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protocol: support 32 bit system IDs #15

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protocol: support 32 bit system IDs #15

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33 changes: 25 additions & 8 deletions libs/cpp/protocol/receive.h
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Original file line number Diff line number Diff line change
Expand Up @@ -24,13 +24,19 @@ class ReceiveProtocol
public:
struct Callbacks {
std::function<void(int num_events_lost)> error; ///< lost events
std::function<void(const mavlink_request_event_t&)> send_request_event_message;
/**
* Send a REQUEST_EVENT message. A target system id above 255 does not fit the 8 bit target_system field of the
* struct, which then reads as 0, so the target is passed alongside it. Pass it on to
* mavlink_msg_request_event_pack_chan(), which puts a wide target into the extended header, rather than
* encoding the struct as is.
*/
std::function<void(const mavlink_request_event_t&, uint32_t target_system_id)> send_request_event_message;
std::function<void(const mavlink_event_t&)> handle_event;
std::function<void(int timeout_ms)> timer_control; ///< control timer (single shot), timeout_ms <0 means to
///< disable the timer
};

ReceiveProtocol(const Callbacks& callbacks, uint8_t our_system_id, uint8_t our_component_id, uint8_t system_id,
ReceiveProtocol(const Callbacks& callbacks, uint32_t our_system_id, uint8_t our_component_id, uint32_t system_id,
uint8_t component_id)
: _callbacks(callbacks),
_our_system_id(our_system_id),
Expand Down Expand Up @@ -106,8 +112,12 @@ class ReceiveProtocol
}

// ignore events that are not for us
// Note that destination_system is 8 bit and, unlike a target_system field, is not a routing target, so it
// never moves into the extended header of a 32 bit system id setup. A system id above 255 therefore cannot be
// addressed by an event at all and only broadcast events (destination_system 0) reach us. Supporting that
// needs a wider field in the EVENT message itself.
if (event_msg.destination_system != _our_system_id && event_msg.destination_system != 0) {
LIBEVENTS_DEBUG_PRINTF("Ignoring event not for us (sys id: %i != %i)\n", event_msg.destination_system,
LIBEVENTS_DEBUG_PRINTF("Ignoring event not for us (sys id: %i != %u)\n", event_msg.destination_system,
_our_system_id);
return;
}
Expand Down Expand Up @@ -142,13 +152,15 @@ class ReceiveProtocol
void requestEvent(uint16_t sequence)
{
mavlink_request_event_t msg{};
msg.target_system = _system_id;
// A target above 255 does not fit the payload field and belongs into the extended header, which the caller
// packs. Leaving 0 here matches what the wire does for such an extended target.
msg.target_system = _system_id > 255 ? 0 : static_cast<uint8_t>(_system_id);
msg.target_component = _component_id;
msg.first_sequence = msg.last_sequence = sequence;

LIBEVENTS_DEBUG_PRINTF("requesting seq %i\n", sequence);

_callbacks.send_request_event_message(msg);
_callbacks.send_request_event_message(msg, _system_id);
// start a timer (or reset existing timer)
if (_callbacks.timer_control) {
_callbacks.timer_control(100);
Expand Down Expand Up @@ -181,7 +193,12 @@ class ReceiveProtocol
mavlink_response_event_error_t event_error;
mavlink_msg_response_event_error_decode(&message, &event_error);

if (event_error.target_system != _our_system_id || event_error.target_component != _our_component_id) {
// The decoded struct holds the raw 8 bit payload field, which reads as 0 when the target did not fit and
// travelled in the extended header instead. The getter takes that into account, so use it rather than
// event_error.target_system.
const uint32_t target_system = mavlink_msg_response_event_error_get_target_system(&message);

if (target_system != _our_system_id || event_error.target_component != _our_component_id) {
return;
}

Expand Down Expand Up @@ -222,10 +239,10 @@ class ReceiveProtocol
bool _has_current_sequence{false};
uint32_t _latest_current_sequence; ///< latest received sequence number via mavlink_current_event_sequence_t

uint8_t _our_system_id;
uint32_t _our_system_id;
uint8_t _our_component_id;

uint8_t _system_id;
uint32_t _system_id;
uint8_t _component_id;
};

Expand Down
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