From 925481ffd080a667c46e62faabbc3bd372edc3cc Mon Sep 17 00:00:00 2001
From: m7i-org <64315540+m7i-org@users.noreply.github.com>
Date: Fri, 11 Oct 2024 21:07:53 -0400
Subject: [PATCH] Sub-GHz: Nexus-TH weather station protocol improvements on
 detection (#256)

* feat(subghz): Nexus-TH improvements on detection

Added detection improvements for Nexus-TH as in https://github.com/merbanan/rtl_433/blob/00bd97c63a58083d2a79ccb7089786ff9d0fda2e/src/devices/nexus.c#L63-L78 :
 - If hum==0% there's no humidity sensor, so don't overwrite to 20%
 - If the Rubicson check matches, then it's probably not a Nexus-TH
 - Check temp range beween -50C and 100C

* Update changelog

---------

Co-authored-by: Willy-JL <49810075+Willy-JL@users.noreply.github.com>
---
 CHANGELOG.md                    |  1 +
 lib/subghz/protocols/nexus_th.c | 31 ++++++++++++++++++++++++++-----
 2 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a85a803de..960e17a5a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -70,6 +70,7 @@
     - Enforce int module (like in OFW) usage due to lack of required hardware on external boards (PathIsolate (+rf switch for multiple paths)) and incorrect usage and/or understanding the purpose of frequency analyzer app by users, it should be used only to get frequency of the remote placed around 1-10cm around flipper's left corner
     - Fix possible GSM mobile towers signal interference by limiting upper frequency to 920mhz max
     - Fix duplicated frequency lists and use user config for nearest frequency selector too
+  - Nexus-TH weather station protocol improvements on detection (#256 by @m7i-org)
 - Infrared:
   - Additions to MNTM specific LED, Digital Sign, Monitor universal remotes from IRDB (#240 by @jaylikesbunda)
   - UL: Replace LEDs universal remote with new one by Unleashed team, includes color options (by @amec0e & @xMasterX)
diff --git a/lib/subghz/protocols/nexus_th.c b/lib/subghz/protocols/nexus_th.c
index 0ed331967..6a0585af7 100644
--- a/lib/subghz/protocols/nexus_th.c
+++ b/lib/subghz/protocols/nexus_th.c
@@ -101,11 +101,30 @@ void ws_protocol_decoder_nexus_th_reset(void* context) {
 static bool ws_protocol_nexus_th_check(WSProtocolDecoderNexus_TH* instance) {
     uint8_t type = (instance->decoder.decode_data >> 8) & 0x0F;
 
-    if((type == NEXUS_TH_CONST_DATA) && ((instance->decoder.decode_data >> 4) != 0xffffffff)) {
-        return true;
-    } else {
-        return false;
-    }
+    if(type != NEXUS_TH_CONST_DATA) return false;
+    if((instance->decoder.decode_data >> 4) == 0xffffffff) return false;
+
+    if(!((instance->decoder.decode_data >> 23) & 1) &&
+       ((instance->decoder.decode_data >> 12) & 0x07FF) > 1000)
+        return false; // temp>100C
+    if(((instance->decoder.decode_data >> 23) & 1) &&
+       (~(instance->decoder.decode_data >> 12) & 0x07FF) > 500)
+        return false; // temp<-50C
+    if((instance->decoder.decode_data & 0xFF) > 100) return false; // hum>100
+
+    // The nexus protocol will trigger on rubicson data, so calculate the rubicson crc and make sure
+    // it doesn't match. By guesstimate it should generate a correct crc 1/255% of the times.
+    // So less then 0.5% which should be acceptable.
+    uint8_t msg_rubicson_crc[] = {
+        instance->decoder.decode_data >> 28,
+        instance->decoder.decode_data >> 20,
+        instance->decoder.decode_data >> 12,
+        0xf0,
+        (instance->decoder.decode_data & 0xf0) | (instance->decoder.decode_data & 0x0f)};
+
+    if(subghz_protocol_blocks_crc8(msg_rubicson_crc, 5, 0x31, 0x6c) == 0)
+        return false; // rubicson match, probably not a Nexus
+
     return true;
 }
 
@@ -214,6 +233,8 @@ static void ws_protocol_nexus_th_remote_controller(WSBlockGeneric* instance) {
     instance->humidity = instance->data & 0xFF;
     if(instance->humidity > 95)
         instance->humidity = 95;
+    else if(instance->humidity == 0)
+        instance->humidity = WS_NO_HUMIDITY;
     else if(instance->humidity < 20)
         instance->humidity = 20;
 }