I2C Code for the BS2, BS2e, and BS2sx

basejumper9 · 2007-03-20 19:11

So I think I'm close now here is what I have for just reading the eeprom:

' -----[noparse][[/noparse] I/O Definitions ]-------------------------------------------------

SDA             PIN     5                       ' I2C serial data line
SCL             PIN     4                       ' I2C serial clock line


' -----[noparse][[/noparse] Constants ]-------------------------------------------------------

Ack             CON     0                       ' acknowledge bit
Nak             CON     1                       ' no ack bit

' -----[noparse][[/noparse] Variables ]-------------------------------------------------------

slvAddr         VAR     Byte                    ' slave address
devNum          VAR     Nib                     ' device number (0 - 7)
addrLen         VAR     Nib                     ' 0, 1 or 2
devAddr         VAR     Word                    ' address in device

i2cData         VAR     Byte                    ' data to/from device
i2cWork         VAR     Byte                    ' work byte for TX routine
i2cAck          VAR     Bit                     ' Ack bit from device

location        VAR     Byte



' -----[noparse][[/noparse] EEPROM Data ]-----------------------------------------------------


' -----[noparse][[/noparse] Initialization ]--------------------------------------------------

Reset:
  #IF ($stamp >= BS2P) #THEN
    #ERROR "Use I2COUT and I2CIN!"
  #ENDIF

  devNum = 0                                    ' device address %000
  slvAddr = (location) << 1
  addrLen = 0                                   ' no internal addresses

  DEBUG CLS,
        "24C11 Demo", CR                         ' setup output screen


' -----[noparse][[/noparse] Program Code ]----------------------------------------------------

Main:

    FOR location = 0 TO 127
      slvAddr = (location) << 1
      GOSUB Read_Byte
      DEBUG BIN8 slvAddr, " "
      DEBUG IHEX i2cData,CR
      'PAUSE 100
    NEXT


  END


' -----[noparse][[/noparse] Subroutines ]-----------------------------------------------------


' -----[noparse][[/noparse] High Level I2C Subroutines]---------------------------------------
' Random location read
' -- pass device slave address in "slvAddr"
' -- pass address bytes (0, 1 or 2) in "addrLen"
' -- register address passed in "devAddr"
' -- data byte read is returned in "i2cData"

Read_Byte:
  GOSUB I2C_Start                               ' send Start
  i2cWork = slvAddr | %00000001                 ' send slave ID (read)
  GOSUB I2C_TX_Byte
  GOSUB I2C_RX_Byte_Nak
  GOSUB I2C_Stop
  i2cData = i2cWork
  RETURN


' -----[noparse][[/noparse] Low Level I2C Subroutines]----------------------------------------

' *** Start Sequence ***

I2C_Start:                                      ' I2C start bit sequence
  INPUT SDA
  INPUT SCL
  LOW SDA

Clock_Hold:
  DO : LOOP UNTIL (SCL = 1)                     ' wait for clock release
  RETURN


' *** Transmit Byte ***

I2C_TX_Byte:
  SHIFTOUT SDA, SCL, MSBFIRST, [noparse][[/noparse]i2cWork\8]      ' send byte to device
  SHIFTIN SDA, SCL, MSBPRE, [noparse][[/noparse]i2cAck\1]          ' get acknowledge bit
  RETURN


' *** Receive Byte ***

I2C_RX_Byte_Nak:
  i2cAck = Nak                                  ' no Ack = high
  GOTO I2C_RX

I2C_RX_Byte:
  i2cAck = Ack                                  ' Ack = low

I2C_RX:
  SHIFTIN SDA, SCL, MSBPRE, [noparse][[/noparse]i2cWork\8]         ' get byte from device
  SHIFTOUT SDA, SCL, LSBFIRST, [noparse][[/noparse]i2cAck\1]       ' send ack or nak
  RETURN


' *** Stop Sequence ***

I2C_Stop:                                       ' I2C stop bit sequence
  LOW SDA
  INPUT SCL
  INPUT SDA
  RETURN

Everything looks right to me unless I missed something, any ideas?

Post Edited (basejumper9) : 3/20/2007 7:16:55 PM GMT

basejumper9 · 2007-03-25 18:14

For some reason the eeprom does seem to respond right, it seems like no matter what I do I only get an $ff/ 11111111 back unless I'm missing something major in the literature it should go like this for a read cycle:
1. I2C start
2. Master sends a 7 bit address (0000000 through 1111111) with the 8th bit being read/write which would be a 1 cause we are reading
3. Slave sends an Ack which is pulling the line low
4. Slave sends a byte back
5. Master keeps the line high to signal no Ack
6. Master sends a stop

Questions:
Is all that above right? Am I addressing the eeprom right? an ideas on where my code is wrong?

GeisteskrankerAlkoholiker · 2009-01-03 00:42

I like to communicate with an ADC MAX127 over I2C.

I need to write an Slave_Byte and a Control_Byte to program it and I need to read it Like Slave_byte, Data_byte1, Data_byte2.

How should I write this program???

I2COUT SDA, Slave_Byte, [noparse][[/noparse]Control_Byte]

I2CIN SDA, Slave_Byte, [noparse][[/noparse]result1, result2] ??????

Need help!!!!

$WMc% · 2009-01-03 03:09

Mr.Jon Williams

Thank You for the EEPROM I2C Applications. This is A great help to Me. I was gonna post a "new topic" on this, And Boom their it was on the forum.

Its Your "I'll show You" approach, That I like most. From this I learn the most!!!...Your REM statements tell Me whats going on in the code.I learn from this and advance to higher levels of programing code with the BS2 series. Thanks Again

__________________$WMc%_________________Happy New Year

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
The Truth is out there·········································· E=$WMc%2

Post Edited ($WMc%) : 1/3/2009 6:38:39 AM GMT

I2C Code for the BS2, BS2e, and BS2sx

Comments