Arexx IP-HA90

[MacH-21]

Hi All,
I am attempting to decode a couple of sensors,

https://www.conrad.com/p/arexx-ip-ha90-data-logger-sensor-unit-of-measurement-temperature-40-up-to-125-c-1313632
https://www.conrad.com/p/arexx-ip-th78ext-data-logger-sensor-unit-of-measurement-temperature-humidity-40-up-to-100-c-20-up-to-100-rh-1313634

I have caught and decoded most of the ip-ha90 temperature sensor this is a microchip rfpic12f675f 433.92M and a microchip mcp9808 temperature sensor.

rtl_433 -R 0 -X "n=name,m=FSK_MC_ZEROBIT,s=210,l=210,r=2500"

---

time : 2023-02-17 13:33:00
model : name count : 1 num_rows : 1 rows :
len : 122 data : 2aaaaaaad57c38ff7f6ffbbbadd27f8
codes : {122}2aaaaaaad57c38ff7f6ffbbbadd27f8
*** Saving signal to file g002_433.92M_250k.cu8 (45807 samples, 131072 bytes)

---

time : 2023-02-17 13:33:52
model : name count : 1 num_rows : 1 rows :
len : 121 data : 2aaaaaaad57c38ff7f6ffb93c03fff8
codes : {121}2aaaaaaad57c38ff7f6ffb93c03fff8
*** Saving signal to file g003_433.92M_250k.cu8 (45784 samples, 131072 bytes)

---

time : 2023-02-17 13:34:43
model : name count : 1 num_rows : 1 rows :
len : 121 data : 2aaaaaaad57c38ff7f6ffb73c738ff8
codes : {121}2aaaaaaad57c38ff7f6ffb73c738ff8
*** Saving signal to file g004_433.92M_250k.cu8 (45799 samples, 131072 bytes)

I have attached a zipfile with my info - captures and bitbench links at various stages,

I believe the last two bytes to be CRC of sorts but unable to confirm any advice/help would be appreciated.
ID_65934-Decode.txt
cu8-captures.zip

[zuckschwerdt]

With the ID you already found polarity and alignment, that's the hard part ;) The second to last byte is a CRC-8 (poly 0x31, init 0) on reflected bytes (MSB-LSB swap). Not sure what the last byte is, seems XOR based.

[MacH-21]

Wow, thanks for quick response I have been fixed on a 16 bit crc
07 8E 01 01 20 F6 48 2B D4 so.. 2B is the 8 bit crc ... D4 is the invert of the crc :)
what bytes do the crc cover is it 0x8E thru to 0x48

[zuckschwerdt]

the preceeding 7 bytes are covered by the crc
crc8(&b[0], 8, 0x31, 0x00) == 0; and crc8(&b[0], 7, 0x31, 0x00) == b[7];

[MacH-21]

Thanks

[zuckschwerdt]

There is now a decoder in #2487 -- let's discuss and finish this there.