Ashin Walpola
21e01499d8
The bench transmitter sent a parked car: one fixed position, speed 0, no heading, a CAM every second. It now simulates a car driving a loop through six waypoints around Berliner Tor on the real streets, which makes it a moving target for the app's map and the use case detection without taking a car out. The route is generated, not hand-traced. tools/make_route.py asks the OSRM demo server for a driving route through the waypoints and back to the first, thins the 371 street points to 103 (none more than 1.5 m off the line), and writes main/route_points.h. It also saves OSRM's answer (--offline rebuilds from it) and a map page to check the route before flashing. Each waypoint is sent with the direction towards the next one: without it, points on divided roads such as Beim Strohhause snapped to the opposite carriageway and the loop came out at 8.4 km of U-turns. With it the loop is 5.2 km, still including two turn-round detours that OSRM needs to reach the waypoints legally (Borgfelder Strasse / Anckelmannsplatz, and Nagelsweg / Norderstrasse / Repsoldstrasse). Route data (c) OpenStreetMap contributors, ODbL. main/route.c moves the car along the points. It cruises at 50 km/h and limits each bend to the speed that keeps sideways acceleration at 2 m/s^2, so a junction turn is taken at about 15 km/h and a gentle curve barely slows it; braking (2 m/s^2) and acceleration (1.5 m/s^2) are planned across as many points as a bend needs. A simulated lap on the host is 5.16 km in 7.7 min, averaging 40 km/h. CAMs now follow the EN 302 637-2 generation rules instead of a fixed 1 Hz: checked every 100 ms, sent on a heading change over 4 degrees, a move over 4 m, a speed change over 0.5 m/s, or after 1 s - about 3 Hz at 50 km/h. generationDeltaTime is milliseconds since boot. The GeoNetworking source position vector now carries the same speed and heading as the CAM instead of zeros. NOTES.md gains build and flash steps (including reading a board's app descriptor first, since both firmwares name their image obu_firmware.bin) and a section on the simulated drive. The pointer to docs/04-transmit-setup.md is corrected: that file is not in the repo. Flashed to the COM8 board and checked on its console: it starts driving on power-up and sends CAMs with changing position, speed and heading. Not yet received over the air.
50 lines
2.5 KiB
C
50 lines
2.5 KiB
C
#ifndef GEONET_H
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#define GEONET_H
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#include <stdint.h>
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#include <stddef.h>
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// Wraps an ITS application payload (e.g. from denm_encode) with a minimal
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// GeoNetworking Basic Header + Common Header + Single-Hop-Broadcast
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// extended header (HeaderType=TSB(5), HeaderSubtype=SINGLE_HOP(0), per
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// ETSI EN 302 636-4-1 table 9), then prepends a BTP-B header addressed to
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// the DENM service port (2002).
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//
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// `mac` is the 6-byte pseudonym/link-layer address - pass the SAME address
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// you hand to dot11p_build_frame's src address, since GN_ADDR's MID field
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// (the last 6 bytes of the 8-byte GN_ADDR) is defined to BE that
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// link-layer address (EN 302 636-4-1 clause 9.5.1). `station_type` is the
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// 5-bit ITS-S type from the same clause (5 = passengerCar) and gets packed
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// into GN_ADDR alongside the address.
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//
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// `latitude_tenmicrodeg`/`longitude_tenmicrodeg` go into the Source Long
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// Position Vector (clause 9.5.2) as plain 32-bit signed big-endian fields -
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// NOT UPER bit-packed like the DENM payload's position fields, this is a
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// fixed-width binary protocol. Pass the SAME values you gave denm_encode's
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// eventPosition, so the GN-layer position and the DENM's own claimed
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// position agree.
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//
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// Deliberate simplification: real DENM dissemination normally uses
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// GeoBroadcast (GBC, HeaderType=4) so RSUs/OBUs can forward it across an
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// area - that needs a sequence number + geo-area fields this skeleton
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// doesn't build yet. Single-hop broadcast is simpler and is the
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// best-tested decode path in the receiver firmware you already have
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// working (same extended header shape as CAM). Fine for a single-vehicle
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// beacon; revisit if you need real multi-hop forwarding later.
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//
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// `speed_cm_s` (0.01 m/s) and `heading_ddeg` (0.1 deg) also go into the Source Long Position
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// Vector; pass the same values as the CAM's high-frequency container. Speed is a 15-bit field, so
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// values above 32767 are clamped.
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//
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// `btp_dest_port` is the BTP-B destination port for the service being carried
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// (ETSI TS 103 248): 2001 = CAM, 2002 = DENM, 2003 = MAPEM, 2004 = SPATEM, ...
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//
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// Returns bytes written, or -1 if out buffer too small.
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int geonet_wrap_shb(const uint8_t *its_payload, int its_len,
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const uint8_t mac[6], uint8_t station_type,
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int32_t latitude_tenmicrodeg, int32_t longitude_tenmicrodeg,
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uint16_t speed_cm_s, uint16_t heading_ddeg,
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uint16_t btp_dest_port,
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uint8_t *out, size_t out_len);
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#endif
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