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Dynamic Power LQ and sensitivity
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Make dynamic power respond to reduced LQ as well as RSSI. LQ below a 'panic'
threshold raises the power directly to the configured maximum. LQ below a
more moderate threshold increments power by 1 dB.
Loss of telemetry is now handled directly using a "number of consecutive
missed telemetry packets" counter instead of waiting for the normal rx
disconnected timeout.
RSSI thresholds are now calculated relative to the rx sensitivity of the
current packet rate.
TX power can be sent in the sync packets for logging via BF black box and
display on the OSD (requires modified RX and BF firmwares).
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@JBKingdon
James authored and JBKingdon committed Jul 16, 2021
1 parent 630e3c6 commit 2f9be25
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Showing 2 changed files with 127 additions and 36 deletions.
18 changes: 9 additions & 9 deletions src/common.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -70,9 +70,9 @@ expresslrs_mod_settings_s ExpressLRS_AirRateConfig[RATE_MAX] = {

// Getting rxfail on indoor test quad, even though this is quicker than CR_4_5
// {1, RATE_500HZ, SX1280_LORA_BW_0800, SX1280_LORA_SF5, SX1280_LORA_CR_LI_4_6, 2000, TLM_RATIO_1_128, 8, 12},
{3, RATE_250HZ, SX1280_LORA_BW_0800, SX1280_LORA_SF6, SX1280_LORA_CR_LI_4_7, 4000, TLM_RATIO_1_64, 8, 12},
{4, RATE_150HZ, SX1280_LORA_BW_0800, SX1280_LORA_SF7, SX1280_LORA_CR_LI_4_7, 7692, TLM_RATIO_1_32, 4, 12}, // 130Hz
{5, RATE_50HZ, SX1280_LORA_BW_0800, SX1280_LORA_SF8, SX1280_LORA_CR_LI_4_7,13333, TLM_RATIO_1_32, 2, 12}}; // 75Hz
{3, RATE_250HZ, SX1280_LORA_BW_0800, SX1280_LORA_SF6, SX1280_LORA_CR_LI_4_7, 4000, TLM_RATIO_1_64, 8, 12},
{4, RATE_150HZ, SX1280_LORA_BW_0800, SX1280_LORA_SF7, SX1280_LORA_CR_LI_4_7, 7692, TLM_RATIO_1_32, 4, 12}, // 130Hz
{5, RATE_50HZ, SX1280_LORA_BW_0800, SX1280_LORA_SF8, SX1280_LORA_CR_LI_4_7, 13333, TLM_RATIO_1_32, 2, 12}}; // 75Hz

expresslrs_rf_pref_params_s ExpressLRS_AirRateRFperf[RATE_MAX] = {

Expand All @@ -85,12 +85,12 @@ expresslrs_rf_pref_params_s ExpressLRS_AirRateRFperf[RATE_MAX] = {

// long rx cycle times
// TODO check the TOA values
{0, RATE_1KHZ, -99, 675, 500, 1000, 100, 5000}, // no hw crc
{1, RATE_800HZ, -99, 871, 500, 1000, 100, 5000},
{2, RATE_500HZ, -105, 1626, 500, 1000, 100, 5000},
{3, RATE_250HZ, -108, 3567, 1000, 1000, 100, 5000},
{4, RATE_150HZ, -112, 6660, 1000, 4000, 100, 5000}, // todo, see if the large RFmodeCycleAddtionalTime can be reduced
{5, RATE_50HZ, -120,12059, 1000, 6000, 133, 5000}};
{0, RATE_1KHZ, -99, 675, 500, 1000, 100, 1000},
{1, RATE_800HZ, -99, 871, 500, 1000, 100, 1000},
{2, RATE_500HZ, -105, 1626, 500, 1000, 100, 1000},
{3, RATE_250HZ, -108, 3567, 1000, 1000, 100, 2000},
{4, RATE_150HZ, -112, 6660, 1000, 4000, 100, 2000}, // todo, see if the large RFmodeCycleAddtionalTime can be reduced
{5, RATE_50HZ, -120,12059, 1000, 6000, 133, 4000}};

#endif // ELRS_OG_COMPATIBILITY

Expand Down
145 changes: 118 additions & 27 deletions src/main.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -27,11 +27,34 @@
// Uncomment to enable some debug output on the LCD
// #define DEBUG_STATUS

// The threshold at which the TX power will be increased
#define DYN_POWER_MIN_RSSI -85
// The RSSI dB delta relative to the rx sensitivity at which the TX power will be increased
// So if the RXsensitivity is -105 and DYN_POWER_INCREASE_MARGIN is 15, power will be increase
// if rssi is below -90
#define DYN_POWER_INCREASE_MARGIN 15

// The threshold at which the TX power will be decreased
#define DYN_POWER_MAX_RSSI -70
// The RSSI dB delta above DYN_POWER_INCREASE_MARGIN at which the TX power will be decreased
// If RXsensitivity is -105, DYN_POWER_INCREASE_MARGIN is 15 and DYN_POWER_DECREASE_MARGIN is 10
// then power will be decreased when rssi is above -80 (105-15 = -90, then 10 above that is -80)
#define DYN_POWER_DECREASE_MARGIN 10

// The LQ below which the power will be increased to improve the link. The same value is used
// to prevent power being decreased even if the rssi is strong.
#define DYN_POWER_LQ_THRESHOLD 90

// The LQ below which the power will be increased directly to the configured max value
#define DYN_POWER_LQ_PANIC_THRESHOLD 50

// The number of consecutive missed telemetry packets to trigger full tx power
#define DYN_POWER_MISSED_TELEM_PACKET_THRESHOLD 4

#define DYN_POWER_RSSI_FILTER_CUTOFF_HZ 0.1f

#ifndef ELRS_OG_COMPATIBILITY

// This needs modified RX code to work
#define SEND_TX_POWER_IN_SYNC

#endif

extern "C" {

Expand Down Expand Up @@ -88,8 +111,15 @@ uint8_t sentSwitches[MAX_SWITCHES] = {SWITCH_LOW};

uint8_t nextSwitchIndex = 0; // for round-robin sequential switches

// flag to indicate that we need to change radio power when it's next safe to do so
bool pendingPowerChange = false;
// flag to indicate that we're expecting a telemetry packet
bool waitingForTelemetry = false;

// count of how many consecutive telemetry packets have been missed
uint8_t missedTelemetryPackets = 0;

// rssi thresholds for dynamic power increase and decrease
int16_t dynamicPowerRSSIIncreaseThreshold;
int16_t dynamicPowerRSSIDecreaseThreshold;


// Methods that need to be callable from the C interrupt handlers
Expand Down Expand Up @@ -233,6 +263,8 @@ GENERIC_CRC14 ota_crc(ELRS_CRC14_POLY);
GENERIC_CRC8 ota_crc(ELRS_CRC_POLY);
#endif

bool thisFrameIsTelemetry();
bool isArmed();


// ======== Interrupt Handlers ============
Expand All @@ -256,12 +288,6 @@ void TIMER2_IRQHandler(void)

NonceTX++; // New - just increment the nonce on every frame

if (pendingPowerChange)
{
pendingPowerChange = false;
radio.SetOutputPower(radioPower);
}

#ifdef ELRS_OG_COMPATIBILITY

HandleFHSS(); // experimental - can we do fhss here?
Expand All @@ -278,7 +304,29 @@ void TIMER2_IRQHandler(void)
// fhss is in txdone
#endif // ELRS_OG_COMPATIBILITY

SendRCdataToRF();
// Check if we're due for a telemetry packet
if (((uint8_t)ExpressLRS_currAirRate_Modparams->TLMinterval > 0) && thisFrameIsTelemetry())
{
// This frame is for telem, so don't attempt to transmit
// The rx was started from the txdone isr, so nothing to do here

} else {
// This is a normal RC frame. We don't expect to still be waiting for telemetry when we get here
if (waitingForTelemetry) {
missedTelemetryPackets++;
waitingForTelemetry = false;
}

if ((missedTelemetryPackets > DYN_POWER_MISSED_TELEM_PACKET_THRESHOLD) && (radio.currPWR < radioPower) && isArmed())
{
// We didn't get telemetry packets so we have no rssi/lq info for dynamic power
// Switch to the full configured tx power
missedTelemetryPackets = 0;
radio.SetOutputPower(radioPower);
}

SendRCdataToRF();
}
}
}

Expand Down Expand Up @@ -617,6 +665,10 @@ void ProcessTLMpacket()
if (TLMheader == CRSF_FRAMETYPE_LINK_STATISTICS)
#endif
{
// clear the flag and reset the counter
waitingForTelemetry = false;
missedTelemetryPackets = 0;

rssi = radio.RXdataBuffer[2];
snr = radio.RXdataBuffer[4];
lq = radio.RXdataBuffer[5];
Expand All @@ -627,7 +679,8 @@ void ProcessTLMpacket()
// use rssi * 100 in the filter for greater resolution

int32_t rssiF;
if (((int32_t)rssi * 100) < rssiFilter.getCurrent()) {
if (((int32_t)rssi * 100) < rssiFilter.getCurrent())
{
// when things are getting worse, just jam the new value into the filter
rssiFilter.setInitial(rssi * 100);
rssiF = rssiFilter.getCurrent();
Expand All @@ -638,12 +691,25 @@ void ProcessTLMpacket()

// printf("rssi %d, filtered %ld\n\r", rssi, rssiF);

if ((rssiF < DYN_POWER_MIN_RSSI * 100) && (radio.currPWR < radioPower))
// Order of tests is important for lq vs max rssi conditions since both could evaluate true and if
// so we want the LQ test to take priority. The tests are therefore in priority order, highest to
// lowest

if ((lq < DYN_POWER_LQ_PANIC_THRESHOLD) && (radio.currPWR < radioPower)) {
// Panic time, take the power directly to the configured max
radio.SetOutputPower(radioPower);
}
else if ((rssiF < dynamicPowerRSSIIncreaseThreshold * 100) && (radio.currPWR < radioPower))
{
radio.SetOutputPower(radio.currPWR + 1);
// printf("rssi %d rssiF %ld power up! %d\n\r", rssi, rssiF, radio.currPWR);

} else if ((rssiF > DYN_POWER_MAX_RSSI * 100) && (radio.currPWR > -18)) // XXX constant for min power
}
else if ((lq < DYN_POWER_LQ_THRESHOLD) && (radio.currPWR < radioPower))
{
// If we're losing packets it's worth boosting power even if the rssi is better than the threshold
radio.SetOutputPower(radio.currPWR + 1);
}
else if ((rssiF > dynamicPowerRSSIDecreaseThreshold * 100) && (radio.currPWR > -18)) // XXX find/add a constant for min power
{
radio.SetOutputPower(radio.currPWR - 1);
// printf("rssi %d rssiF %ld power down! %d\n\r", rssi, rssiF, radio.currPWR);
Expand Down Expand Up @@ -691,7 +757,7 @@ void HandleTLM()
// printf("starting rx\n\r");
// gpio_bit_set(LED_GPIO_PORT, LED_PIN); // for debugging, set the led pin high when listening
radio.RXnb();
// WaitRXresponse = true;
waitingForTelemetry = true;
}
}
}
Expand Down Expand Up @@ -747,11 +813,32 @@ void GenerateSyncPacketData()
uint8_t TLMrate = (ExpressLRS_currAirRate_Modparams->TLMinterval & 0b111);
radio.TXdataBuffer[3] = (Index << 6) + (TLMrate << 3) + (SwitchEncMode << 1);

radio.TXdataBuffer[4] = UID[3];

#else // not ELRS_OG_COMPATIBILITY
radio.TXdataBuffer[3] = ((ExpressLRS_currAirRate_Modparams->index & 0b111) << 5) + ((ExpressLRS_currAirRate_Modparams->TLMinterval & 0b111) << 2);
#endif // ELRS_OG_COMPATIBILITY

#ifdef SEND_TX_POWER_IN_SYNC

int8_t adjustedDBM = radio.currPWR;
#if defined(RADIO_E28_27)
// for e28-27, PA output is +27dBm of the pre-PA setting, up to a max of 0 input.
adjustedDBM += 27;
#elif defined(RADIO_E28_20)
// for e28-20, PA output is +22dBm of the pre-PA setting, up to a max of -2 input.
adjustedDBM += 22;
#endif

radio.TXdataBuffer[4] = adjustedDBM;

#else // not sending tx power, send UID[3] as before

radio.TXdataBuffer[4] = UID[3];

#endif // SEND_TX_POWER_IN_SYNC

#endif // ELRS_OG_COMPATIBILITY

radio.TXdataBuffer[5] = UID[4];
radio.TXdataBuffer[6] = UID[5];
}
Expand Down Expand Up @@ -1334,12 +1421,6 @@ uint32_t scaleRollData(uint16_t raw_adc_roll)
void ICACHE_RAM_ATTR SendRCdataToRF()
{
// printf("n %u\n\r", NonceTX);
/////// This Part Handles the Telemetry Response ///////
if (((uint8_t)ExpressLRS_currAirRate_Modparams->TLMinterval > 0) && thisFrameIsTelemetry())
{ // This frame is for telem, so don't attempt to transmit
// printf("t skip\n\r");
return;
}

uint32_t SyncInterval;
if (isRXconnected)
Expand Down Expand Up @@ -1527,6 +1608,12 @@ void SetRFLinkRate(uint8_t index)

isRXconnected = false;

#ifdef USE_DYNAMIC_POWER
// The dynamic power thresholds are relative to the rx sensitivity, so need to be updated
dynamicPowerRSSIIncreaseThreshold = RFperf->RXsensitivity + DYN_POWER_INCREASE_MARGIN;
dynamicPowerRSSIDecreaseThreshold = dynamicPowerRSSIIncreaseThreshold + DYN_POWER_DECREASE_MARGIN;
#endif

// if (UpdateRFparamReq)
// UpdateRFparamReq = false;

Expand Down Expand Up @@ -1885,6 +1972,11 @@ void runSafetyChecks()

}

/** Update the filter to match changes in the rate of telemetry packets
* If either the telemetry interval or the packet rate change then the rate at
* which the filter gets updated will change, and the filter needs to be reconfigured
* to match.
*/
void updateDynPowerFilter()
{
#ifdef USE_DYNAMIC_POWER
Expand All @@ -1897,7 +1989,7 @@ void updateDynPowerFilter()

const float packetRate = 1000000.0f / (float)ExpressLRS_currAirRate_Modparams->interval;
const float updateRate = packetRate / tlmRatio;
float cutOffHz = 0.5f;
float cutOffHz = DYN_POWER_RSSI_FILTER_CUTOFF_HZ;

// if the filter cutoff is too large a fraction of the update rate the filter becomes unstable
if (cutOffHz > (updateRate/8.0f)) {
Expand Down Expand Up @@ -2238,7 +2330,6 @@ int main(void)
if (isRXconnected && ((millis() - localLastTelem) > RX_CONNECTION_LOST_TIMEOUT))
{
isRXconnected = false;
if (statusIsArmed) pendingPowerChange = true; // will trigger the timer ISR to set the output power
}

// update LCD
Expand Down

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