code conversion

Hi All

i have a checksum calculation routine that works in Visual Basic i am trying to convert to PicBasic.

the source for the checksum are the first 32 locations in a AT93C46 EEprom (16 bit mode).

i am sure i am doing something stupid but all i get with the Picversion is FFFF,FFFF(sometimes FFFF,7FFF) independent of the eeprom contents.
after spending 5 days on this i hope some fresh eyes will spot my error.

thanks in advance

dj.lambert


VB code:

<code>
Private Sub Checksumme(dat$)
' Checksumme berechnen
Dim x, d, cs$
adrx1 = 1: adrx2 = 31: GoSub summe1x
cs$ = Right$("00" + Hex$(summe), 2)
adrx1 = 9: adrx2 = 18: GoSub summe1x
cs$ = Right$("00" + Hex$(summe), 2) + cs$
'Stop
cs = cs$

Label5.Caption = "Checksum : " & cs
If writecsum = True Then
WriteCheckSum cs$
'Stop
End If
writecsum = False
Exit Sub

summe1x:

summe = &HA5
For x = adrx1 To adrx2 Step 1
d = Mid$(dat$, x * 5 + 1, 4)
'Stop
d = Val("&H" + Mid$(dat$, x * 5 + 1, 4))
summe = (summe + (d And &HFF)) And &HFF
If (summe And 1) = 1 Then
summe = summe \ 2 + &H80
Else
summe = summe \ 2
End If
summe = (summe + (d And &HFF00) \ &H100) And &HFF
If (summe And 1) = 1 Then
summe = summe \ 2 + &H80
Else
summe = summe \ 2
End If

Next
summe = summe And &HFF

Return

End Sub

</code>

PicBasic code:

<code>
CheckSum:
adrx1 = 1
adrx2 = 31
gosub summe1x

adrx1 = 9
adrx2 = 18
gosub summe1x

return


Summe1X:
summe = $A5
for addr = adrx1 to adrx2 step 1
d= b3a(addr)
temp=d
serout2 PortB.1, 84, [hex summe, hex d, 10,13]
summe = (summe + (templo)) and $FF
serout2 PortB.1, 84, [hex summe, 10, 13]
if (summe and 1) = 1 then
summe = summe / 2 + $80
else
summe = summe / 2
endif
serout2 PortB.1, 84, [hex summe, 10, 13]
summe = (summe + (temphi) / $100) and $FF
serout2 PortB.1, 84, [hex summe, 10, 13]
if (summe and 1) = 1 then
summe = summe / 2 + $80
else
summe = summe / 2
endif
serout2 PortB.1, 84, [hex summe, 10, 13]

next
serout2 PortB.1, 84, [hex summe, 10, 13]
summe = summe and $FF
serout2 PortB.1, 84, [hex summe, 10, 13]




return



</code>
variable declarations for PB:

B3A var word(32)
temp var word
tempLo var temp.byte0
tempHi var temp.byte1
adrx1 var byte
adrx2 var byte
CheckSumme var word
Summe var word
d var word

Some observations

1 - the VB code is reading 4 hex characters from locations (x*5 + 1) at a time. This is assuming VB is set to "option base 1"
so, for index 1 it reads from 6, for index 2 it reads from 11 etc
Your PB code is not doing that

2 - the VB code is expecting HEX characters and converts them to a value using the val("&H" ......) operation.
Your PB code is treating the values in the EEPROM as proper word values which they are not

Hi Jerson

thanks for the reply

the 1st point i have removed the lines for that and forgot to put them back in (i removed them to make it a bit simpler to follow).

the second point is i think where the problem with the conversion is occurring.
i get compile errors if i try to force the variables to hex.

dj.lambert

Hi Dj

You do not need to force the values to Hex, instead you need to convert the HEX values to word. Since PBP does not support a function like VB does, you need to build this code. A simple routine to convert a hex character to byte would be

Code:

---

' expects a HEX character with capitalized A-F values
Hex2Bin:
    Hexchar = Hexchar - "0"          ' remove the value of ascii 0 (30H)
    if Hexchar > 9 then  Hexchar = Hexchar - 7  ' convert A-F to 0a-0Fh
    return

---

Now, you would do this 4 times once for each nibble in the word you are converting and get your Hex word like this

Code:

---

  WordVal = 0                              ' start with a val of 0
  read a hex character to HexChar
  gosub Hex2Bin
  WordVal = WordVal * 16 + HexChar
  read a hex character to HexChar
  gosub Hex2Bin
  WordVal = WordVal * 16 + HexChar
  read a hex character to HexChar
  gosub Hex2Bin
  WordVal = WordVal * 16 + HexChar
  read a hex character to HexChar
  gosub Hex2Bin
  WordVal = WordVal * 16 + HexChar

---

Now, WordVal would contain the 16 bit representation of the 4 character Hex String