CFA633-RDI-KS datasheet(77/88 Pages) CRYSTAIFONTZ

77 / 88 page

Crystalfontz America, Inc.

Data Sheet Release Date 2012/02/21

www.crystalfontz.com

CFA633-RDI-KS LCD Module (Hardware v2.0 / Firmware s2v1)

February 2012

Page 77

End Sub

'My understanding of visual basic is very limited--however it appears that there is no way

'to initialize an array of structures. Nice language. Fast processors, lots of memory, big

'disks, and we fill them up with this . . this . . this . . STUFF.

Sub Initialize_CRC_Lookup_Table()

crcLookupTable(0).Lo = &H0

crcLookupTable(0).Hi = &H0

. . .

'For purposes of brevity in this data sheet, I have removed 251 entries of this table, the

'full source is available in our forum:

'http://www.crystalfontz.com/forum/showthread.php?postid=9921#post9921

. . .

crcLookupTable(255).Lo = &H78

crcLookupTable(255).Hi = &HF

End Sub

'This function returns the CRC of the array at data for length positions

Private Function Get_Crc(ByRef data() As Byte, ByVal length As Integer) As WORD

Dim Index As Integer

Dim Table_Index As Integer

Dim newCrc As WORD

newCrc.Lo = &HFF

newCrc.Hi = &HFF

For Index = 0 To length - 1

'exclusive-or the input byte with the low-order byte of the CRC register

'to get an index into crcLookupTable

Table_Index = newCrc.Lo Xor data(Index)

'shift the CRC register eight bits to the right

newCrc.Lo = newCrc.Hi

newCrc.Hi = 0

' exclusive-or the CRC register with the contents of Table at Table_Index

newCrc.Lo = newCrc.Lo Xor crcLookupTable(Table_Index).Lo

newCrc.Hi = newCrc.Hi Xor crcLookupTable(Table_Index).Hi

Next Index

'Invert & return newCrc

Get_Crc.Lo = newCrc.Lo Xor &HFF

Get_Crc.Hi = newCrc.Hi Xor &HFF

End Function

Private Sub Send_Packet(ByRef packet As PACKET_STRUCT)

Dim Index As Integer

'Need to put the whole packet into a linear array

'since you can’t do type overrides. VB, gotta love it.

Dim linear_array(26) As Byte

linear_array(0) = packet.command

linear_array(1) = packet.data_length

For Index = 0 To packet.data_length - 1

linear_array(Index + 2) = packet.data(Index)

Next Index

packet.crc = Get_Crc(linear_array, packet.data_length + 2)

'Might as well move the CRC into the linear array too

linear_array(packet.data_length + 2) = packet.crc.Lo

linear_array(packet.data_length + 3) = packet.crc.Hi

'Now a simple loop can dump it out the port.

For Index = 0 To packet.data_length + 3

MSComm.Output = Chr(linear_array(Index))

Next Index

End Sub

Algorithm 5: “Java” Table Implementation

This code was posted in our forum by user “norm” as a working example of a Java CRC calculation.

public class CRC16 extends Object

{

public static void main(String[] args)

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