Adaptation of libraries from Swordfish for Firewing

[demanik]

Prompt as it is correct to redo read and write procedures a string from Swordfish EEPROM library

Code: Select all

sub ReadItem(byref pStr as string)
   dim StrPtr as POSTINC0
   FSR0 = @pStr
   do
      StrPtr = ReadByte(Address)
   loop until char(EEDATA) = null
end sub

sub WriteItem(pValue as string)
   dim StrPtr as POSTINC0
   FSR0 = @pValue
   do
      WriteByte(Address,StrPtr)
   loop until char(EEDATA) = null
end sub


thanks

[David John Barker]

You could use something like

Code: Select all

sub ReadItem(byref pStr as string)
   dim StrPtr as POSTINC0
   FSR0 = addressof(pStr)
   do
      StrPtr = ReadByte(Address)
   loop until cchar(EEDATA) = nothing
end sub

sub WriteItem(pValue as string)
   dim StrPtr as POSTINC0
   FSR0 = addressof(pValue)
   do
      WriteByte(Address,StrPtr)
   loop until cchar(EEDATA) = nothing
end sub

However, when using Firewing it's a good idea to get used to using "generic" pointer references. For example, you could write the code like this:

Code: Select all

Sub ReadItem(ByRef text As String)
   addr0 = AddressOf(text)
   Do
      *(addr0+) = ReadByte(Address)
   Loop Until CChar(EEDATA) = Nothing
End Sub

Sub WriteItem(text As String)
   addr0 = AddressOf(text)
   Do
      WriteByte(Address,*(addr0+))
   Loop Until CChar(EEDATA) = Nothing
End Sub

Note the use of "addr0". This is a portable pointer reference which will work with PIC18, PIC24 and PIC32 targets. All of the Firewing libraries use this technique so they can be built using 8, 16 or 32 bit compilers. For example, if you look at the "strings" module (click on the library in the explorer window) you will see something like this:

Code: Select all

Public Function Len(ByVal value As String) As Byte
   addr0 = AddressOf(value)
   Len = 0
   While *(addr0+) <> 0
      Len += 1
   End While
End Function

which determines the length of a given string. If the above function had used "FSR0" and "POSTINC0" it could only ever be built for PIC18 devices. There is more of a discussion here:

http://www.firewing.info/forum/viewtopic.php?f=7&t=39&p=190