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simplified message handling, switch from XOR checksum to CRC8 with polynomial 0x97.

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0x97 allows for detection of all 1-3 bit errors in a message of up to
119 bytes
(see https://www.faa.gov/aircraft/air_cert/design_approvals/air_software/media/TC-14-49.pdf)
This commit is contained in:
Martin Preuss
2023-04-07 23:22:40 +02:00
parent 090122a192
commit 4ba7b49cdd
33 changed files with 281 additions and 367 deletions
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89
aqhome/msg/msg_node.c
View File

@@ -16,10 +16,15 @@
#include <gwenhywfar/debug.h>
#define COM_USE_CRC8 1
#ifdef COM_USE_CRC8
static uint8_t _calcCrc8Checksum(const uint8_t *ptr, uint8_t len);
#else
static uint8_t _calcXorChecksum(const uint8_t *ptr, uint8_t len);
#endif
uint8_t AQH_NodeMsg_GetDestAddress(const GWEN_MSG *msg)
@@ -104,8 +109,13 @@ int AQH_NodeMsg_IsMsgComplete(const GWEN_MSG *msg)
int AQH_NodeMsg_IsChecksumValid(const GWEN_MSG *msg)
{
if (msg && AQH_NodeMsg_IsMsgComplete(msg))
if (msg && AQH_NodeMsg_IsMsgComplete(msg)) {
#ifdef COM_USE_CRC8
return (_calcCrc8Checksum(GWEN_Msg_GetConstBuffer(msg), GWEN_Msg_GetBytesInBuffer(msg))==0)?1:0;
#else
return (_calcXorChecksum(GWEN_Msg_GetConstBuffer(msg), GWEN_Msg_GetBytesInBuffer(msg))==0)?1:0;
#endif
}
return 0;
}
@@ -116,7 +126,11 @@ int AQH_NodeMsg_AddChecksum(GWEN_MSG *msg)
if (msg) {
int rv;
#ifdef COM_USE_CRC8
rv=GWEN_Msg_AddByte(msg, _calcCrc8Checksum(GWEN_Msg_GetConstBuffer(msg), GWEN_Msg_GetBytesInBuffer(msg)));
#else
rv=GWEN_Msg_AddByte(msg, _calcXorChecksum(GWEN_Msg_GetConstBuffer(msg), GWEN_Msg_GetBytesInBuffer(msg)));
#endif
if (rv<0) {
DBG_INFO(NULL, "here (%d)", rv);
return rv;
@@ -128,6 +142,45 @@ int AQH_NodeMsg_AddChecksum(GWEN_MSG *msg)
uint32_t AQH_NodeMsg_GetUint32At(const GWEN_MSG *msg, int offs, int defaultValue)
{
if ((GWEN_Msg_GetBytesInBuffer(msg)>=offs+4)) {
const uint8_t *ptr;
ptr=GWEN_Msg_GetConstBuffer(msg)+offs;
return (uint32_t)(ptr[0])+(ptr[1]<<8)+(ptr[2]<<16)+(ptr[3]<<24);
}
return defaultValue;
}
uint16_t AQH_NodeMsg_GetUint16At(const GWEN_MSG *msg, int offs, int defaultValue)
{
if ((GWEN_Msg_GetBytesInBuffer(msg)>=offs+2)) {
const uint8_t *ptr;
ptr=GWEN_Msg_GetConstBuffer(msg)+offs;
return (uint16_t)(ptr[0])+(ptr[1]<<8);
}
return defaultValue;
}
uint8_t AQH_NodeMsg_GetUint8At(const GWEN_MSG *msg, int offs, int defaultValue)
{
if ((GWEN_Msg_GetBytesInBuffer(msg)>=offs+1)) {
const uint8_t *ptr;
ptr=GWEN_Msg_GetConstBuffer(msg)+offs;
return ptr[0];
}
return defaultValue;
}
void AQH_NodeMsg_DumpToBuffer(const GWEN_MSG *msg, GWEN_BUFFER *dbuf, const char *sText)
{
GWEN_Buffer_AppendArgs(dbuf,
@@ -171,20 +224,7 @@ uint32_t AQH_NodeMsg_GetMsgGroup(uint8_t msgType)
uint8_t _calcXorChecksum(const uint8_t *ptr, uint8_t len)
{
int i;
uint8_t x=0;
for (i=0; i<len; i++, ptr++) {
x^=*ptr;
}
return x;
}
#ifdef COM_USE_CRC8
uint8_t _calcCrc8Checksum(const uint8_t *ptr, uint8_t len)
{
int i;
@@ -204,6 +244,21 @@ uint8_t _calcCrc8Checksum(const uint8_t *ptr, uint8_t len)
return x;
}
#else
uint8_t _calcXorChecksum(const uint8_t *ptr, uint8_t len)
{
int i;
uint8_t x=0;
for (i=0; i<len; i++, ptr++) {
x^=*ptr;
}
return x;
}
#endif