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[mech962784]

dear rwskinner

thank you for your reply.
at least can you please give me a working code for generating CRC for modbus RTU (in PICBASIC Pro)

assuming that i have received from the HSERIN these byte

BYTe_1 BYTe_2 BYTe_3 BYTe_4 BYTe_5 BYTe_6 CRC1 CRC2

for example

01 03 00 00 00 0A C5 CD

how to calculate the CRC1 and CRC2

i am using this with PIC16F877A

Best Regards

[skimask]

dear rwskinner
thank you for your reply.
at least can you please give me a working code for generating CRC for modbus RTU (in PICBASIC Pro)
Best Regards

Did you look at your other thread? There's code already there...

[rwskinner]

Yep, it was in the thread that said "working Code"

Here is my method of CRC which I believe came from that thread ???
And my method of LRC which works but could be improved upon.

Notes:
CRC is a WORD, LRC is a Byte
Buf is an array that contains all the bytes.
Len is the number of bytes in the array and you set that depending on what your doing.
When Receiving messages LEN has to be adjusted to Exclude the CRC or LRC Bytes.



CalcCRC:
CRC16=$FFFF
For i = 0 to Len
CRC16=CRC16^Buf[i]
For j = 1 to 8
IF CRC16.Bit0 = 1 Then
CRC16=$A001^(CRC16>>1)
ELSE
CRC16=CRC16>>1
EndIf
Next j
Next i
Return




CalcLRC:
'Procedure Builds LRC value from bytes
LRC = 0
For i = 0 TO Len
LRC = LRC + Buf[i]
Next i
LRC = $100 - LRC
Return

[mech962784]

by the way: dear rwskinner

which company are you working for?
have you implemented the can or canopen protocol using the picbasic?
can you give me the specification of these two protocols?so i can do the implementation.

best regards

[JohnR]

Did you finally get a working solution for Modbus ?
I saw a lot of banter and pieces but I need a simple, complete source code in PicBasic and or assembly for PIC16F877A

If so would you share it or where can I get it

Thank You

[rwskinner]

There was actual working code in the links I posted above. These are not my sources but the code works.
Mine doesn't look anything like that however the CRC Routine was borrowed from it.

Also in the thread right next to this one called something like RS485 network