Change EezTire-E618 checksum, include flags (merbanan#2664)

Fix checksum, pressure calculations and add fast_leak reporting

src/devices/tpms_eezrv.c

@@ -14,28 +14,28 @@
 /**
 EezTire E618 TPMS.
 
-Eez RV supported model TPMS10ATC (E618) : https://eezrvproducts.com/shop/ols/products/tpms10atc
+Eez RV supported TPMS sensor model E618 : https://eezrvproducts.com/shop/ols/products/tpms-system-e518-anti-theft-replacement-sensor-1-ea
 
-S.a issue #2384
+S.a issue #2384, #2657
 
 Data layout:
 
-    PRE CC IIIIII PP TT FF 00
+    PRE CC IIIIII PP TT FF FF
 
 - PRE : FFFF
 - C : 8 bit CheckSum
 - I: 24 bit ID
 - P: 8 bit pressure  P * 2.5 = Pressure kPa
 - T: 8 bit temperature   T - 50 = Temperature C
-- F: 8 bit battery (not verified) and deflation pressure (for sure) flags
+- F: 16  bit battery (not verified), deflation pressure (for sure), pressure modifier flags
 
 Raw Data example :
 
     ffff 8b 0d177e 8f 4a 10 00
 
 Format string:
 
-    CHECKSUM:8h ID:24h KPA:8d TEMP:8d FLAG:4b 4h8h
+    CHECKSUM:8h ID:24h KPA:8d TEMP:8d FLAG:8b 8b
 
 Decode example:
 
@@ -55,38 +55,48 @@ static int tpms_eezrv_decode(r_device *decoder, bitbuffer_t *bitbuffer)
     bitbuffer_invert(bitbuffer);
     pos = bitbuffer_search(bitbuffer, 0, pos, preamble_pattern, sizeof(preamble_pattern) * 8);
     if (pos >= bitbuffer->bits_per_row[0]) {
-        decoder_log(decoder, 2, __func__, "Preamble not found");
+        decoder_log(decoder, 3, __func__, "Preamble not found");
         return DECODE_ABORT_EARLY;
     }
-    if (pos + 7 * 8 > bitbuffer->bits_per_row[0]) {
+    if (pos + 8 * 8 > bitbuffer->bits_per_row[0]) {
         decoder_log(decoder, 2, __func__, "Length check fail");
         return DECODE_ABORT_LENGTH;
     }
-    uint8_t b[6]  = {0};
+    uint8_t b[7]  = {0};
     uint8_t cc[1] = {0};
     bitbuffer_extract_bytes(bitbuffer, 0, pos + 16, cc, sizeof(cc) * 8);
     bitbuffer_extract_bytes(bitbuffer, 0, pos + 24, b, sizeof(b) * 8);
+
     // verify checksum
-    if ((add_bytes(b, 6) & 0xff) != cc[0]) {
+    int computed_checksum = add_bytes(b, sizeof(b));
+    if (computed_checksum > 0xff) 
+        computed_checksum |= 0x80;
+
+    if ((computed_checksum & 0xff) != cc[0]) {
         decoder_log(decoder, 2, __func__, "Checksum fail");
         return DECODE_FAIL_MIC;
     }
-    float pressure_kPa = b[3] * 2.5;
-    int temperature_C  = b[4] - 50;
-    int flags          = b[5];
-
     char id_str[7];
-    snprintf(id_str, sizeof(id_str), "%02x%02x%02x", b[0], b[1], b[2]);
-    char flags_str[3];
-    snprintf(flags_str, sizeof(flags_str), "%x", flags);
-
+    sprintf(id_str, "%02x%02x%02x", b[0], b[1], b[2]);
+    int temperature_C      = b[4] - 50;
+    int flags1             = b[5];
+    int flags2             = b[6];
+    int fast_leak_detected = (flags1 & 0x10);
+    int fast_leak_resolved = (flags1 & 0x20); 
+
+    int fast_leak = fast_leak_detected && !fast_leak_resolved;
+    float pressure_kPa = (((flags2 & 0x01) << 8) + b[3]) * 2.5;
+
+    char flags_str[5];
+    sprintf(flags_str, "%02x%02x", flags1, flags2);
     /* clang-format off */
     data_t *data = data_make(
                     "model",            "",             DATA_STRING, "EezTire-E618",
                     "type",             "",             DATA_STRING, "TPMS",
                     "id",               "",             DATA_STRING, id_str,
                     "pressure_kPa",     "Pressure",     DATA_FORMAT, "%.0f kPa", DATA_DOUBLE, (double)pressure_kPa,
                     "temperature_C",    "Temperature",  DATA_FORMAT, "%.1f C", DATA_DOUBLE, (double)temperature_C,
+                    "fast_leak",        "Fast Leak",    DATA_INT, fast_leak,
                     "flags",            "Flags",        DATA_STRING, flags_str,
                     "mic",              "Integrity",    DATA_STRING, "CHECKSUM",
                     NULL);
@@ -102,13 +112,14 @@ static char const *const output_fields[] = {
         "id",
         "temperature_C",
         "pressure_kPa",
+        "fast_leak",
         "flags",
         "mic",
         NULL,
 };
 
 r_device const tpms_eezrv = {
-        .name        = "EezTire E618 (TPMS10ATC)",
+        .name        = "EezTire E618",
         .modulation  = OOK_PULSE_MANCHESTER_ZEROBIT,
         .short_width = 50,
         .long_width  = 50,