Skip to content

fix(radio): fix SX1262 image calibration leaving radio on the wrong frequency #21

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
0x00001312 wants to merge 2 commits into
base: main
Choose a base branch
from
Open

fix(radio): fix SX1262 image calibration leaving radio on the wrong frequency #21

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
2ae435f
fix(radio): issue CalibrateImage from STDBY_RC, not STDBY_XOSC
0x00001312 Jun 27, 2026
5fa63d7
fix(radio): fix LoRa frequency stuck at default after first band switch
0x00001312 Jun 27, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
28 changes: 26 additions & 2 deletions src/radio/SX1262.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -197,7 +197,15 @@ void SX1262::waitOnBusy() {
unsigned long t = millis();
if (_busy != -1) {
while (digitalRead(_busy) == HIGH) {
if (millis() >= (t + 100)) break;
// CalibrateImage on a fresh (uncached) band can legitimately run
// longer than other opcodes. The old 100ms cap could give up
// while BUSY was still genuinely asserted — the chip ignores SPI
// while busy, so the SetRfFrequency write right after a band
// switch would land on a still-busy chip and get silently
// dropped, leaving the old frequency in effect. 1000ms is well
// beyond any documented SX126x opcode duration, so this only
// changes behavior in the case that was previously broken.
if (millis() >= (t + 1000)) break;
yield();
}
}
Expand Down Expand Up @@ -242,8 +250,24 @@ bool SX1262::calibrate_image(uint32_t frequency) {

if (_imageCalBand == band) return true;

standby();
// CalibrateImage must be issued from STDBY_RC per datasheet, same as
// Calibrate() above. standby() would enter STDBY_XOSC on this TCXO
// board, which leaves the image/PLL calibration for the new band
// invalid — symptom: after switching bands (e.g. Americas -> Europe),
// SetRfFrequency below appears to apply, but the chip stays locked on
// the previously-calibrated band's frequency until a later call skips
// this (now band-cached) step and re-issues a clean SetRfFrequency.
uint8_t mode_byte = MODE_STDBY_RC_6X;
executeOpcode(OP_STANDBY_6X, &mode_byte, 1);
executeOpcode(OP_CALIBRATE_IMAGE_6X, image_freq, 2);
// Same as calibrate() above: BUSY needs a moment to assert after the
// opcode before waitOnBusy()'s poll loop means anything. Without this,
// waitOnBusy() can return immediately (BUSY hasn't risen yet) while
// CalibrateImage is still running, and the SetRfFrequency that
// setFrequency() issues right after lands mid-calibration and gets
// dropped — chip stays on the old band's frequency even though
// _imageCalBand now (wrongly) claims the new band is cached.
delay(5);
waitOnBusy();
_imageCalBand = band;
Serial.printf("[SX1262] Image calibrated for %lu Hz (0x%02X 0x%02X)\n",
Expand Down