I2c write&read [Archive] - MEL PICBASIC Forum

MINHLE

- 3rd January 2010, 21:03

Hi every one,
i ahce a problem with writing and reading using I2C WRITE...

thansk for any help,
-----------------

here is the connection:

pic16f628: porta.6 and 7 are SDA & SCL

24lc256 (8 bit EEPROM): A0,1,2,3,4 and WP: ground
SDA &SCL connected 10k to 5V...
------------------------
;the program:

CMCON = 1
TRISA = %11000000 ; set port A6,7 to input (SDA & SLC)
TRISB = 0
DPin var PORTA.6 ' I2C data pin
Cpin var PORTA.7 ' I2C clock pin

I var byte
S VAR BYTE
b1 var byte
k var byte

B0 var byte

i = 0
b0 = 0

while b0 != $ff
lookup I, [$3F,$48,$48,$48,$3F,$3F,$00,$ff],B0 ;put a value into
;B0
I2CWRITE DPIN,CPIN,$A0,i,[B0] ' Write B0 to address I

Pause 10 ' Delay 10ms after each write
i = i+1 ' increase the address by 1
wend
loop:
;reading process
b1 = 0 ; clear b1
while b1 !=$ff
I2CREAD DPIN,CPIN,$A1,i,[B1]

FOR K = 0 TO 63 ; scan for 64 times
CALL RESET
PORTB = b1
CALL DELAY

NEXT K
i = i +1
wend
goto loop
end
RESET: PORTA.1 = 1 ;RESET 4017
@NOP
PORTA.1 = 0
RETURN

DELAY: pause 10
portb = 0 ; reset portb
porta.0 = 1 ; clock the 4017
@nop
porta.0 = 0
return

Gusse

- 3rd January 2010, 23:52

Read this thread: I2CRead & I2CWrite not working as expected (http://www.picbasic.co.uk/forum/showthread.php?t=587)

BR,
-Gusse-

MINHLE

- 4th January 2010, 00:49

thanks for your words,

i checked but it is ok, the device is 8 bit size. and the address is variable..
all are defined by BYTE.
i.e i = 0 to 10 ;(i : location in the EEPROM)

thanks agains
MInhle

Gusse

- 4th January 2010, 08:20

Hi MInhle,

Check once more the thread and do like Melanie advices!

Define I2CDevice as a BYTE, not a constant.
Define I2CAddress as a WORD (your EEPROM is >16k and therefore variable must be a word)

Example:
I2CWrite SDA,SCL,I2CDevice,I2CAddress,[DataA]

BR,
-Gusse-

Melanie

- 4th January 2010, 11:18

10K is also a little high... drop it by at least half to say 4K7.

MINHLE

- 4th January 2010, 14:23

Hello All,

the deviec is 16f628. the OSC 20Mhz (internal OSC, so R is ~10k-12K)
and the 24lc256 is BYTE SIZE. (32K X8 BIT)
the address is variable.

i will change to 4.7k and redefine eeprom address.

however the fuse defined: (work well )

OSC: INTRO CLOCKOUT
MCLR: INPUT PIN
(all other defined in the fuse window: marain unchange)

thank for all

regards,

Gusse

- 4th January 2010, 14:43

Hi MInhle,

Check the link and see the table.
I2CRead/I2CWrite (http://melabs.com/resources/pbpmanual/5_30-5_31.htm) part of PicBasic Pro manual

What is address size for over 24LC16 (2K bytes) devices?
:D

BR,
-Gusse-

MINHLE

- 4th January 2010, 17:45

thank Gusse,

i replaced data address (I: in this case) by WORD . . and/or change R from 10K to 6K. ..it doesnot work.

(in the data sheet of 24lc256 dooesnot mention anything data address.

VOLTAGE drop across: R_SCL (10K or 6K) : ~5V (unchanged)
R_SDA (10K or 6K): ~2.5V

!! is it possible the EEPROM: DEATH??

Gusse

- 4th January 2010, 19:55

Hi MInhle,

If you are running with internal oscillator then speed is 4MHz, not 20MHz. Also you should tell that to compiler.

14.2.6 INTERNAL 4 MHZ OSCILLATOR
The internal RC oscillator provides a fixed 4 MHz
(nominal) system clock at VDD = 5V and 25°C, see
“Electrical Specifications” section for information on
variation over voltage and temperature.

DEFINE OSC 4

OSC: INTRO CLOCKOUT

14.2.7 CLKOUT
The PIC16F62X can be configured to provide a clock
out signal by programming the configuration word. The
oscillator frequency, divided by 4 can be used for test
purposes or to synchronize other logic.

CLKOUT is RA6, which is also your I2C data pin. Disable CLKOUT or change I2C data pin to other IO.

If you are not using comparator then disable those.

CMCON = 7

I hope these modifications will bring up some life to your EEPROM interface.

BR,
-Gusse-

MINHLE

- 4th January 2010, 20:41

hello GUSSE,

i got a BONUS now. the led is on (pin2 only) and flash

i lookk for error in teh program and let u knoow later

thanks for your help

MINHLE

- 4th January 2010, 23:52

HI Gusse,

the modifications were made.
as indicated.

defined OSC 4 ;no effect: ( INTCLOUT is set in the fuse window)
SDA PORTA.3
SCL PORRT.4
......

R_SDA & R_SCL: 4.5k
a led on portb flashed is due to error that i cannot see where it comes from

not write nor read. i assume EEPROM???

Gusse

- 5th January 2010, 09:21

Hi MInhle,

Below is very simple I2C write and read test script.

<code>CMCON = 7
TRISA = %11000000
TRISB = %00000000

SDA VAR PortA.3
SCL VAR PortA.4
LED VAR PortB.0 'Indicator LED (change if needed)

I2CDeviceEEprom VAR BYTE
I2CAddressEEprom VAR WORD
TEMP1 VAR BYTE
TEMP2 VAR BYTE

I2CDeviceEEprom=$A0 'DeviceID 10100000 = $A0 = %1010 A2=0, A1=0, A0=0 R/W=0

DEFINE OSC 4

Main:
I2CAddressEEprom = 0
TEMP1 = 1
GOSUB Write_I2C
PAUSE 10
GOSUB Read_I2C
IF TEMP1 = TEMP2 THEN
HIGH LED 'If OK then 0.5s LED blink
PAUSE 500
LOW LED
ELSE
HIGH LED 'If FAIL then 2s LED blink
PAUSE 2000
LOW LED
ENDIF
GOTO Main

Write_I2C:
I2CWRITE SDA, SCL, I2CDeviceEEprom, I2CAddressEEprom,[ TEMP1 ]
RETURN

Read_I2C:
I2CREAD SDA, SCL, I2CDeviceEEprom, I2CAddressEEprom,[ TEMP2 ]
RETURN

END
</code>
If write and read are successfully executed then LED will blink for 0.5s.
2s LED blink will be an indication of fail.

BR,
-Gusse-

MINHLE

- 5th January 2010, 18:00

hello Gusse,

I copy you program. run ---> the light is solid.,

i tr to put direcly data into EEProm, the out put is whatever,,,

i.e.

i = 0 ; data address
b0 = $2a ; data to be stored

i2cwrite .......... i, [b0]

b0 = 0
i2cread .........i,[b0]

run ----> whatever... output (BONUS ONLY)

i have to replace the EEPROm
thanks for your time

regards,

Gusse

- 5th January 2010, 18:20

Hi,

Sorry, I had one bug there. One pause missing.

<code>CMCON = 7
TRISA = %11000000
TRISB = %00000000

SDA VAR PortA.3
SCL VAR PortA.4
LED VAR PortB.0 'Indicator LED (change if needed)

I2CDeviceEEprom VAR BYTE
I2CAddressEEprom VAR WORD
TEMP1 VAR BYTE
TEMP2 VAR BYTE

I2CDeviceEEprom=$A0 'DeviceID 10100000 = $A0 = %1010 A2=0, A1=0, A0=0 R/W=0

DEFINE OSC 4

Main:
I2CAddressEEprom = 0
TEMP1 = 1
GOSUB Write_I2C
PAUSE 10
GOSUB Read_I2C
IF TEMP1 = TEMP2 THEN
HIGH LED 'If OK then 0.5s LED blink
PAUSE 500
LOW LED
ELSE
HIGH LED 'If FAIL then 2s LED blink
PAUSE 2000
LOW LED
ENDIF
PAUSE 1000 'PAUSE ADDED
GOTO Main

Write_I2C:
I2CWRITE SDA, SCL, I2CDeviceEEprom, I2CAddressEEprom,[ TEMP1 ]
RETURN

Read_I2C:
I2CREAD SDA, SCL, I2CDeviceEEprom, I2CAddressEEprom,[ TEMP2 ]
RETURN

END
</code>
Now it will blink.

BR,
-Gusse-

MINHLE

- 5th January 2010, 23:00

Hello Gusse,

thanks for your help,

the eeprom is wrong. I replace a another one. it is ok now.

and the R_SCL and R_SDA are either 13K or 3,3 k the light intensity and frequency does not change (by naked eyes)

thanks again
Minh le

MINHLE

- 5th January 2010, 23:13

Hello Gusse,
actually it is not necessary to " define OSC 4" it is defined in fuse ("INTCLOUT.."

the 24lc256 it takes only 5ms to write

thanks
regards