Micron Document
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| SparkN0de-git | SparkN0de |
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Node / ReticulumProjects / RNode_Firmware.git / commits / 5d2f0b9


Commit 5d2f0b93e3986046c95bcd5498c7e536c5415edc

󰉖 Browse tree at this commit

Parents : 180207a
Author : GlassOnTin <GlassOnTin@users.noreply.github.com>
Date : 2026-03-29T17:53:28+01:00

Fix SX1262 errata 15.4 (IQ polarity) and 15.1 (modulation quality)

Errata 15.4: SetPacketParams resets register 0x0736 to an incorrect
default for IQ polarity. For standard IQ (no inversion), bit 2 must
be SET after every SetPacketParams call. Without this, LoRa RX
demodulation can fail silently while TX continues to work — the
symptom mimics a hardware failure.

Errata 15.1: Register 0x0889 bit 2 controls modulation quality at
different bandwidths. It must be cleared for 500 kHz BW and set for
all others. The previous implementation was a no-op stub.

Both fixes are from the SX1262 datasheet errata (DS_SX1261-2_V2.1)
and apply to all SX1262-based boards.

Changes

1 files changed, 28 insertions(+), 3 deletions(-)

M sx126x.cpp +28 -3

Diff

diff --git a/sx126x.cpp b/sx126x.cpp
index c67a4df..f8da5fa 100644
--- a/sx126x.cpp
+++ b/sx126x.cpp
@@ -270,9 +270,24 @@ void sx126x::setPacketParams(long preamble_symbols, uint8_t headermode, uint8_t
buf[4] = crc;
buf[5] = 0x00; // standard IQ setting (no inversion)
buf[6] = 0x00; // unused params
- buf[7] = 0x00;
- buf[8] = 0x00;
+ buf[7] = 0x00;
+ buf[8] = 0x00;
executeOpcode(OP_PACKET_PARAMS_6X, buf, 9);
+
+ // SX1262 errata section 15.4: IQ polarity is inverted compared to
+ // SX1276. The SetPacketParams command resets register 0x0736 to an
+ // incorrect default. For standard IQ (no inversion), bit 2 must be
+ // SET after every SetPacketParams call. For inverted IQ, bit 2 must
+ // be CLEARED. Without this fix, LoRa RX demodulation fails silently
+ // while TX continues to work.
+ uint8_t iqreg = readRegister(0x0736);
+ if (buf[5] == 0x00) {
+ // Standard IQ: set bit 2
+ writeRegister(0x0736, iqreg | 0x04);
+ } else {
+ // Inverted IQ: clear bit 2
+ writeRegister(0x0736, iqreg & ~0x04);
+ }
}
void sx126x::reset(void) {
@@ -729,7 +744,17 @@ void sx126x::handleLowDataRate() {
}
// TODO: Check if there's anything the sx1262 can do here
-void sx126x::optimizeModemSensitivity(){ }
+// SX1262 errata section 15.1: Modulation quality with 500 kHz LoRa BW.
+// Register 0x0889 bit 2 must be cleared for 500 kHz, set for all other
+// bandwidths. Improves receiver sensitivity at non-500 kHz bandwidths.
+void sx126x::optimizeModemSensitivity(){
+ uint8_t reg = readRegister(0x0889);
+ if (getSignalBandwidth() == 500E3) {
+ writeRegister(0x0889, reg & 0xFB); // clear bit 2
+ } else {
+ writeRegister(0x0889, reg | 0x04); // set bit 2
+ }
+}
void sx126x::setSignalBandwidth(long sbw) {
if (sbw <= 7.8E3) { _bw = 0x00; }


──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────