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EXBUS non documented packet type with a valid CRC received periodically

  • borisff
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EXBUS non documented packet type with a valid CRC received periodically

20 Juli 2026 22:25
#
DC24v1 v5.08 REX3, latest FW v1.15.

Using a PowerBox PBS-TAV ExBus sensor and analyse/decode
the serial link with an ESP32 and SAMD21, the master (the REX3) from time to
time sends a NON DOCUMENTED frame in EX_Bus_protokol_v121_EN.pdf
that has a valid CRC.

Packet type not documented received from master, with a valid crc: 0x3D 0x01 0x08 Packet_ID 0x40 0x00 Crc16-byte1 Crc16-byte2
A documented telemetry request is                                                    0x3D 0x01 0x08 Packet_ID 0x3A 0x00 Crc16-byte1 Crc16-byte2

The only difference is the the data identifier 0x40 (64) instead of 0x3A. (0x3A The data identifier – request for telemetry, documented).

It's the same behavior with a DIY EXBus sensor as with the PowerBox PBS-TAV. It's same behavior using an ESP32 or a SAMD21 as 'sniffer'.

May be it's 'noise' on the link, but the constant repetition, the always correct CRC for all decoded packets including these unknow packets negates 'noise'.

Currently, as not documented, DIY EXBus libraries found available on the net do nothing with theses packets, or more probably, aren't even aware that they are some.

PS: I'm not expecting anything with this post, but I'm by nature curious.

Below, "unk:726" is a counter that counts these unknow valid crc packets.
The frequency is low. Aprox. 450 in Aprox. 10 minutes.

21:22:05.195 -> 38462<SN>BC50A411<PBS-TAV>Id<5>Typ<1>Dat<14b>Lab<Trip><0.00><km>
21:22:05.195 -> 38462<SN>BC50A411<PBS-TAV>Id<1>Typ<1>Dat<14b>Lab<Speed><0.00><km/h>
21:22:05.276 -> 38465<SN>BC50A411<PBS-TAV>Id<1>Typ<1>Dat<14b>Lab<Speed><0.00><km/h>
21:22:05.276 -> unk:726
21:22:05.276 -> unk:727
21:22:05.276 -> 38465<SN>BC50A411<PBS-TAV>Id<2>Typ<1>Dat<14b>Lab<Altitude><0.00><m>
21:22:05.316 -> 38467<SN>BC50A411<PBS-TAV>Id<3>Typ<1>Dat<14b>Lab<Climbrate><0.00><m/s>
21:22:05.351 -> 38467<SN>BC50A411<PBS-TAV>Id<4>Typ<1>Dat<14b>Lab<Climb. TEC><0.00><m/s>
21:22:05.351 -> unk:728
21:22:05.397 -> 38468<SN>BC50A411<PBS-TAV>Id<5>Typ<1>Dat<14b>Lab<Trip><0.00><km>
21:22:05.397 -> 38468<SN>BC50A411<PBS-TAV>Id<1>Typ<1>Dat<14b>Lab<Speed><0.00><km/h>
21:22:05.430 -> 38471<SN>BC50A411<PBS-TAV>Id<1>Typ<1>Dat<14b>Lab<Speed><0.00><km/h>
21:22:05.475 -> 38471<SN>BC50A411<PBS-TAV>Id<2>Typ<1>Dat<14b>Lab<Altitude><0.00><m>
...
21:22:09.167 -> 38591<SN>BC50A411<PBS-TAV>Id<1>Typ<1>Dat<14b>Lab<Speed><0.00><km/h>
21:22:09.167 -> 38591<SN>BC50A411<PBS-TAV>Id<2>Typ<1>Dat<14b>Lab<Altitude><0.00><m>
21:22:09.233 -> 38593<SN>BC50A411<PBS-TAV>Id<3>Typ<1>Dat<14b>Lab<Climbrate><0.00><m/s>
21:22:09.233 -> 38593<SN>BC50A411<PBS-TAV>Id<4>Typ<1>Dat<14b>Lab<Climb. TEC><0.00><m/s>
21:22:09.264 -> 38594<SN>BC50A411<PBS-TAV>Id<5>Typ<1>Dat<14b>Lab<Trip><0.00><km>
21:22:09.264 -> unk:729
21:22:09.264 -> unk:730
21:22:09.308 -> 38594<SN>BC50A411<PBS-TAV>Id<1>Typ<1>Dat<14b>Lab<Speed><0.00><km/h>
21:22:09.341 -> 38597<SN>BC50A411<PBS-TAV>Id<1>Typ<1>Dat<14b>Lab<Speed><0.00><km/h>
21:22:09.385 -> unk:731
21:22:09.385 -> 38597<SN>BC50A411<PBS-TAV>Id<2>Typ<1>Dat<14b>Lab<Altitude><0.00><m>
21:22:09.418 -> 38599<SN>BC50A411<PBS-TAV>Id<3>Typ<1>Dat<14b>Lab<Climbrate><0.00><m/s>
21:22:09.418 -> 38599<SN>BC50A411<PBS-TAV>Id<4>Typ<1>Dat<14b>Lab<Climb. TEC><0.00><m/s>
21:22:09.463 -> 38600<SN>BC50A411<PBS-TAV>Id<5>Typ<1>Dat<14b>Lab<Trip><0.00><km>
21:22:09.509 -> 38600<SN>BC50A411<PBS-TAV>Id<1>Typ<1>Dat<14b>Lab<Speed><0.00><km/h>


 

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  • borisff
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Re: EXBUS non documented packet type with a valid CRC received periodically

21 Juli 2026 07:43
#
Arduino sketch for XIAO SAMD21 or ESP32 and PowerBox PBS-TAV

setup
741:cnt:1:0:0x3D 1:0x1 2:0x8 3:0x86 4:0x40 5:0x0 6:0xC0 7:0x80 
9:cnt:2:0:0x3D 1:0x1 2:0x8 3:0x86 4:0x40 5:0x0 6:0xC0 7:0x80 
89:cnt:3:0:0x3D 1:0x1 2:0x8 3:0x86 4:0x40 5:0x0 6:0xC0 7:0x80 
3900:cnt:4:0:0x3D 1:0x1 2:0x8 3:0x8A 4:0x40 5:0x0 6:0x63 7:0x25 
9:cnt:5:0:0x3D 1:0x1 2:0x8 3:0x8A 4:0x40 5:0x0 6:0x63 7:0x25 
89:cnt:6:0:0x3D 1:0x1 2:0x8 3:0x8A 4:0x40 5:0x0 6:0x63 7:0x25 
3900:cnt:7:0:0x3D 1:0x1 2:0x8 3:0x8E 4:0x40 5:0x0 6:0x2 7:0x46 
9:cnt:8:0:0x3D 1:0x1 2:0x8 3:0x8E 4:0x40 5:0x0 6:0x2 7:0x46 
89:cnt:9:0:0x3D 1:0x1 2:0x8 3:0x8E 4:0x40 5:0x0 6:0x2 7:0x46 
3900:cnt:10:0:0x3D 1:0x1 2:0x8 3:0x92 4:0x40 5:0x0 6:0x34 7:0x66 
9:cnt:11:0:0x3D 1:0x1 2:0x8 3:0x92 4:0x40 5:0x0 6:0x34 7:0x66 

 

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