I2C with 16F628A mystery

[lilimike]

Thank you Peter,

I understand the first part of your response but not sure about the second part:

Now the PBP manual states "The Address size sent (byte or word) is determined by the size of the variable that is used. If a byte-sized variable is used for the Address, an 8-bit address is sent. If a word-sized variable is used, a 16-bit address is sent. Be sure to use the proper sized variable for the device you wish to communicate with."

I suspect this is in fact not correct and looking at the assembler code that PBP generates, in fact I2CWRITE seems to send a word, using I2CAddr, I2CAddr2 as the (word) address in my example, or the case of your code, actually I2CAddr, I2CDevice (=$A0) which is I suspect somewhere other than you intended in memory!

I will continue to read it over and over, some times it takes me a few times to understand.

Now again I am running into some mystery and I wish I could understand better...

If I run this code:

i2cdevice =$A0
for i2caddr = 0 to 2048 step 16
    i2cwrite d1,d2,i2cdevice,i2caddr,[$01]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$01]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$01]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$3c]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$3c]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$3c]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$3c]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$3c]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$3c]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$08]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$08]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$08]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$21]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$21]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$21]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[$ff]:pause 10
next

Then I read the EPROM with Ponyprog and observed everything as expected.


Then I rewrote my code by changing:

for i2caddr = 0 to 2048 step 16

to

for i2caddr = 0 to 1024 step 16

and the 3 first line I replaced $01 by $ff.

I was expecting to see half of the memory filled with my changes but it got filled all the way to address $7FF:


The more I test the more I get confused!

Mike

[FinchPJ]

Actually I was wrong about the Addressing - I hadn't noticed you were using a 24C16 - I normally use larger chips - in fact the 24C16 needs a byte for the address. Unfortunately the addressing you require is a little more complex - the 2K memory is organised in 8 x 256 byte blocks and the A10, A9, A8 are conveyed as the lower 3,2,1 bits of the Control byte, and A7-0 in the Address byte - a rewrite of your addressing is needed!
Control Byte: 1010XXX0 where XXX are the high order 3 bits of the address
Address Byte: XXXXXXXX = A7-0
You will need to create the Control byte for each successive write. Get back to me if you need any more help.
Peter

[lilimike]

Ok so maybe I need more help.
There is obviously something I don't understand.

Looking at the 24CL16 datasheet:


Based on this I changed the address to word and my understanding is:
Control byte = 1010 000 0 = $A0
I want to write $aa at address $400 so I wrote this code:

i2cdevice =$A0
i2caddr = $400

    i2cwrite d1,d2,i2cdevice,i2caddr,[$aa]:pause 10

I was expecting to see only address $400 showing value $aa but this is the result:


the value $aa is now showing at address $004 and at every next 16 locations all the way to 2048.

???

Mike

[FinchPJ]

I suggest you use a data array to send your bytes, and then you need to construct the ControlByte and address as in this example:

Dat         VAR byte[16]
i           var word
j           var Byte
SDA         var PORTA.2
SCL         VAR PORTA.3
CntrB       var Byte
Addr        var byte
    for i = 0 to 15
        lookup i, [$01,$01,$01,$3c,$3c,$3c,$3c,$3c,$3c,$08,$08,$08,$21,$21,$21,$FF], j
        Dat[i] = j
    next
    for i = 0 to $7F0 step 16  'End at 2048-16 = $7F0
        CntrB = %10100000
        CntrB.3 = i.10
        CntrB.2 = i.9
        CntrB.1 = i.8
        Addr = i.lowbyte
        i2cwrite SDA,SCL,CntrB,Addr,[str Dat\16]
        pause 10
    next

Peter

[lilimike]

ok I have created a new file and inserted your code with some of my code required for access to the EEPROM but when I run this code nothing gets written to the chip.

This is the complete code:

@ __config _INTOSC_OSC_NOCLKOUT & _WDT_OFF & _MCLRE_ON & _LVP_OFF & _CP_OFF
clear
DEFINE OSC 4
TRISB = %00001000           
CMCON = 7                   ; Disable comparator
OPTION_REG = 0

Activate    var PORTB.2     ; 1 = access eeprom / 0 = normal operation
GO          VAR PORTB.3     ; Start switch
OK          VAR PORTB.4     ; Green LED
NOTOK       var PORTB.5     ; Red LED

Dat         VAR byte[16]
i           var word
j           var Byte
SDA         var PORTA.2
SCL         VAR PORTA.3
CntrB       var Byte
Addr        var byte

activate = 1



    for i = 0 to 15
        lookup i, [$01,$01,$01,$3c,$3c,$3c,$3c,$3c,$3c,$08,$08,$08,$21,$21,$21,$FF], j
        Dat[i] = j
    next
    for i = 0 to $7F0 step 16  'End at 2048-16 = $7F0
        CntrB = %10100000
        CntrB.3 = i.10
        CntrB.2 = i.9
        CntrB.1 = i.8
        Addr = i.lowbyte
        i2cwrite SDA,SCL,CntrB,Addr,[str Dat\16]
        pause 10
    next
activate = 0   
end

I've been struggling with this almost nonstop for a couple of days and I believe that either I think I am working with a 24LC16 chip and it is not or I have a hardware issue. The EEPROM chip is not visually accessible but my PonyProg application is detecting it as"2416" - Device type "2402-16"
This is my hardware and I ruled out any discrepancies between my drawing and actual PCB:


Thanks for your time,

Mike

[lilimike]

sorry, Your code did write to the chip, what I did was to zero out the complete memory using this code:

I2CAddr = $0
I2CDevice = $A0
    i2cwrite d1,d2,i2cdevice,i2caddr,[0]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[0]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[0]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[0]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[0]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[0]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[0]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[0]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[0]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[0]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[0]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[0]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[0]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[0]:i2caddr = i2caddr + 1:pause 10
    i2cwrite d1,d2,i2cdevice,i2caddr,[0]:i2caddr = i2caddr + 1:pause 10

Then I ran your code (as previous post) and I see that it wrote value FF on every 16th location from memory 0 to 2032 as such:


Mike

[FinchPJ]

I am not familiar with PonyProg, are you using the SI-Prog baseboard hardware and the I²CBus eeprom adapter - I note that the adaptor does not have any pullup resistors on SDA and SCL and the baseboard does not provide these either - You have implemented the R2/R3 4K7 pullups shown on your schematic, havent you?? I have had many frustrating experiences with I2C Memory chips instantly solved by a pair of pull up resistors.

Failing this, I dont understand why the memory chip is visually inaccessible, but these results suggest you may not be dealing with a 24C16 chip - other chips may need different addressing.