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add calcMaxPacketMillis

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This commit is contained in:
taco
2026-07-17 21:15:09 +10:00
parent b55d69e57a
commit 975a673efd
2 changed files with 24 additions and 0 deletions
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src/helpers/radiolib/RadioLibWrappers.cpp
+18
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@@ -228,3 +228,21 @@ float RadioLibWrapper::packetScoreInt(float snr, int sf, int packet_len) {
return max(0.0, min(1.0, success_rate_based_on_snr * collision_penalty));
}
PacketMillis RadioLibWrapper::calcMaxPacketMillis(uint8_t sf, float bw, uint8_t cr, uint8_t preambleSymbols) {
// based on RadioLib's calculateTimeOnAir()
uint32_t tsym_us = ((uint32_t)10000 << sf) / (bw * 10);
uint32_t sfCoeff1_x4 = (sf == 5 || sf == 6) ? 25 : 17; // 6.25 : 4.25, semtech magic numbers to account for sync word + sfd
// preamble + syncword + sfd + header
uint32_t preamble_us = (((preambleSymbols + 8) * 4 + sfCoeff1_x4) * tsym_us) / 4;
// airtime for max packet at current radio settings
uint32_t total_us = _radio->getTimeOnAir(MAX_TRANS_UNIT);
// airtime for payload only (no preamble, header or SOF)
uint32_t payload_us = total_us > preamble_us ? total_us - preamble_us : 4000 - preamble_us; // fallback to 4 secs at worst case
// rescale payload_us for max possible CR
if (cr >= 5 && cr < 8) { payload_us = (payload_us * 8) / cr; }
return PacketMillis {(preamble_us + 999) / 1000, (payload_us + 999) / 1000};
}
src/helpers/radiolib/RadioLibWrappers.h
+6
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@@ -3,6 +3,11 @@
#include <Mesh.h>
#include <RadioLib.h>
struct PacketMillis {
uint32_t preambleMillis; // preamble-detect -> header-valid deadline
uint32_t payloadMillis; // header-valid -> rx-done deadline
};
class RadioLibWrapper : public mesh::Radio {
protected:
PhysicalLayer* _radio;
@@ -47,6 +52,7 @@ public:
virtual uint8_t getSpreadingFactor() const { return LORA_SF; }
static uint16_t preambleLengthForSF(uint8_t sf) { return sf <= 8 ? 32 : 16; }
void updatePreamble(uint8_t sf) { _preamble_sf = sf; _radio->setPreambleLength(preambleLengthForSF(sf)); }
PacketMillis calcMaxPacketMillis(uint8_t sf, float bw, uint8_t cr, uint8_t preambleSymbols);
virtual int16_t performChannelScan();
int getNoiseFloor() const override { return _noise_floor; }