GCBASIC / Discussion / Help: i2c Serial Adapter to 4x20 LCD Display problem.

Could someone please point out the errors of my ways. After fumbling around on the Dark Side with my Spindle Cooling Controller project and Arduino for a couple of weeks, I gave up and decided at great cost to invest in a PCF8574N i2c to 8 bit decoder and use one of my little 16F18326 SBC (Single Board Computer) which has most of the features I need for the project.

So here I am at the first Hurdle, Failed..... or more to the point fallen.

I am trying to get my i2c bus to talk with a 4x20 LCD Display, I have dug out of the the Demo's some code written by Evan but I cannot get it to work. in the attachments is an image of my i2c Discovery showing the i2c adapter sits at 0x7E which is peculiar as in Arduino speak the same adapter sits on 0x3F.

the other noticeable thing is there is no back-light command ??

As always any help or comments is greatly appreciated.

The code I have is as follows:

'''A demonstration program for GCGB and GCB.
'''----------------------------------------------------------------------------------
'''----------------------------------------------------------------------------------
'''This program demonstrates shows one LCD (16x2 & 16x4) being driven using a LCD I2C
'''adapters.
'''This uses the GCB hardware implementation of IC2 for Microchip devices.
'''Two types are supported as shown below.  This example is using "#define LCD_IO 10"
'''- Set LCD_I0 to 10 for the YwRobot LCD1602 IIC V1 or the Sainsmart LCD_PIC I2C adapter.
'''- Set LCD_I0 to 12 for the Ywmjkdz I2C adapter with pot bent over top of chip.
'''- Use the following to address a diferent I2C device.
'''- #define LCD_I2C_Address 0x4e This is the default value, change as appropiate
'''@author  EvanV
'''@licence GPL
'''@version 1.0a
'''@date    21.10.2015
'''********************************************************************************


    #chip 16f18326,32

    #option explicit




    'Set the PPS for this solution.
  #startup InitPPS, 85



    #include <lowlevel\hwi2c.h>
  ; ----- Define Hardware settings
  ' Define I2C settings
  #define HI2C_BAUD_RATE 100
    #define hi2c_DATA PORTC.1
    #define hi2c_CLOCK PORTC.0
  'I2C pins need to be input for SSP module
  Dir HI2C_DATA in
  Dir HI2C_CLOCK in
  'MASTER MODE
  HI2CMode Master


  '''Set up LCD
   #define LCD_IO 10
   #define LCD_I2C_Address_1 0x7F
  ' #define LCD_I2C_Address_1 0x7E

   'You may need to use SLOW or MEDIUM if your LCD is a slower device.
   #define LCD_SPEED SLOW
   'You may need to invert these states. Dependent of LCD I2C adapter.
   #define LCD_Backlight_On_State  1
   #define LCD_Backlight_Off_State 0

; ----- Constants
  'None required beyond the scope of the hardware.

; ----- Quick Command Reference:

 '''Set LCD_10 to 10 for the YwRobot LCD1602 IIC V1 or the Sainsmart LCD_PIC I2C adapter
 '''Set LCD_10 to 12 for the Ywmjkdz I2C adapter with pot bent over top of chip

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

    wait 100 ms
    CLS
    PRINT "Great Cow Basic"
    Locate 1,0
    Print "@v.0.95.010"
    WAIT 3 s

    Do Forever
        CLS
        WAIT 3 s
        PRINT "START TEST"
        locate 1,0
        PRINT "DISPLAY ON"
        wait 3 s

        CLS
        Locate 0,0
        Print "Cursor ON"
        Locate 1,0
  '      LCDcursor CursorOn
        wait 3 S
        CLS
'        LCDcursor CursorOFF
        locate 0,0
        Print "Cursor OFF"
        wait 3 s
        CLS
        Locate 0,0
        Print "FLASH ON"
        Locate 1,0
'        LCDcursor FLASHON
        wait 3 s

        CLS
        locate 0,0
        Print "FLASH OFF"
'        LCDCURSOR FLASHOFF
        wait 3 sec

        Locate 0,0
        Print "CURSR & FLSH ON"
        locate 1,0
'        LCDCURSOR CURSORON
'        LCDCURSOR FLASHON
        Wait 3 sec

        Locate 0,0
        Print "CURSR & FLSH OFF"
        locate 1,0
'        LCDCURSOR CursorOFF
'        LCDCURSOR FLASHOFF
        Wait 3 sec

        CLS
        Locate 0,4
        PRINT "Flashing"
        Locate 1,4
        Print "Display"
        wait 500 ms

        repeat 10
'            LCDCURSOR LCDOFF
            wait 500 ms
'            LCDCURSOR LCDON
            wait 500 ms
        end repeat
        CLS
        Locate 0,0
        Print "DISPLAY & BACKL."
        Locate 1,0
        Print "FOR 5 SEC"
        Wait 2 SEC
'        LCDCURSOR LCDOFF
  '      LCDBacklight OFF
        WAIT 5 s
   '     LCDBacklight ON
        CLS
        Locate 0,0
'        LCDCURSOR LCDON
        Print "END TEST"
        wait 3 s
    loop

  Sub InitPPS
    UNLOCKPPS

        RC1PPS = 0x19            ' RC1<-MSSP1:SDA1
        SSP1CLKPPS = 0x10        ' RC0->MSSP1:SCL1
        SSP1DATPPS = 0x11        ' RC1->MSSP1:SDA1
        RC0PPS = 0x18            ' RC0->MSSP1:SCL1

      LOCKPPS
  End sub
end

Capture10.JPG

Hi Keith

Try this simplified code.
Do you get a display?
Does the backlight come on?

#chip 16f18326,32
#option explicit
#startup InitPPS, 85

#define HI2C_BAUD_RATE 100
#define hi2c_DATA PORTC.1
#define hi2c_CLOCK PORTC.0

Wait 500 ms  'stabilize

'MASTER MODE
 HI2CMode Master

'''Set up LCD
#define LCD_IO 10
#define LCD_I2C_Address_1 0x7E

#define LCD_SPEED SLOW
#define LCD_Backlight_On_State  1
#define LCD_Backlight_Off_State 0

LCDBacklight ON
wait 100 ms
CLS

Locate 0,0
PRINT "Great Cow Basic"

Do
Loop

Sub InitPPS

   'Module: MSSP1
   SSP1CLKPPS = 0x0010    'RC0 > SCL1
   RC0PPS = 0x0018        'SCL1 > RC0 (bi-directional)

   RC1PPS = 0x0019        'SDA1 > RC1
   SSP1DATPPS = 0x0011    'RC1 > SDA1 (bi-directional)

End Sub

Last edit: William Roth 2023-01-26

William Roth - 2023-01-25

Try changing the address to 0x7E. This is the address I use for these adapters.

Have you adjusted the contrast potentiometer on the PFC 8574 Backpack module? The voltage at the contrast pin on the LCD module ( center tap of pot) should typically be about 1/2 volt.

Last edit: William Roth 2023-01-26

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Anobium - 2023-01-26

The address is 0x7E. The I2C discovery shows the two address the write and read addresses.

Also, see https://github.com/GreatCowBASIC/Demonstration_Sources/tree/main/Vendor_Boards/Great_Cow_Basic_Demo_Board/16f18326_ChipRange_Demonstrations

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Keith - 2023-01-26

@William,
Hi again William and thank you for your help. This is really becoming another nemesis to me, The little OLed GLCG works a treat on these board of mine but for the life of me I cannot get a wink let alone a twinkle out of an 4x20 LCD.

Some of the things I found wrong in the code was the i2c baud rate and the i2c port addresses.

' 16F18326 ' ------- ' VDD-|1 14|-Vss ' RA5-|2 13|-RA0 - DAT ' AN4 IN RA4-|3 12|-RA1 - CLK ' MCLR RA3-|4 11|-RA2 ' RC5-|5 10|-RC0 - I2C CLK ' modeBut RC4-|6 9|-RC1 - I2C DAT ' setBut RC3-|7 8|-RC2 ' ------

on my SBC'c the i2c Clock and Data pins are C0 and C1

I'm still unsure about the PCF8574T IC2/Serial_Expander address. i2c Discovery still reports 0x7E as the address but the same adapter and Display is plugged into the Black Arts Arduino on the Dark Side it it's address is 0x3E

Still nothing on the display and no backlight

When I compile your code I get an error on the line LCDBacklight ON which I have to rem out to get it to compile.

It's really frustrating that I'm falling down flat on my hooter with something as basic as this.
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Keith - 2023-01-26

@William,
Hi again William and thank you for your help. This is really becoming another nemesis to me, The little OLed GLCG works a treat on these board of mine but for the life of me I cannot get a wink let alone a twinkle out of an 4x20 LCD.

Some of the things I found wrong in the code was the i2c baud rate and the i2c port addresses.

' 16F18326 ' ------- ' VDD-|1 14|-Vss ' RA5-|2 13|-RA0 - DAT ' AN4 IN RA4-|3 12|-RA1 - CLK ' MCLR RA3-|4 11|-RA2 ' RC5-|5 10|-RC0 - I2C CLK ' modeBut RC4-|6 9|-RC1 - I2C DAT ' setBut RC3-|7 8|-RC2 ' ------

on my SBC'c the i2c Clock and Data pins are C0 and C1

I'm still unsure about the PCF8574T IC2/Serial_Expander address. i2c Discovery still reports 0x7E as the address but the same adapter and Display is plugged into the Black Arts Arduino on the Dark Side it it's address is 0x3E

Still nothing on the display and no backlight

When I compile your code I get an error on the line LCDBacklight ON which I have to rem out to get it to compile.

It's really frustrating that I'm falling down flat on my hooter with something as basic as this.
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Anobium - 2023-01-27

The Arduino address is correct for that language. I will explain.

Arduino uses a 7bit address plus a read or write bit. So, to communicate with a Slave I2C device the Arduino compiler does this. 0x3E shifted to the left plus the Read bit (0) or Write Bit (1).

So, this means 0x3E * 2 = 0x7C; add 0 or 1 give an 8 address of 0x7C (read) or 0x7D (write).

However, the addresses shown in the I2C discovery JPG above shows addresses 0x7E/0x7F which means the something is odd.

Please rerun the I2C discovery from the URL I posted, adapted only for I2C ports. I want to see the complete terminal screen.

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William Roth - 2023-01-27

I see nothing odd ...

The chip is likely a PC7584"A" Version. If it works with Arduino at address 0x3E, then it should work with GCB at Address 0x7E.

These are the only possible addresses for this chip:

0X70
0x72
0x74
0x76
0x78
0x7A
0X7C
0X7E

The address is determined by the states of Pins 1,2,&3. I have not seen these at any other address than 0x7E for 8-bit addressing. If Pins 1,2 & 3 are all 5V then the 12c address for GCB is 0x7E.

My guess is there is something wrong other than the I2C Address. We know it's communicating, because the discovery returns 0x7E for the address.

Note: This chip/LCD combo will absolutely not operate at 3.3V so make sure the supply voltage is at least 4.5 V with 5V being preferred.

Also there will be no visible display if the contrast pot on the backpack board is not adjuster correctly. Also check that the clock and data signals are not reversed.

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I have done as you said Evan and compiled the i2c Discovery the Git hub repository with some changes which right or wrong I thought were needed..

' ----- Configuration
'Chip Settings.
#CHIP 16f18326,32
#OPTION Explicit


#INCLUDE <lowlevel\hwi2c2.h>


'Set the PPS of the PWM and the RS232 ports.
'Set the PPS for this solution.
#STARTUP InitPPS, 85



#DEFINE SWITCH_DOWN         1
#DEFINE SWITCH_UP           0

**'' I had to add these two lines **

        #define LCD_IO 10
        #define LCD_I2C_Address_1 0x7E
''
'' -------------------LATC-----------------
'' Bit#:  -7---6---5---4---3---2---1---0---
'' LED:   ---------------|D5 |D4 |D3 |D2 |-
''-----------------------------------------
''
**Had to reconfigure the ports as C.0 and C.1 are used for my i2c bus **

#DEFINE LEDD2  PORTC.2
#DEFINE LEDD3  PORTC.3
#DEFINE LEDD4  PORTC.4
#DEFINE LEDD5  PORTC.5
#DEFINE LEDBANK portc
#DEFINE SWITCH      PORTA.1



Dir     LEDD2 Out
Dir     LEDD3 Out
Dir     LEDD4 Out
Dir     LEDD5 Out
Dir     SWITCH In

#DEFINE USART_BAUD_RATE 19200
#DEFINE USART_TX_BLOCKING


' ----- Define Hardware settings for HWI2C2
' Define I2C settings - CHANGE PORTS if required for your specific device.
#DEFINE HI2C2_BAUD_RATE 400
#DEFINE HI2C2_DATA PORTC.1
#DEFINE HI2C2_CLOCK PORTC.0
'Initialise I2C Master
'I2C pins need to be input for SSP2 module
Dir HI2C2_DATA In
Dir HI2C2_CLOCK In
'MASTER Second Port
HI2C2Mode Master



' ----- Main body of program commences here.
' Now assumes Serial Terminal is operational
Dim DeviceID As Byte
Dim DISPLAYNEWLINE As Byte

HSerPrintCRLF
HSerPrint "Hardware I2C2 "
HSerPrintCRLF 2

Do Forever
    Set LEDD2 Off
    Set LEDD3 Off
    Set LEDD4 Off
    Set LEDD5 Off

    HSerPrint "     "
    For DeviceID = 0 To 15
        HSerPrint Hex(deviceID)
        HSerPrint " "
    Next

    For DeviceID = 0 To 255
        DisplayNewLine = DeviceID % 16
        If DisplayNewLine = 0 Then
            HSerPrintCRLF
            HSerPrint Hex(DeviceID)
            HSerPrint ": "
        End If
        HSerPrint " "
        HI2C2Start
        If HI2C2WaitMSSPTimeout <> TRUE Then

            HI2C2Send ( deviceID )

            If HI2C2AckpollState = FALSE Then
                HSerPrint   Hex(deviceID)
            Else
                HSerPrint "--"
            End If
            HI2C2Send ( 0)


        End If
        HI2C2Stop

    Next

    HSerPrintCRLF 2
    HSerPrint   "End of Search - Press button to repeat test"
    HSerPrintCRLF 2
    Set LEDD2 On
    Set LEDD3 On
    Set LEDD4 On
    Set LEDD5 On

    Wait While switch = SWITCH_UP
Loop

Sub InitPPS
    UNLOCKPPS
    'Pin RC5 source is an input for RX
    RXPPS  = 0x15
    'Pin RC4 source is TX/CK
    RC4PPS = 0x14

    'RA2->MSSP2:SDA2;
    RA2PPS = 0x001b
    'RA2->MSSP2:SDA2;
    SSP2DATPPS = 0x0002
    'RA4->MSSP2:SCL2;
    SSP2CLKPPS = 0x0004
    'RA4->MSSP2:SCL2;
    RA4PPS = 0x001a
    LOCKPPS
End Sub

End

These is the results from my terminal

Hardware I2C2

 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

00:
10:
20:
30:
40:
50:
60:
70:
80:
90:
A0:
B0:
C0:
D0:
E0:
F0:

End of Search - Press button to repeat test

 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

00:
10:
20:
30:
40:
50:
60:
70:
80:
90:
A0: A9

Anobium - 2023-01-27

I will try this code for you. This needs to verified.

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@Kieth. I took you code, removed the two comments and compiled and got the display below.

For your results where you get NO -- then you may have the DATA line disconnected.

Inspect your circuit. With the power off. Do you have the 2k-5k(ish) on the DATA line pullup to 5v0, and do you have the 2k-5k(ish) on the LOCK line pullup to 5v0 ? These pullsup must be there ( there may be many that say you can use the internal pullsup but you cannot verify the circuit and it prevents reusable code as the internal pulls are specific to a chip).

Hardware I2C2 

 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 
00:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
10:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- 4E 4F
50:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
80:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
90:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
A0:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
B0:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
C0:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
D0:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
E0:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
F0:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

End of Search - Press button to repeat test

Once I confirmed the I2c address using your program. I loaded C:\GCstudioDemo\GreatCowBASIC\demos\Vendor_Boards\Great_Cow_Basic_Demo_Board\16f18326_ChipRange_Demonstrations\24_using_ic2_lcd_1602_display.gcb with no changes and it worked.

My chip on the LCD is a 8574T.

Last edit: Anobium 2023-01-28

20230128_074047.jpg

Anobium - 2023-01-28

@Kieth. I did notice.

Your I2C discover is using the second I2C channel and the LCD demo I used was the first I2C channel.

This is all good. I am just pointing it out. Using second I2C channel for i2C discovery needs to work regardless.

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Anobium - 2023-01-28

@Kieth. My hex, from your code, this will rule out your compiler and toolchain. It works here.

KiethI2C.hex

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Keith - 2023-01-28

This is really, really getting to me now. I have replaced the PCF8574T Serial adapter, Display and even put another 16F18326 onto a breadboard wired it up including the 4k7 Pull-ups on the i2c Clock and data lines and still with your Keithi2c.hex file, Now't, Nada Nix, in other words Nothing.

To add insult to my battered confidence, I hooked the little SSD1306 GLCD display up and loaded my Clock and Temperature code onto both the breadboard 16F18326 and my little 16F18326 SBC and it sprang into life on both occasions.

To make matters worse, I crossed onto the dark side and booted an Arduino Uno with the 4x20 LCD and 2x20 LCD and within a couple of minutes both were nattering away happily with both displays.

This has gone on for nearly three days now trying to get this project of the ground, my patience is running a bit thin. I don't want to go down the Arduino route, I keep getting stuck with those curly braces among other things.

As a final resort, could you let me see the code you created for the Keithi2c.hex to see if I can cross reference it with what I have.

After that it is time for some serious Recreational Chemistry.

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- Anobium - 2023-01-29
  
  I hope the Chemistry helped.
  
  What results did you get with Keithi2c.hex ? No serial ? Nothing or something ?
  
  The code I used fro Keithi2c.hex was the code you post yesterday. I removed the two comments and compiled. See attached.
  
  The Arduino is an option.
  
  Do have any test equipment ? like an scope or protocol analyser.?
  
  Last edit: Anobium 2023-01-29
  
  KiethI2C.asm
  
  KiethI2C.gcb
  
  KiethI2C.hex
  
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i2c Serial Adapter to 4x20 LCD Display problem.

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i2c Serial Adapter to 4x20 LCD Display problem.