD Parameters
  #define LCD_IO 4
  #define LCD_NO_RW

  #define LCD_Speed slow

  ;Change as necessary
  #define LCD_RS Porta.5
  #define LCD_Enable Porta.3
  #define LCD_DB4 Portd.0
  #define LCD_DB5 Portd.1
  #define LCD_DB6 Portd.2
  #define LCD_DB7 Portd.3

[Anobium]

And, I cannot load the oldhex into... a simulator, Pk2, pk3 or MPLAB. Errors all the time.

File has no Config in pk2&pk2, MPLAB states the checksum is incorrect and the file in the emulator is meaningless. So.... how are you programming?

I have removed the UNIX file format to get the file even to load.

[Geoff Wrightson]

Hi just tried hex file again "oldf877a.hex" and it works ok , programmed pic using linux program "picprog" I have attached hex again .

[Geoff Wrightson]

Hi attached is screenshot of lcd.h file locations .

[Anobium]

Thank you.

File photo. We only have one lcd.h relative to Great Cow BASIC. So, no worries there.
File is not correct. Will not load. There format is one I have never seen before with respect to having two lines of data on one one line.
Try 4-bit. Please.

[Geoff Wrightson]

Have tried the 4 bit mode still no go have programmed a 16f887 and bread boarded circuit but still no go I can write to portd and count with led's attached but no go with lcd program there is no activity on data pins monitored with led's . this is the command line I am using " gcbasic /A:GCASM lcd8-887.gcb"

[Anobium]

command line looks ok. Send me this whole project in a zip. Let us compare what is being generated.

I have never seen anything like this - every. Most odd.

[Anobium]

just noticed... are you using a 877a or an 877? Last post stated 877.

[Geoff Wrightson]

I have was originally using a 16f877a on a hardwired prototyping board but last try was using a 16f887 using breadboard but still with same result. I wonder if it is to do with using linux?.
Attached is zip file.

[Anobium]

Nothing obvious.

change to... guessing your oscillator.

 #config BODEN = OFF, PWRTE = ON, WDT = OFF, osc=EXTRC

[Anobium]

Hugh and I have looked at this. The original HEX is not valid 'The working hex is weird, all the addresses and line sizes are wrong'. I cannot get this operate on a chip, in a PICKit or MPLAB.

Can you please a detailed photo of the back on the LCD?

Try this

 #config BODEN = OFF, PWRTE = ON, WDT = OFF, osc=EXTRC

Evan

[Geoff Wrightson]

Hi have attached a few photos and will try config line.
Geoff

[Geoff Wrightson]

config line made no difference
checked pulses with cro rs = 6ms low pulse, e = 2ms high pulse; data pulses 2ms.
geoff

[Anobium]

I can confirm this code works. I have built a standalone test rig on a breadboard. i have tested with a number of LCDs all work.

#chip 16F877a, 20

;Setup LCD Parameters
#define LCD_IO 8

#define LCD_SPEED SLOW

; ----- Define Hardware settings
#define LCD_RW PORTE.1
#define LCD_RS PORTE.0
#define LCD_Enable PORTE.2
#define LCD_DATA_PORT PORTD

; ----- Main body of program commences here.

  Do Forever
      CLS
      WAIT 1 s
      PRINT "28.04.18:12:11"
      locate 1,0
      PRINT "Anobium"
      wait 5 S
loop

My guess. Is your board missing a 10k pull-up on MCLR.

[Anobium]

I recognise(ish) your board. It is based in the PIC40 board. Should work.

I cannot datasheet on LCD. Must be old. This could be a timing issue or protocol issue - flying blind without a datasheet.

[Geoff Wrightson]

Hi attached code works tho only displays 1 character .
Geoff.

[Anobium]

What is different from previous attempts? I would be guessing.