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Introduce non-linear TX_GAIN_LORA (#8107)

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* Introduce non-linear TX_GAIN_LORA

Previously, our TX_GAIN_LORA setting was a single number, intended
to represent the signal gain going through a power amp (plus or minus
antenna, attenuator, and other parts of the RF chain).

It turns out the relationship between the input power (i.e. from an SX1262)
and total output power is often non-linear. While we fudged a 1dBm difference
here and there with existing chips, the Heltec v4 has a 5dBm difference in gain
depending on which end of the input power (and frequency) you are at.

To allow people to run their Heltec v4 at max power when legal, and future
proof our code, this patch introduced an optional array-based TX_GAIN_LORA.

Define NUM_PA_POINTS and set TX_GAIN_LORA to gain values for a given input
power in 1dBm increments, and all will work.

For linear systems, just continue to define TX_GAIN_LORA as a number.

Fixes https://github.com/meshtastic/firmware/issues/8070

* Remove temporary power limit on heltec v4

* Add function RadioLibInterface::checkOutputPower

* Ensure SX126x reaches minimum supported power.

* Keep it simple, instead.
This commit is contained in:
Tom Fifield
2025-09-30 08:20:39 +10:00
committed by GitHub
parent 777e11bad9
commit a3e6f16378
4 changed files with 25 additions and 3 deletions
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7
src/mesh/SX126xInterface.cpp
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@@ -80,6 +80,9 @@ template <typename T> bool SX126xInterface<T>::init()
RadioLibInterface::init();
limitPower(SX126X_MAX_POWER);
// Make sure we reach the minimum power supported to turn the chip on (-9dBm)
if (power < -9)
power = -9;
int res = lora.begin(getFreq(), bw, sf, cr, syncWord, power, preambleLength, tcxoVoltage, useRegulatorLDO);
// \todo Display actual typename of the adapter, not just `SX126x`
@@ -118,8 +121,8 @@ template <typename T> bool SX126xInterface<T>::init()
LOG_DEBUG("Set DIO2 as %sRF switch, result: %d", dio2AsRfSwitch ? "" : "not ", res);
}
// If a pin isn't defined, we set it to RADIOLIB_NC, it is safe to always do external RF switching with RADIOLIB_NC as it has
// no effect
// If a pin isn't defined, we set it to RADIOLIB_NC, it is safe to always do external RF switching with RADIOLIB_NC as it has
// no effect
#if ARCH_PORTDUINO
if (res == RADIOLIB_ERR_NONE) {
LOG_DEBUG("Use MCU pin %i as RXEN and pin %i as TXEN to control RF switching", portduino_config.lora_rxen_pin.pin,