added preamble conf placeholder with def val, changed def to 8 symbols

data/preferences.cfg

@@ -14,7 +14,7 @@
   "lora_rx_en": true,
   "lora_tx_en": true,
   "txPower": 23,
-  "preambleLen": 64,
+  "preambleLen": 8,
   "lora_cradapt": false,
   "lora_rssi2p": 34,
   "snraprsis": true,

data_embed/index.html

@@ -156,7 +156,7 @@ You like to enable, if you use your tracker portable and it should automatically
                     </div>
                     <div>
                         <label for="preambleLen">TX preamble length [symbols]</label>
-                        <input name="preambleLen" id="preambleLen" type="number" min="8" max="4096" title="A larger preamble size improves packet detection but increases transmission time. Range 8 to 4096 symbols.">
+                        <input name="preambleLen" id="preambleLen" type="number" min="8" max="4096" title="A larger preamble size improves packet detection but increases transmission time. Range 8 to 4096 symbols." placeholder="8">
                     </div>
                     <div>
                         <label for="lora_cradapt">Automatic CodeRate adaption on TX</label>

src/TTGO_T-Beam_LoRa_APRS.ino

@@ -448,8 +448,8 @@ boolean lora_tx_enabled = true;
   uint8_t txPower_cross_digi = 23;
 #endif
 #endif
-uint32_t preambleLen = 64; // default tx preamble len
-constexpr uint32_t rxTimeoutSymbols = 1024; // extended rx timout to avoid rejecting packets with long preamble
+uint16_t preambleLen = 8; // default tx preamble len
+constexpr uint16_t rxTimeoutSymbols = 1024; // extended rx timout to avoid rejecting packets with long preamble
 
 #define UNITS_SPEED_KMH 1
 #define UNITS_SPEED_MS  2