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suunto_nautic: decode multi-gas mixes and link tanks to gas + volume #1

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Merged
latishab merged 1 commit into from
Sep 5, 2026
Merged

suunto_nautic: decode multi-gas mixes and link tanks to gas + volume #1

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55 changes: 46 additions & 9 deletions src/suunto_nautic_parser.c
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Original file line number Diff line number Diff line change
Expand Up @@ -121,12 +121,24 @@
// gives low > high.
#define SUMMARY_GF_LOW 0x35 // uint16 LE, %
#define SUMMARY_GF_HIGH 0x33 // uint16 LE, %
#define SUMMARY_GAS_BASE 0xC7 // first gas; 4 bytes each: id, O2%, He%, type
// Gas/cylinder records: an array starting at SUMMARY_GAS_BASE, one 45-byte
// record per configured gas. The record index equals the cylinder slot /
// GasNumber, so tank i uses gas i. Within a record: O2% at +1, He% at +2,
// PO2-max (float32 LE, bar) at +5, cylinder water capacity (float32 LE, m^3)
// at +9. Confirmed on two real dual-gas dives (Air 12 L + NX26 5.7 L, two
// transmitters -- issue #29/#33/#34); a lone gas dive stops at the first
// implausible slot, as before.
#define SUMMARY_GAS_BASE 0xC7
#define SUMMARY_GAS_STRIDE 45
#define SUMMARY_GAS_O2 1 // uint8, %
#define SUMMARY_GAS_HE 2 // uint8, %
#define SUMMARY_GAS_VOLUME 9 // float32 LE, m^3

typedef struct suunto_nautic_tank_t {
unsigned int used;
double beginpressure; // bar
double endpressure; // bar
unsigned int gasmix; // gas index (== cylinder slot / GasNumber)
} suunto_nautic_tank_t;

typedef struct suunto_nautic_parser_t {
Expand All @@ -149,6 +161,7 @@ typedef struct suunto_nautic_parser_t {
// From the /Summary SBEM section appended after the profile, if present.
unsigned int ngasmixes;
dc_gasmix_t gasmix[MAX_GASMIXES];
double gasvolume[MAX_GASMIXES]; // cylinder water capacity, litres (0 = unknown)
unsigned int have_decomodel;
dc_decomodel_t decomodel;
} suunto_nautic_parser_t;
Expand Down Expand Up @@ -298,17 +311,25 @@ suunto_nautic_parse_summary (suunto_nautic_parser_t *parser, const unsigned char
}

for (unsigned int i = 0; i < MAX_GASMIXES; i++) {
size_t base = SUMMARY_GAS_BASE + (size_t) i * 4;
if (base + 3 > size)
size_t base = SUMMARY_GAS_BASE + (size_t) i * SUMMARY_GAS_STRIDE;
if (base + SUMMARY_GAS_O2 >= size)
break;
unsigned int o2 = sbem[base + 1];
unsigned int he = sbem[base + 2];
unsigned int o2 = sbem[base + SUMMARY_GAS_O2];
unsigned int he = sbem[base + SUMMARY_GAS_HE];
if (o2 < 1 || o2 > 100 || he > 100 || o2 + he > 100)
break; // unused/implausible slot -- stop
parser->gasmix[parser->ngasmixes].oxygen = o2 / 100.0;
parser->gasmix[parser->ngasmixes].helium = he / 100.0;
parser->gasmix[parser->ngasmixes].nitrogen = 1.0 - (o2 + he) / 100.0;
parser->gasmix[parser->ngasmixes].usage = DC_USAGE_NONE;
unsigned int g = parser->ngasmixes;
parser->gasmix[g].oxygen = o2 / 100.0;
parser->gasmix[g].helium = he / 100.0;
parser->gasmix[g].nitrogen = 1.0 - (o2 + he) / 100.0;
parser->gasmix[g].usage = DC_USAGE_NONE;
// Per-gas cylinder water capacity (float32 m^3) -> litres, when the
// record's volume field is present and physically sane.
if (base + SUMMARY_GAS_VOLUME + 4 <= size) {
double vol_m3 = array_float_le (sbem + base + SUMMARY_GAS_VOLUME);
if (vol_m3 > 0.0 && vol_m3 < 1.0)
parser->gasvolume[g] = vol_m3 * 1000.0;
}
parser->ngasmixes++;
}
}
Expand Down Expand Up @@ -531,6 +552,9 @@ suunto_nautic_parser_parse (dc_parser_t *abstract, dc_sample_callback_t callback
continue;
tankmap[key] = (int) ntanks;
tank[ntanks].used = 1;
// Cylinder slot index == GasNumber, so this tank
// breathes gas i (linked to gasmix[i] below).
tank[ntanks].gasmix = i;
// Begin from the first observed reading (the deferred one for Pressure2).
tank[ntanks].beginpressure = (field == 1 && p2_first[i] >= 0)
? p2_first[i] / 100000.0 : bar;
Expand Down Expand Up @@ -771,6 +795,7 @@ suunto_nautic_parser_parse (dc_parser_t *abstract, dc_sample_callback_t callback
parser->ngasmixes = 0;
parser->have_decomodel = 0;
memset (parser->gasmix, 0, sizeof (parser->gasmix));
memset (parser->gasvolume, 0, sizeof (parser->gasvolume));
memset (&parser->decomodel, 0, sizeof (parser->decomodel));
if (profile_size < abstract->size) {
suunto_nautic_parse_summary (parser, abstract->data + profile_size,
Expand Down Expand Up @@ -855,6 +880,18 @@ suunto_nautic_parser_get_field (dc_parser_t *abstract, dc_field_type_t type, uns
tank->endpressure = parser->tank[flags].endpressure;
tank->gasmix = DC_GASMIX_UNKNOWN;
tank->usage = DC_USAGE_NONE;
// Link the tank to its gas (slot index) and expose the per-gas
// cylinder size from the /Summary when both are known.
{
unsigned int gi = parser->tank[flags].gasmix;
if (gi < parser->ngasmixes) {
tank->gasmix = gi;
if (parser->gasvolume[gi] > 0.0) {
tank->type = DC_TANKVOLUME_METRIC;
tank->volume = parser->gasvolume[gi];
}
}
}
break;
case DC_FIELD_LOCATION:
if (!parser->have_location)
Expand Down
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