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[BACKPORT 1.16] mavlink: add message spacing for AVAILABLE_MODES, for low bandwidth #25662

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Merged
dakejahl merged 1 commit into from
Oct 1, 2025
Merged

[BACKPORT 1.16] mavlink: add message spacing for AVAILABLE_MODES, for low bandwidth #25662

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19 changes: 17 additions & 2 deletions src/modules/mavlink/streams/AVAILABLE_MODES.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -58,6 +58,10 @@ class MavlinkStreamAvailableModes : public MavlinkStream
}

private:
/* Max 2.5 seconds delay for all possible modes to avoid ACK timeout in ground station */
static constexpr uint32_t MAX_DELAY_US = 2500000 / vehicle_status_s::NAVIGATION_STATE_MAX;
/* Only delay if the transmit of one mode takes at least 1ms, this avoids a lot of fast delay calls */
static constexpr uint32_t MIN_DELAY_THRESHOLD = 1000;
static constexpr int MAX_NUM_EXTERNAL_MODES = vehicle_status_s::NAVIGATION_STATE_EXTERNAL8 -
vehicle_status_s::NAVIGATION_STATE_EXTERNAL1 + 1;

Expand All @@ -76,8 +80,13 @@ class MavlinkStreamAvailableModes : public MavlinkStream
uint32_t _last_valid_nav_states_mask{0};
uint32_t _last_can_set_nav_states_mask{0};

void send_single_mode(const vehicle_status_s &vehicle_status, int mode_index, int total_num_modes, uint8_t nav_state)
void send_single_mode(const vehicle_status_s &vehicle_status, int mode_index, int total_num_modes, uint8_t nav_state,
uint32_t delay_us = 0)
{
if (delay_us > 0) {
px4_usleep(delay_us);
}

mavlink_available_modes_t available_modes{};
available_modes.mode_index = mode_index;
available_modes.number_modes = total_num_modes;
Expand Down Expand Up @@ -139,12 +148,18 @@ class MavlinkStreamAvailableModes : public MavlinkStream

int total_num_modes = math::countSetBits(vehicle_status.valid_nav_states_mask);

float mode_transmit_time = (float)(MAVLINK_MSG_ID_AVAILABLE_MODES_LEN + MAVLINK_NUM_NON_PAYLOAD_BYTES) /
_mavlink->get_data_rate();
uint32_t delay_us = (uint32_t)(mode_transmit_time * 1e6f);
delay_us = delay_us >= MIN_DELAY_THRESHOLD ? delay_us : 0;
delay_us = delay_us > MAX_DELAY_US ? MAX_DELAY_US : delay_us;

if (mode_index == 0) { // All
int cur_mode_index = 1;

for (uint8_t nav_state = 0; nav_state < vehicle_status_s::NAVIGATION_STATE_MAX; ++nav_state) {
if ((1u << nav_state) & vehicle_status.valid_nav_states_mask) {
send_single_mode(vehicle_status, cur_mode_index, total_num_modes, nav_state);
send_single_mode(vehicle_status, cur_mode_index, total_num_modes, nav_state, delay_us);
++cur_mode_index;
}
}
Expand Down
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