I2CRead & I2CWrite not working as expected


+ Reply to Thread
Results 1 to 31 of 31
  1. #1
    Join Date
    Jul 2003
    Posts
    2,358

    Default I2CRead & I2CWrite not working as expected

    I can't seem to Write properly to an I2C device
    I can't seem to Read properly back from an I2C device
    My I2C Serial EEPROM doesn't always save my data
    I can't Write to the Registers on my I2C Real Time Clock, ADC etc



    Check your I2CRead and IC2Write statements...

    Do you have any CONSTANTS in the device address?

    If so, your code is flawed... remove the constants and put in VARIABLES in their place...


    Example: Write to location 8 on a 24LC32... these are NOT CORRECT...

    I2CWrite SDA,SCL,$A0,$08,[DataA]
    I2CWrite SDA,SCL,$A0,8,[DataA]
    I2CWrite SDA,SCL,$A0,$0008,[DataA]
    I2CWrite SDA,SCL,$A0,%00001000,[DataA]
    I2CWrite SDA,SCL,$A0,%0000000000001000,[DataA]


    Example: Write to location 8 on a 24LC32... this is CORRECT...

    I2CAddress=8
    I2CWrite SDA,SCL,I2CDevice,I2CAddress,[DataA]

    where previously I2CAddress has been defined as a WORD, and I2CDevice has been defined as a BYTE and preloaded with $A0.

    Remember that the type of VARIABLE I2CAddress must match the requirement for the device you are addressing... eg it's a WORD for devices like a 24LC32 or 24LC64, but it's a BYTE for other devices like a 24LC16 or DS1307 RTC. Check your device Datasheet.

  2. #2
    Join Date
    Jan 2005
    Location
    France
    Posts
    95

    Default Use of the last label at the end of a I2CWRITE

    Always and again Thanks Melanie for the support.
    Just one question about the "label" at the end of a I2CWRITE command
    I see in the help menu this sentence "If the optional Label is included, this label will be jumped to if an acknowledge is not received from the I2C device. "
    My question :
    Could we say this is a GOTO or a GOSUB command ?

    I was "swimming" when I was building a prototype WITHOUT the I2C module
    (TV RECEIVER MODULE) connected ....
    Program was working ... let say 6 times ... and seems to go in a strange loop
    ... I would say a "dead loop" .... I use a Blinking led to follow the process !

    I have removed this label, now it is working

    Label is a sub routine with a return ...
    I am sure I am wrong somewhere !
    thanks in advance
    Francois

  3. #3
    skimask's Avatar
    skimask Guest

    Default

    Quote Originally Posted by F1CHF View Post
    My question :
    Could we say this is a GOTO or a GOSUB command ?
    It would be a GOTO command. I suppose it's a question of how you read the manual.
    If the manual said 'If the optional Label is included, this label will be ----CALLED---- if an acknowledge is not received from the I2C device', then I would reasonably assume that it would be a goto...
    But, the manual says 'this label will be ----JUMPED TO---- if an acknowledge....'. That tells me it's a GOTO.

    If all else fails, check your .lst file and see what the compiler puts in there for you. Make a few 'special' labels so you can follow yourself thru the .lst file and search them in the file. You should be able to find what you need.

  4. #4
    Join Date
    Jan 2005
    Location
    France
    Posts
    95

    Thumbs up I2Cwrite error label

    OK good, let assume this is a GOTO, that will explain my application
    was going on a dead loop with a return ..
    I must try to find a PBP Help File in FRENCH or read carrefully !
    thanks for this help
    Francois

    Quote Originally Posted by skimask View Post
    It would be a GOTO command. I suppose it's a question of how you read the manual.
    If the manual said 'If the optional Label is included, this label will be ----CALLED---- if an acknowledge is not received from the I2C device', then I would reasonably assume that it would be a goto...
    But, the manual says 'this label will be ----JUMPED TO---- if an acknowledge....'. That tells me it's a GOTO.

    If all else fails, check your .lst file and see what the compiler puts in there for you. Make a few 'special' labels so you can follow yourself thru the .lst file and search them in the file. You should be able to find what you need.

  5. #5
    Join Date
    Sep 2004
    Location
    montreal, canada
    Posts
    6,898

    Default

    good luck to find it in french... unless you want to try GooGLE or else on-line translator that will'nt be better
    Steve

    It's not a bug, it's a random feature.
    There's no problem, only learning opportunities.

  6. #6
    Join Date
    Feb 2013
    Posts
    753

    Default Re: I2CRead & I2CWrite not working as expected

    Code:
    SDA var PORTA.1
    SCL var PORTA.2 
    T1 var byte
    T1=15
    I2CAddress var word 'I2C address
    I2CDevice var byte 'I2C device add
    i2CDevice=$A0
    I2CAddress=8
    I2CWrite SDA,SCL,I2CDevice,I2CAddress,127
    pause 100
    i2cread SDA,SCL,I2CDevice,I2CAddress,T1
    LCDOUT $FE,$c0, "value ", dEC T1
    pause 1000 
    stop
    Ports are set to digital, analog and comparators turned off. 4.7K resistors in place, 24C32 chip is brand new and authentic.
    Only VDD/VSS and SDA/SCL pins are used, others are left floating, according to datasheet.
    The interesting thing is, that i2cread returns nothing - I mean, I added T1=15 just for test, so that 15 is displayed, instead of 127
    whole i2croutine doing nothing?

  7. #7
    Join Date
    Jan 2005
    Location
    France
    Posts
    95

    Default Re: I2CRead & I2CWrite not working as expected

    hello
    start a TEST first to see if your I2C unit is OK
    let go here
    https://playground.arduino.cc/Main/I2cScanner/

    francois

  8. #8
    Join Date
    May 2013
    Location
    australia
    Posts
    1,945

    Default Re: I2CRead & I2CWrite not working as expected

    Only VDD/VSS and SDA/SCL pins are used, others are left floating, according to datasheet.
    start a TEST first to see if your I2C unit is OK
    let go here
    or read the data sheet again and work out the consequences of floating address pins on the device address
    This is more entertaining than Free to Air TV

  9. #9
    Join Date
    Feb 2013
    Posts
    753

    Default Re: I2CRead & I2CWrite not working as expected

    From the datasheet:


    DEVICE/PAGE ADDRESSES (A2, A1, A0): The A2, A1 and A0 pins are device address
    inputs that are hard wired or left not connected for hardware compatibility with
    AT24C16. When the pins are hardwired, as many as eight 32K/64K devices may be
    addressed on a single bus system (device addressing is discussed in detail under the
    Device Addressing section). When the pins are not hardwired, the default A2, A1, and A0
    are zero.
    WRITE PROTECT (WP): The write protect input, when tied to GND, allows normal write
    operations. When WP is tied high to VCC, all write operations to the upper quandrant
    (8/16K bits) of memory are inhibited. If left unconnected, WP is internally pulled down to
    GND.


    The A2, A1, and A0 pins use an internal proprietary circuit that biases them
    to a logic low condition if the pins are allowed to float.

  10. #10
    Join Date
    May 2013
    Location
    australia
    Posts
    1,945

    Default Re: I2CRead & I2CWrite not working as expected

    to my surprise i found the 24c32 on my ds3231 module did not behave as expected when the resistor block [circled] was removed
    to conserve energy for a battery device
    Name:  Screenshot 2021-10-08 164704.jpg
Views: 87
Size:  60.7 KB

    the address was still 0xAE, contrary to the datasheet , so i looked at a data sheet from another manufacturer, where for a 24c32n
    they did not describe this address pin biased low behavior for their version

    to ensure 0xA0 the pins needed to be grounded

    so how sure are you that the datasheet matches the chip?
    its an easy test
    This is more entertaining than Free to Air TV

  11. #11
    Join Date
    Feb 2013
    Posts
    753

    Default Re: I2CRead & I2CWrite not working as expected

    I will try grounding. I will also hook up scope to see what happens.
    I do have pull up resistors in place for SDA/SCL pins.
    Regarding how I know about datasheet?
    I bought this IC from digikey, and downloaded datasheet from the SKU page
    This is genuine atmega part.

  12. #12
    Join Date
    Nov 2003
    Location
    Greece
    Posts
    3,124

    Default Re: I2CRead & I2CWrite not working as expected

    It could be that a static discharge killed the pull down circuitry, so the floating pins may not be a $A0 anymore.

    I had in the past various issues with static and decided to be almost paranoid with this thing. Have anti-static mate on the floor, also on the bench and I earth my self too. Of course the soldering iron is earthed too by a tens of kΩ range resistor.

    Chips from various vendors also have differences and datasheet may not cover that. Richard is right.

    Ioannis

  13. #13
    Join Date
    Feb 2013
    Posts
    753

    Default Re: I2CRead & I2CWrite not working as expected

    Here I connected the scope.
    This is how this code looks:
    My scope (Hantek DSO2D10) Has I2C decode function, but I can't get it running properly.

    Code:
    mainloop:
    
    
       For B0 = 0 To 15 step 2  
         I2CREAD DPIN,CPIN,$A0,B0,X  
         lcdout $fe, $1, dec b0, " ", dec X 
         pause 1000
       Next B0
    
    
    Goto mainloop
    Name:  i2c.jpg
Views: 87
Size:  107.0 KB

  14. #14
    Join Date
    Feb 2013
    Posts
    753

    Default Re: I2CRead & I2CWrite not working as expected

    Oh by the way, I swapped chip with 24C04N - no difference.

  15. #15
    Join Date
    Feb 2013
    Posts
    753

    Default Re: I2CRead & I2CWrite not working as expected

    I set up I2C capture and it looks suspicious.
    The 1st entry at "data" is actually and address of the chip
    and 3rd entry - the address I'm sending to it for reading
    but I'm getting no response?

    Name:  i2ce.jpg
Views: 84
Size:  102.4 KB

  16. #16
    Join Date
    May 2013
    Location
    australia
    Posts
    1,945

    Default Re: I2CRead & I2CWrite not working as expected

    yet still another pointless snippet , with nothing defined


    I2CREAD DPIN,CPIN,$A0,B0,X

    you persist in using incorrect syntax , it should be

    I2CREAD DPIN,CPIN,$A0,B0,[X ]



    proper code, not snippet with undefined rubbish, its not hard
    Code:
    #CONFIG             __config        _CONFIG1,    _FOSC_INTOSC & _CP_OFF & _WDTE_OFF &  _PWRTE_ON  &  _MCLRE_ON  & _CLKOUTEN_OFF
                  __config      _CONFIG2, _PLLEN_ON & _LVP_OFF
    #ENDCONFIG
    ;pic16f1825
    
    DEFINE OSC 32
    OSCCON=$70
    ANSELA=0
    ANSELC=0
    trisa.0=0
    DEFINE I2C_SLOW 1 
    ANSELA = 0
    a Var Byte
    addr Var word
    ar Var Byte
    
    
    SCL var Porta.2                     
    SDA var Porta.1
    lata.0=1
    DEFINE DEBUG_REG PORTA
    DEFINE DEBUG_BIT 0      ;  if not used for pwr  
    DEFINE DEBUG_BAUD 9600
    DEFINE DEBUG_MODE 0     
    pause 2000
    Debug 13,10,"Start",13 ,10
    
    
    a=20
    addr=$200
    I2cwrite Sda,SCL,$a0 ,addr,[a]
    pause 10
    
    
    addr=$200
    I2CREAD Sda,SCL,$a0 ,addr,[ar ]
    debug 13,10,sdec ar
    end
    what a write looks like

    Name:  write.jpg
Views: 83
Size:  73.7 KB

    what a read looks like

    Name:  read.jpg
Views: 86
Size:  90.7 KB
    Last edited by richard; - 9th October 2021 at 10:18.
    This is more entertaining than Free to Air TV

  17. #17
    Join Date
    Feb 2013
    Posts
    753

    Default Re: I2CRead & I2CWrite not working as expected

    Well, if there's syntax error, compiler should warn about it, right?

  18. #18
    Join Date
    Feb 2013
    Posts
    753

    Default Re: I2CRead & I2CWrite not working as expected

    I tried to add brackets and now it starts working, but in the weird way.

    I2CWRITE DPIN,CPIN,$A0,B0,[127]
    Writes 127 into eeprom
    but if I substitute variable there, no matter, byte or word
    after reading, I'm getting zeroes.

  19. #19
    Join Date
    May 2013
    Location
    australia
    Posts
    1,945

    Default Re: I2CRead & I2CWrite not working as expected

    Quote Originally Posted by CuriousOne View Post
    Well, if there's syntax error, compiler should warn about it, right?
    no the compiler produces code to I2CREAD DPIN,CPIN from device $A0 @eeprom address B0,X then read nothing as asked for
    there is no error

    I tried to add brackets and now it starts working, but in the weird way.


    I2CWRITE DPIN,CPIN,$A0,B0,[127]
    Writes 127 into eeprom
    but if I substitute variable there, no matter, byte or word
    after reading, I'm getting zeroes.
    produce a compliable example that demonstrates the problem
    This is more entertaining than Free to Air TV

  20. #20
    Join Date
    Feb 2013
    Posts
    753

    Default Re: I2CRead & I2CWrite not working as expected

    Code:
    DPIN Var PORTA.2       ' I2C data pin
    CPIN Var PORTA.1       ' I2C clock pin
    B0   Var word
    B1   Var byte
    B2   Var byte
    X var byte
    x=0
    
    
       For B0 = 0 To 15    
       b1=b2
         I2CWRITE DPIN,CPIN,$A0,B0,[99]  
         Pause 10        '
    pause 100 
       Next B0
    
    
    mainloop:
    
    
       For B0 = 0 To 15   
         I2CREAD DPIN,CPIN,$A0,B0,[X]  
         lcdout $fe, $1, dec b0, " ", dec X 
         pause 1000
       Next B0
     
       Goto mainloop
     
       End

  21. #21
    Join Date
    May 2013
    Location
    australia
    Posts
    1,945

    Default Re: I2CRead & I2CWrite not working as expected

    Code:
    DPIN Var PORTA.2       ' I2C data pin
    CPIN Var PORTA.1       ' I2C clock pinB0   Var wordB1   Var byteB2   Var byteX var bytex=0   For B0 = 0 To 15       b1=b2     I2CWRITE DPIN,CPIN,$A0,B0,[99]       Pause 10        'pause 100    Next B0mainloop:   For B0 = 0 To 15        I2CREAD DPIN,CPIN,$A0,B0,[X]       lcdout $fe, $1, dec b0, " ", dec X      pause 1000   Next B0    Goto mainloop  
    End
    so we guess whats wrong then

    DPIN,CPIN are analog
    the chip[undefined] has no porta
    the vcc is too low
    the clock is too fast
    the lcd is not setup properly
    the config settings are incorrect
    the interrupt in the unseen part of the code is ruining the timing
    what's the point
    Last edited by richard; - 10th October 2021 at 09:38.
    This is more entertaining than Free to Air TV

  22. #22
    Join Date
    May 2013
    Location
    australia
    Posts
    1,945

    Default Re: I2CRead & I2CWrite not working as expected

    this

    Code:
    '*    pic16f1825      :  eprom addr =$a0   
    #CONFIG
                 __config        _CONFIG1,    _FOSC_INTOSC & _CP_OFF & _WDTE_OFF &  _PWRTE_ON  &  _MCLRE_ON  & _CLKOUTEN_OFF
                  __config      _CONFIG2, _PLLEN_ON & _LVP_OFF
    #ENDCONFIG
    
    
    DEFINE OSC 32
    OSCCON=$70
    ANSELA=0
    ANSELC=0
    trisa.0=0
    DEFINE I2C_SLOW 1 
    ANSELA = 0
    B0   Var word
    X var byte
    SCL var Porta.2                     
    SDA var Porta.1
    lata.0=1
    DEFINE DEBUG_REG PORTA
    DEFINE DEBUG_BIT 0      ;  if not used for pwr  
    DEFINE DEBUG_BAUD 9600
    DEFINE DEBUG_MODE 0     
    pause 2000
    Debug 13,10,"Start",13 ,10
    clear
    For B0 = 0 To 15 
     I2CWRITE sda,scl,$A0,B0,[99]  
     Pause 10        '
    Next B0
    pause 100
    mainloop:
        For B0 = 0 To 15   
         I2CREAD sda,scl,$A0,B0,[X]  
         debug 13,10, dec b0, " ", dec X 
        Next B0 
        pause 1000
    Goto mainloop
    end
    produces as expected this
    Code:
    Start
    
    
    0 99
    1 99
    2 99
    3 99
    4 99
    5 99
    6 99
    7 99
    8 99
    9 99
    10 99
    11 99
    12 99
    13 99
    14 99
    15 99
    This is more entertaining than Free to Air TV

  23. #23
    Join Date
    Feb 2013
    Posts
    753

    Default Re: I2CRead & I2CWrite not working as expected

    Pins are configured properly, LCD also working fine.

    Code:
    TRISA=%00000000  'SET A TO OUTPUT   
    TRISC=%00001101   
    TRISB=%00011000   
    ANSELH=%00000000   ' ADC OFF B
    ANSEL=%000000000 ' turn off ADC
    ADCON1=%10000000  'adc justify
    OSCCON=%01110101  'SET FREQUENCY TO 8MHZ
    WPUB=%00000000    'turn off Pullups
    CM1CON0=0         'DISABLE COMPARATORS
    CM2CON0=0
    This code works, if there is a number [99] or whatever in the write loop
    If I modify that part to look like
    I2CWRITE DPIN,CPIN,$A0,B0,[B1]
    or any other variable instead of B1
    all zeros get written into there, instead of actual variable value.

  24. #24
    Join Date
    May 2013
    Location
    australia
    Posts
    1,945

    Default Re: I2CRead & I2CWrite not working as expected

    This code works, if there is a number [99] or whatever in the write loop
    If I modify that part to look like
    I2CWRITE DPIN,CPIN,$A0,B0,[B1]
    or any other variable instead of B1
    all zeros get written into there, instead of actual variable value.
    what code ?
    minimal, complete and verifiable example MCVE , its not hard

    this code
    Code:
    '*    pic16f1825      :  eprom addr =$a0   #CONFIG
                 __config        _CONFIG1,    _FOSC_INTOSC & _CP_OFF & _WDTE_OFF &  _PWRTE_ON  &  _MCLRE_ON  & _CLKOUTEN_OFF
                  __config      _CONFIG2, _PLLEN_ON & _LVP_OFF
    #ENDCONFIG
    
    
    DEFINE OSC 32
    OSCCON=$70
    ANSELA=0
    ANSELC=0
    trisa.0=0
    DEFINE I2C_SLOW 1 
    ANSELA = 0
    B0   Var word
    b2 var byte
    X var byte
    SCL var Porta.2                     
    SDA var Porta.1
    lata.0=1
    DEFINE DEBUG_REG PORTA
    DEFINE DEBUG_BIT 0      ;  if not used for pwr  
    DEFINE DEBUG_BAUD 9600
    DEFINE DEBUG_MODE 0     
    pause 2000
    Debug 13,10,"Start",13 ,10
    clear
    For B0 = 0 To 15 
      b2=99+b0  
     I2CWRITE sda,scl,$A0,B0,[b2]  
     Pause 10        '
    Next B0
    pause 100
    mainloop:
        For B0 = 0 To 15 
      
         I2CREAD sda,scl,$A0,B0,[X]  
         debug 13,10, dec b0, " ", dec X 
        Next B0 
        pause 1000
    Goto mainloop
    end

    produces as expected




    Code:
    Start
    
    0 99
    1 100
    2 101
    3 102
    4 103
    5 104
    6 105
    7 106
    8 107
    9 108
    10 109
    11 110
    12 111
    13 112
    14 113
    15 114
    This is more entertaining than Free to Air TV

  25. #25
    Join Date
    Feb 2013
    Posts
    753

    Default Re: I2CRead & I2CWrite not working as expected

    The code which I've posted, which writes 99 into eeprom.
    I replace 99 with any other value - it works.
    I put variable name into brackets - it writes zeroes into eeprom.
    no matter what type of variable or what value do it has.

  26. #26
    Join Date
    Feb 2013
    Posts
    753

    Default Re: I2CRead & I2CWrite not working as expected

    Here is full complete code.

    Code:
    ;----[16F886 Hardware Configuration]--------------------------------------------
    #CONFIG
    cfg1 = _INTRC_OSC_NOCLKOUT    ; INTOSCIO oscillator: I/O function on RA6/OSC2/CLKOUT pin, I/O function on RA7/OSC1/CLKIN
    cfg1&= _WDT_ON                ; WDT enabled
    cfg1&= _PWRTE_OFF             ; PWRT disabled
    cfg1&= _MCLRE_OFF             ; RE3/MCLR pin function is digital input, MCLR internally tied to VDD
    cfg1&= _CP_OFF                ; Program memory code protection is disabled
    cfg1&= _CPD_OFF               ; Data memory code protection is disabled
    cfg1&= _BOR_OFF               ; BOR disabled
    cfg1&= _IESO_ON               ; Internal/External Switchover mode is enabled
    cfg1&= _FCMEN_ON              ; Fail-Safe Clock Monitor is enabled
    cfg1&= _LVP_OFF               ; RB3 pin has digital I/O, HV on MCLR must be used for programming
    cfg1&= _DEBUG_OFF             ; In-Circuit Debugger disabled, RB6/ICSPCLK and RB7/ICSPDAT are general purpose I/O pins
      __CONFIG _CONFIG1, cfg1
    
    
    cfg2 = _BOR40V                ; Brown-out Reset set to 4.0V
    cfg2&= _WRT_OFF               ; Write protection off
      __CONFIG _CONFIG2, cfg2
    
    
    #ENDCONFIG
    
    
    'chip configs
    TRISA=%00000000  'SET A TO OUTPUT   1=input
    TRISC=%00001101   'set half C for in/out
    TRISB=%00011000   'set PortB to output
    ANSELH=%00000000   ' ADC OFF B
    ANSEL=%000000000 'configure PortA as digital except first 2
    ADCON1=%10000000  'adc justify
    OSCCON=%01110101  'SET FREQUENCY TO 8MHZ
    WPUB=%00000000    'turn off Pullups
    CM1CON0=0         'DISABLE COMPARATORS
    CM2CON0=0         'SAME HERE
    'CCP1CON=%01000000 ' configure pwm
    'PSTRCON=%00010110 'disable C pwm
    
    
    DEFINE OSC 8   
    DEFINE ADC_BITS 10
    DEFINE ADC_CLOCK 3
    DEFINE ADC_SAMPLEUS 50
    'lcd config
    pause 200
    ' Set LCD Data port 
    DEFINE LCD_DREG PORTC  
    DEFINE LCD_DBIT 4  
    DEFINE LCD_RSREG PORTB  
    DEFINE LCD_RSBIT 0  
    DEFINE LCD_EREG PORTB  
    DEFINE LCD_EBIT 1  
    DEFINE LCD_BITS 4  
    DEFINE LCD_LINES 2  
    DEFINE LCD_COMMANDUS 1500  
    DEFINE LCD_DATAUS 44
    define i2c_slow 1
    
    
    
    
    DPIN Var PORTA.2       ' I2C data pin
    CPIN Var PORTA.1       ' I2C clock pin
    B   Var word
    B1   Var byte
    B2   Var byte
    
    
    For B = 0 To 15 
      b1=99+b 
     I2CWRITE dpin,cpin,$A0,B,[b1]  
     Pause 10        '
    Next 
    pause 100
    
    
    mainloop:
    
    
       For B = 0 To 15   
         I2CREAD DPIN,CPIN,$A0,B,[b2]  
         lcdout $fe, $1, dec b, " ", dec b2 
         pause 1000
       Next 
     
       Goto mainloop
     
       End
    And funny thing happens - the returned value of B2, as shown on display, is 114! for all 16 locations.
    looks like 1st loop executed before writing to EEPROM ?

  27. #27
    Join Date
    Feb 2013
    Posts
    753

    Default Re: I2CRead & I2CWrite not working as expected

    Maybe read routine is faulty?

  28. #28
    Join Date
    Feb 2013
    Posts
    753

    Default Re: I2CRead & I2CWrite not working as expected

    yes it is read routine - it reads eeprom only once.

  29. #29
    Join Date
    May 2013
    Location
    australia
    Posts
    1,945

    Default Re: I2CRead & I2CWrite not working as expected

    works perfectly on simulator

    had to increase some delays for slow old lcd
    pause 1000
    ' Set LCD Data port
    DEFINE LCD_DREG PORTC
    DEFINE LCD_DBIT 4
    DEFINE LCD_RSREG PORTB
    DEFINE LCD_RSBIT 0
    DEFINE LCD_EREG PORTB
    DEFINE LCD_EBIT 1
    DEFINE LCD_BITS 4
    DEFINE LCD_LINES 2
    DEFINE LCD_COMMANDUS 2000
    DEFINE LCD_DATAUS 44
    lcdout $fe, $1, "ready " ;added to prove lcd working
    pause 1000


    Name:  sch.jpg
Views: 70
Size:  191.5 KB



    This is more entertaining than Free to Air TV

  30. #30
    Join Date
    Feb 2013
    Posts
    753

    Default Re: I2CRead & I2CWrite not working as expected

    I will use everything different - LCD, PIC, EEPROM and will check again...

  31. #31
    Join Date
    Nov 2019
    Posts
    20

    Default Re: I2CRead & I2CWrite not working as expected

    I have experienced an I2CREAD problem that might be related to this one. Coincidentally, I was using the DS3231 RTC device also, and it works fine with the PBP I2CREAD and I2CWRITE commands. My design also includes the Everset ES100 time code receiver (Canaduino), which responded correctly to I2CWRITE commands, but not to the I2CREAD command. I was able to enable the ES100 by writing to it, but when I tried to read its interrupt status, the ES100 clamped the I2C clock line after the I2CREAD's 3rd (read) byte.

    Referring to the lower scope screen in post #16 in this thread, it can be seen the PBP's I2CREAD command does not execute a full stop and start sequence between bytes 3 and 4 of the I2CREAD command. The ES100 requires (at the end of its 2nd byte) that the clock line be released high followed by the data line being released high (this is the stop sequence). Then, the 3rd byte starts with the data line being pulled low followed by the clock line being pulled low (the start sequence).

    In the traces below, it can be seen that start sequence at the beginning of the 4th byte is correct with the data going low followed by the clock going low, but it was not preceded by stop sequence. The data is released high followed by the clock released high rather than the reverse order.

    To solve the incompatibility of the PBP I2CREAD command with the ES100, I wrote a bit-banger routine that manipulates the clock and data lines in the proper sequences for start, stop, ack and nak, and combined these with the SHIFTOUT and SHIFTIN commands to send and receive data bytes.

    My interpretation of the I2C standard is that either a full start/stop or a restart sequence is permitted, with the restart having a slight speed advantage in time critical applications.

    The 24Cxx data sheet I checked seems to spec that only a restart sequence (that is, not a complete stop/start sequence) is required which the scope trace fulfills, but if you're really stumped on this, you might try implementing a full start/stop to see if this makes it act correctly.

    An alternate I2CREAD command addition to PBP that provides this full start/stop sequence would be nice to have.

    http://www.picbasic.co.uk/forum/atta...8&d=1633766449

Similar Threads

  1. I2cwrite - I2cread
    By savnik in forum mel PIC BASIC Pro
    Replies: 8
    Last Post: - 5th July 2006, 02:12
  2. Problem with I2Cread and I2CWRITE function
    By Tony85 in forum mel PIC BASIC Pro
    Replies: 7
    Last Post: - 6th June 2006, 21:03
  3. Problem with I2Cread and I2CWRITE function
    By Tony85 in forum mel PIC BASIC Pro
    Replies: 0
    Last Post: - 6th June 2006, 19:32
  4. PFC8583 Connection and I2Cwrite I2cread!
    By uludere72 in forum mel PIC BASIC Pro
    Replies: 11
    Last Post: - 27th February 2006, 14:32
  5. I2CWRITE and I2CREAD
    By Tomas in forum mel PIC BASIC Pro
    Replies: 1
    Last Post: - 23rd April 2004, 03:30

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts