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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 4e1f08b567
commit 7eb462173c
33 changed files with 281 additions and 367 deletions
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5
avr/MESSAGES
View File

@@ -198,6 +198,7 @@ Offset Length Meaning
8 2 packets out
10 2 collisions
12 2 aborted
14 2 no buffer errors
@@ -215,5 +216,9 @@ Offset Length Meaning
8 2 packets in
10 2 crc errors
12 2 io errors
14 2 no buffer errors
16 2 handled packets
18 2 missed

10
avr/com.asm
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@@ -63,13 +63,15 @@ comDataBegin:
comStatsRecvErrs: .byte 2
comStatsRecvCrcErrs: .byte 2
comStatsCollisions: .byte 2
comStatsMissed: .byte 2
comStatsAborted: .byte 2
comStatsIgnored: .byte 2
comStatsHandled: .byte 2
comStatsCollisions: .byte 2
comStatsAborted: .byte 2
comStatsNoBuffer: .byte 2
comStatsSendNoBuffer: .byte 2
comStatsRecvNoBuffer: .byte 2
comRecvBuffersReadPos: .byte 1
comRecvBuffersWritePos: .byte 1
@@ -223,6 +225,8 @@ COM_AllocBufferAndGetXY:
sec
ret
COM_AllocBufferAndGetXY_error:
ldi xl, LOW(comStatsSendNoBuffer)
ldi xh, HIGH(comStatsSendNoBuffer)
clc
ret

24
avr/com_crc.asm
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@@ -1,4 +1,10 @@
#define COM_USE_CRC8 1
#define COM_CRC_POLYNOMIAL 0x97
; ***************************************************************************
; code
@@ -14,15 +20,20 @@
; - X : pointer to packet buffer
; OUT:
; - CFLAG: set if okay, clear otherwise
; MODIFIED REGS: R16, R17, R18, X
; MODIFIED REGS: R16, R17, R18, R19, X
comCalcAndAddChecksumByte:
adiw xh:xl, COM_MSG_OFFS_MSGLEN
ld r18, X ; read msg len
inc r18 ; account for dest address
inc r18 ; account for msg len bytes
inc r18 ; account for msg len byte
sbiw xh:xl, COM_MSG_OFFS_MSGLEN
#ifdef COM_USE_CRC8
ldi r19, COM_CRC_POLYNOMIAL
rcall cproCalcCrc8 ; (R16, R17, R18, R20, X)
#else
rcall cproCalcXor ; (R16, R17, R18, X)
#endif
st X, r16 ; add checksum byte
sec
ret
@@ -36,15 +47,20 @@ comCalcAndAddChecksumByte:
; - X : pointer to packet buffer
; OUT:
; - CFLAG: set if okay, clear otherwise
; MODIFIED REGS: R16, R17, R18, X
; MODIFIED REGS: R16, R17, R18, R19, R20, X
cproCheckMessageInBuffer:
adiw xh:xl, COM_MSG_OFFS_MSGLEN
ld r18, X ; read msg len
inc r18 ; account for dest address
inc r18 ; account for msg len bytes
inc r18 ; account for msg len byte
sbiw xh:xl, COM_MSG_OFFS_MSGLEN
#ifdef COM_USE_CRC8
ldi r19, COM_CRC_POLYNOMIAL
rcall cproCalcCrc8 ; (R16, R17, R18, R20, X)
#else
rcall cproCalcXor ; (R16, R17, R18, X)
#endif
ld r17, X
cp r16,r17 ; should be equal
brne cproCheckMessageInBuffer_error

8
avr/com_recv.asm
View File

@@ -21,8 +21,8 @@
comReceivePacketHandleBuffer:
rcall COM_BufferAlloc
brcs comReceivePacketHandleBuffer_haveBuffer
ldi xl, LOW(comStatsNoBuffer)
ldi xh, HIGH(comStatsNoBuffer)
ldi xl, LOW(comStatsRecvNoBuffer)
ldi xh, HIGH(comStatsRecvNoBuffer)
rjmp comReceivePacketHandleBuffer_errorWithCounter
comReceivePacketHandleBuffer_haveBuffer:
@@ -72,7 +72,7 @@ comReceivePacketHandleBuffer_notforme:
; OUT:
; - CFLAG: set if okay, clear otherwise
; - R16: error code if CFLAG cleared
; MODIFIED REGISTERS: r16, r17, r18, X (r20, r21, r22)
; MODIFIED REGISTERS: r16, r17, r18, X (r19, r20, r21, r22)
comReceivePacketToXandCheck:
push xh
@@ -81,7 +81,7 @@ comReceivePacketToXandCheck:
pop xl
pop xh
brcc comReceivePacketToXandCheck_error
rcall cproCheckMessageInBuffer ; (R16, R17, R18, X)
rcall cproCheckMessageInBuffer ; (R16, R17, R18, R19, R20, X)
ldi r16, COM_ERR_CHECKSUM
brcc comReceivePacketToXandCheck_error
sec

18
avr/comproto.asm
View File

@@ -31,12 +31,12 @@
.equ CPRO_PAYLOAD_FLAGS_SECONDS = 0x01
.equ CPRO_PAYLOAD_FLAGS_UID = 0x02
.equ CPRO_PAYLOAD_FLAGS_RESERVED1 = 0x04
.equ CPRO_PAYLOAD_FLAGS_RESERVED2 = 0x08
.equ CPRO_PAYLOAD_FLAGS_RESERVED3 = 0x10
.equ CPRO_PAYLOAD_FLAGS_NUM0 = 0x20
.equ CPRO_PAYLOAD_FLAGS_NUM1 = 0x40
.equ CPRO_PAYLOAD_FLAGS_NUM3 = 0x80
.equ CPRO_PAYLOAD_FLAGS_SHIFT_NUM = 5
.equ CPRO_PAYLOAD_FLAGS_NUM0 = 0x08
.equ CPRO_PAYLOAD_FLAGS_NUM1 = 0x10
.equ CPRO_PAYLOAD_FLAGS_NUM2 = 0x20
.equ CPRO_PAYLOAD_FLAGS_NUM3 = 0x40
.equ CPRO_PAYLOAD_FLAGS_NUM4 = 0x80
.equ CPRO_PAYLOAD_FLAGS_SHIFT_NUM = 3
.equ CPRO_PACKET_HAVEADDR_OFFS_ADDRESS = COM_MSG_OFFS_PAYLOAD+4
@@ -244,7 +244,7 @@ cproEnqueueMsgWithCmdAndSrcAddr:
pop r20
pop xl
pop xh
rcall comCalcAndAddChecksumByte
rcall comCalcAndAddChecksumByte ; (R16, R17, R18, R19, X)
; mark buffer as enqueued with PRIO given in R20
rcall COM_EnqueuePacket ; (R15, R16)
@@ -331,9 +331,7 @@ cproCalcPayloadSize_l1:
brcc cproCalcPayloadSize_l2
add r4, r17 ; add 4 bytes
cproCalcPayloadSize_l2:
lsr r16
lsr r16
lsr r16 ; after this R16 contains CPRO_PAYLOAD_FLAGS_NUM0-3
lsr r16 ; shift out reserved1, after this R16 contains CPRO_PAYLOAD_FLAGS_NUM0-4
add r16, r4 ; add previous bytes to R16
ret

2
avr/comproto_addr.asm
View File

@@ -514,7 +514,7 @@ cproEnqueueAddressPacket:
st X+, r6 ; 5: value id
pop xl
pop xh
rcall comCalcAndAddChecksumByte
rcall comCalcAndAddChecksumByte ; (R16, R17, R18, R19, X)
; mark buffer as enqueued with PRIO "important" (higher retry count)
ldi r20, COM_BUFFER_PRIO_IMPORTANT

2
avr/comproto_device.asm
View File

@@ -40,7 +40,7 @@ CPRO_EnqueueDevice:
st X+, r17 ; 11: modules mask low
pop xl
pop xh
rcall comCalcAndAddChecksumByte
rcall comCalcAndAddChecksumByte ; (R16, R17, R18, R19, X)
; mark buffer as enqueued with PRIO "normal" (slightly limited number of retries)
ldi r20, COM_BUFFER_PRIO_NORMAL

36
avr/comproto_stats.asm
View File

@@ -23,26 +23,30 @@ CPRO_EnqueueComSendStats:
pop r16
brcc CPRO_EnqueueComSendStats_error
ldi r17, CPRO_PAYLOAD_FLAGS_UID | (6<<CPRO_PAYLOAD_FLAGS_SHIFT_NUM) ; seconds + 6 bytes payload
ldi r17, CPRO_PAYLOAD_FLAGS_UID | (8<<CPRO_PAYLOAD_FLAGS_SHIFT_NUM) ; seconds + 8 bytes payload
ldi r18, CPRO_CMD_COMSENDSTATS
push xh
push xl
rcall cproBeginMsgWithVariablePayload ; (R3, R4, R16, R17, R18, R19, R20, R21, X)
lds r16, comStatsPacketsOut ; 6: packets out
lds r16, comStatsPacketsOut ; packets out
st X+, r16
lds r16, comStatsPacketsOut+1
st X+, r16
lds r16, comStatsCollisions ; 8: collisions
lds r16, comStatsCollisions ; collisions
st X+, r16
lds r16, comStatsCollisions+1
st X+, r16
lds r16, comStatsAborted ; 10: aborted
lds r16, comStatsAborted ; aborted
st X+, r16
lds r16, comStatsAborted+1
st X+, r16
lds r16, comStatsSendNoBuffer ; sendNoBuffer
st X+, r16
lds r16, comStatsSendNoBuffer+1
st X+, r16
pop xl
pop xh
rcall comCalcAndAddChecksumByte
rcall comCalcAndAddChecksumByte ; (R16, R17, R18, R19, X)
; mark buffer as enqueued with PRIO "important" (higher retry count)
ldi r20, COM_BUFFER_PRIO_IMPORTANT
@@ -78,26 +82,38 @@ CPRO_EnqueueComRecvStats:
pop r16
brcc CPRO_EnqueueComRecvStats_error
ldi r17, CPRO_PAYLOAD_FLAGS_UID | (6<<CPRO_PAYLOAD_FLAGS_SHIFT_NUM) ; seconds + 6 bytes payload
ldi r17, CPRO_PAYLOAD_FLAGS_UID | (12<<CPRO_PAYLOAD_FLAGS_SHIFT_NUM) ; seconds + 6 bytes payload
ldi r18, CPRO_CMD_COMRECVSTATS
push xh
push xl
rcall cproBeginMsgWithVariablePayload ; (R3, R4, R16, R17, R18, R19, R20, R21, X)
lds r16, comStatsPacketsIn ; 6: packets in
lds r16, comStatsPacketsIn ; packets in
st X+, r16
lds r16, comStatsPacketsIn+1
st X+, r16
lds r16, comStatsRecvCrcErrs ; 8: CRC errors
lds r16, comStatsRecvCrcErrs ; CRC errors
st X+, r16
lds r16, comStatsRecvCrcErrs+1
st X+, r16
lds r16, comStatsRecvErrs ; 10: IO errors
lds r16, comStatsRecvErrs ; IO errors
st X+, r16
lds r16, comStatsRecvErrs+1
st X+, r16
lds r16, comStatsRecvNoBuffer ; no buffer
st X+, r16
lds r16, comStatsRecvNoBuffer+1
st X+, r16
lds r16, comStatsHandled ; handled
st X+, r16
lds r16, comStatsHandled+1
st X+, r16
lds r16, comStatsMissed ; missed
st X+, r16
lds r16, comStatsMissed+1
st X+, r16
pop xl
pop xh
rcall comCalcAndAddChecksumByte
rcall comCalcAndAddChecksumByte ; (R16, R17, R18, R19, X)
; mark buffer as enqueued with PRIO "important" (higher retry count)
ldi r20, COM_BUFFER_PRIO_IMPORTANT

2
avr/comproto_values.asm
View File

@@ -44,7 +44,7 @@ CPRO_EnqueueValue:
st X+, r11 ; 11: high denom
pop xl
pop xh
rcall comCalcAndAddChecksumByte
rcall comCalcAndAddChecksumByte ; (R16, R17, R18, R19, X)
; mark buffer as enqueued with PRIO "normal" (slightly limited number of retries)
ldi r20, COM_BUFFER_PRIO_NORMAL