24LC640

SwordfishUser.24LC640 History

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October 04, 2007, at 11:45 AM by David Barker -
Added line 16:
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October 04, 2007, at 11:44 AM by David Barker -
Added lines 10-12:
// use software or hardware SPI...
#option USE_SOFTWARE_SPI = false
Added lines 16-24:
#if USE_SOFTWARE_SPI
#option SSPI_SCK = PORTC.3
#option SSPI_SDI = PORTC.4
#option SSPI_SDO = PORTC.5
Include "SSPI.bas"
Dim
  SPIWriteByte As SSPI.WriteByte,
  SPIReadByte As SSPI.ReadByte
#else
Changed lines 26-30 from:
to:
Dim
  SPIWriteByte As SPI.WriteByte,
  SPIReadByte As SPI.ReadByte
#endif
Changed line 48 from:
   SPI.WriteByte(cmdWriteEnable)      // enable writes
to:
   SPIWriteByte(cmdWriteEnable)      // enable writes
Changed lines 58-59 from:
     SPI.WriteByte(cmdReadStatus)
      WriteStatus = SPI.ReadByte
to:
     SPIWriteByte(cmdReadStatus)
      WriteStatus = SPIReadByte
Changed lines 67-70 from:
   SPI.WriteByte(cmdRead)            // read command
  SPI.WriteByte(pAddress.Byte1)      // write address (high byte)
  SPI.WriteByte(pAddress.Byte0)      // write address (low byte)
  Result = SPI.ReadByte              // read the data
to:
   SPIWriteByte(cmdRead)            // read command
  SPIWriteByte(pAddress.Byte1)      // write address (high byte)
  SPIWriteByte(pAddress.Byte0)      // write address (low byte)
  Result = SPIReadByte              // read the data
Changed lines 79-82 from:
   SPI.WriteByte(cmdWrite)            // write command
  SPI.WriteByte(pAddress.Byte1)      // write address (high byte)
  SPI.WriteByte(pAddress.Byte0)      // write address (low byte)
  SPI.WriteByte(pData)              // write the data
to:
   SPIWriteByte(cmdWrite)            // write command
  SPIWriteByte(pAddress.Byte1)      // write address (high byte)
  SPIWriteByte(pAddress.Byte0)      // write address (low byte)
  SPIWriteByte(pData)              // write the data
Changed lines 90-91 from:
   SPI.WriteByte(cmdReadStatus)
  Result = Boolean(Not SPI.ReadByte)
to:
   SPIWriteByte(cmdReadStatus)
  Result = Boolean(Not SPIReadByte)
Added lines 101-104:
#if USE_SOFTWARE_SPI
SSPI.Initialize
SSPI.SetClock(spiIdleHigh)
#else
Added line 109:
#endif
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October 04, 2007, at 11:23 AM by David Barker -
Added lines 1-109:
Swordfish already includes a module to read and write data to a 24LC640 EEPROM - see the sample samples folder. However, this little bit of code strips away the various module layers so you can see how it's done. It should be very easy to modify and add new functionality.

The following code implements a WaitFor() routine. This is very useful if you want to (a) wait until writes are enabled on the device and (b) wait for write completion. The latter call is very useful and removes the need for an explicit delay after each write. The code also implements an Available() function, which checks to see if the SPI EEPROM is ready to receive commands or not.

=code [=
// device and clock...
Device = 18F452
Clock = 20

// import modules...
Include "usart.bas"
Include "convert.bas"
Include "SPI.bas"

// SPI EEPROM constants...
Const
  cmdRead = $03,
  cmdWrite = $02,
  cmdWriteEnable = $06,
  cmdWriteDisable = $04,
  cmdReadStatus = $05,
  cmdWriteStatus = $01,
  stWriteEnabled = $02,
  stWriteFinished = $00

// chip select pin... 
Dim CS As PORTC.1

// enable writes...
Sub EnableWrite()
  CS = 0                              // chip select on
  SPI.WriteByte(cmdWriteEnable)      // enable writes
  CS = 1                              // chip select off
End Sub

// wait for command acknowledge - parameters may be stWriteEnabled
// and stWriteFinished
Sub WaitFor(pStatus As Byte)
  Dim WriteStatus As Byte
  Repeat
      CS = 0
      SPI.WriteByte(cmdReadStatus)
      WriteStatus = SPI.ReadByte
      CS = 1
  Until WriteStatus = pStatus
End Sub

// Read a byte...
Function ReadByte(pAddress As Word) As Byte
  CS = 0                            // chip select on
  SPI.WriteByte(cmdRead)            // read command
  SPI.WriteByte(pAddress.Byte1)      // write address (high byte)
  SPI.WriteByte(pAddress.Byte0)      // write address (low byte)
  Result = SPI.ReadByte              // read the data
  CS = 1                            // chip select off
End Function

// Write a byte...
Sub WriteByte(pAddress As Word, pData As Byte)
  EnableWrite                        // enable writes
  WaitFor(stWriteEnabled)            // wait for write enable flag
  CS = 0                            // chip select on
  SPI.WriteByte(cmdWrite)            // write command
  SPI.WriteByte(pAddress.Byte1)      // write address (high byte)
  SPI.WriteByte(pAddress.Byte0)      // write address (low byte)
  SPI.WriteByte(pData)              // write the data
  CS = 1                            // chip select off
  WaitFor(stWriteFinished)          // wait for write completion
End Sub

// see if the device is ready to accept commands...
Function Available() As Boolean
  CS = 0
  SPI.WriteByte(cmdReadStatus)
  Result = Boolean(Not SPI.ReadByte)
  CS = 1
End Function

// local variables...
Dim Address As Word
Dim Index As Byte

// initialise...
SetBaudrate(br115200)
SPI.SetAsMaster(spiOscDiv64)
SPI.SetClock(spiIdleHigh, spiRisingEdge)
SPI.SetSample(spiSampleEnd)
SPI.Enabled = true
Output(CS)
 
// write and read back 10 numbers to SPI EEPROM... 
If Not Available Then
  USART.Write("NOT FOUND",13,10)
Else 
  USART.Write("Available, writing data...",13,10)
  Index = 0
  For Address = 0 To 10
      WriteByte(Address, Index)
      Inc(Index, 10)
  Next

  USART.Write("Reading data...",13,10)
  For Address = 0 To 10
      Index = ReadByte(Address)
      USART.Write(DecToStr(Index),13,10)
      DelayMS(500)
  Next
EndIf
=]
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